Network

Network+ 2005 Training & Test Preparation Guide

Network + Training & Test Preparation Guide

Specialized Solutions, Inc. 20

Client/Server Network

Peer-to-Peer Networking

In a peer-to-peer network there are no separate computers that act as servers. All of the computers on the network can act as either clients or servers depending upon the needs of the user. This type of network is most often used when fewer than ten computers are involved.

A peer-to-peer network is simple and inexpensive to install. The computers are simply cabled together, and as long as each computer has an operating system capable of client/sharing (e.g. Windows 95 and up) they will be able to communicate via the network. In a peer-to-peer network all computers are equal.

A disadvantage of the peer-to-peer network is that since users are responsible for their own systems’ security, network security is unreliable. Also, a peer-to-peer network is difficult to expand.

Peer-to-Peer Network

Chapter 1 – Networking Fundamentals


Basic Network Structure (Topology) A network’s basic structure, or topology, refers to its physical layout, design, map, scheme, or diagram. As a network professional, you will need to know how to choose the network topology that will best suit the needs of your network. The type and capabilities of the equipment that will be used, future growth needs, and how a network will be managed are all potential problems that need to be considered when planning a network.

Setting up a network requires more than just cabling the computers together. Different topologies have different cabling requirements. NICs, (Network Interface Cards, also called Network Adapter Cards), connectors, how the computers will talk to each other (protocols), and even how the cabling is run through a building, are all determined by the topology used.

There are three standard topologies that a network professional needs to understand:

• Bus Topology

• Star Topology

• Ring Topology

Bus Topology

The simplest and probably the most used form of network topologies is the Bus topology (sometimes called a linear bus). The nodes (computers or devices connected to the network) are all connected along a single cable. This cable is called a trunk, backbone, or segment.

Devices on a Bus topology communicate by sending data to a specific address on the network (a device’s address). An electronic signal is sent out on the cable to all of the devices connected on the network. However, only the device whose address matches the address encoded in the signal will respond to the signal.

Only one computer at a time can transmit data on a Bus network or signals will collide and the transmission will fail. This means that the more computers that are connected to a Bus the slower the network becomes as devices are waiting to transmit or retransmit.

The Bus topology is a passive topology. Devices only listen for data being transmitted, they do not move the transmissions along. The signal is sent out on the cable and it travels from one end of the cable to the other. If not prevented, the signal would travel back and forth along the cable and cause what is known as signal bounce. While the signal is bouncing back and forth, it prevents other devices from sending data. To stop signal bounce, a component called a terminator is installed at each end of the cable. A terminator absorbs the signal and stops signal bounce.

In a Bus network, if the cable breaks, the network will go down and devices will not be able to communicate with each other.



Star Topology

In a Star topology, all devices are connected to a central point called a hub. It requires a lot more cable than the Bus topology, but the advantage is that if one computer (or the cable that connects one computer to the hub) goes down, the rest of the network will still continue to function. If the hub fails, however, the entire network will go down.

Star Topology

Ring Topology

In a Ring topology, the devices are connected in one continuous circle of cable. There are no ends to terminate. The data is transmitted around the loop in one direction and passes through each computer on the network. The Ring is not a passive topology like the Bus topology. The signal is actually boosted and sent on along the cable when it passes through the computers on the network. A disadvantage is that if one computer fails, it can affect the entire network.



With IBM Token Ring networks, the ring is actually in a special se

nd not prevent the network from Special Topologies

n

can understand some of these special topologies, you will need to know the difference between a physical and a logical topology. So far, we

ave been discussing physical topologies. These are the methods in which a network is actually wired. You will be able to see a physical topology. A logical topology, on the other hand, is how the network actually works. For example, some Ethernet networks today are wired using a using multiple hubs. This gives us a physical star topology.

owever, they operate between the hubs like a bus topology and are therefore a logical ng networks are physical stars and logical rings.

l

a Star Ring are connected in a star pattern by a main hub.

esh Topology

In the Mesh topology every device is connected to every other device by separate cables and has redundant paths. This is very expensive to install but it is extremely reliable because of the redundant paths.

type of hub called a Multistation Access Unit (MSAU). In thenetworks, a computer can fail afunctioning. In addition to the above topologies, today’s networking professional will encounter manynetwork topologies that are combinations of the above configurations. These are knowas Hybrid topologies. Before you

h

Hbus. Also, Token Ri

Hybrid Topologies

The Star Bus topology is a hybrid of the Star and Bus topologies. It consists of severaStar topology networks that are linked using linear Bus trunks.

The Star Ring topology is similar to the Star Bus, but the hubs in

M



Wireless Topology

A Wireless topology is one in which there aren’t any cables connecting the network e LAN or one which the LAN uses wireless technology between access

oints. Since each computer has its own connection to the wireless access point (WAP), the topology of a wireless network is that of an “invisible star”. . The benefits of wireless technology will be discussed at length in Chapter 4 of this book.

devices to thp





ng describe the way in which the computers and other devices on a network are connected. This is based on the media or wiring of the network. Another aspect of networks that is related to topology is the way in which the network is accessed by individual d devices connected to one media,

of a “party line”. The method that is used for an individual device to be network party line is called media access. The two most common network

Token Passing

Token passing is the method of sending data around a Token Ring topology. A token is passed along from device to device until it is received by a computer that needs to transmit. The sending computer grabs the token and encodes it with addressing information for the receiving computer and sends it out on the ring. It is passed along from device to device until it arrives at the computer whose addressing information matches the one encoded on the token, and the message is delivered. The receiving computer then sends the token back to the sending computer to let it know that it received the message. The sending machine then creates a new token to send around the ring that will be grabbed by the next device that wants to transmit data on the network. Since there is only one token, only one device at a time can communicate on the network.

Network Access The topologies that we have been discussi

evices. With severalwe create kindable to use thestandards are distinguished by their respective media access methods, they are called Token Ring and Ethernet. We will also cover access methods in more detail in the chapter “Network Protocols and Standards.”

Token Passing

Ethernet

Ethernet uses a system known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Carrier Sense means the network card listens to the cable for a quiet period during which it can send messages. Multiple Access means that more than one computer



can be connected to the same cable. Collision Detection is the ability to detect whether either message will arrive at their destination and both messages have collided in transit (n

will be retransmitted).

Collision Detection

t works on the same principals as Ethernet but operates at 10 times the speed of the original. Ethernet transmits at 10 Mbps and Fast Ethernet transmits at 100 Mbps.

Fast Ethernet

Fast Ethernet was developed to meet the increasing demands on networks. Fast Etherne



tworks. Today, hubs come in a variety of names depending on their function. The most common name used with Ethernet is a hub or a concentrator. With a Token Ring, they are called MSAUs (Multiple Station Access Units). Essentially, they are all the same, since they provide a common location for connecting the cabling of a network. Just remember, not all hubs are the same and you must use one that is designed to meet the needs of the network. Hubs can be classified as either passive or active.

Passive Hubs

A passive hub acts as a connection point only. Signals pass through the hub but are not regenerated or amplified. Passive hubs do not require any electrical power to function.

Hubs and Concentrators More and more networks are using hubs and they are pretty much standard equipment in today’s ne

Passive Hub – Patch Panel



Active Hubs

bs used today are active hubs. An active hub regenerates or amplifies a Most of the husignal when it is passed through. This type type of hub requires electrical power to function.

Active Hub

Hub-Based Networks

Hub-based networks are increasing in popularity. They have many advantages over other types of networks: 1) If a cable breaks only the portion of the network on that segment is affected. 2) Centralized monitoring of traffic and activity along with diagnostic capabilities are available. 3) A variety of cable types can be accommodated. 4) Expanding the network can be easily accomplished by using hubs.



is the sharing of resources. The two types of networks are LANs and WANs. A LAN is m and is the basic building block for larger networks. A WAN is not

geographically limited and typically has greater speed of communication than a WAN, and th the world’s largest WAN.

We also learned about the two basic network classifications of networks: the peer-to-peer network and the server-based network. It is important to know the differences between these two classifications and the advantages and disadvantages of each.

Topo to describe the log al shape of the connection of computers in a network. The three main types of topology are bus, star, and ring.

Be sure to complete the following exercises and review questions. If you are having trouble with any of these concepts, go back and review the chapter again.

Summary In this chapter we learned that the main reason for networking (as it relates to computers)

the smallest for

e Internet is

logy is a term we use ic



KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword Definition

Active Hub

Application

Application Server

Bus Topology

Client

Data

Fax Server

File Server

Hub

Hybrid Topology

LAN

Mail Server

MAN

Media

Mesh Topology

Network

Network Administrator

Passive Hub

Peer-to-peer

Peripheral

Print Server



Keyword Definition

Resources

Ring Topology

Security

Server

Server-based

Sharing

Star Topology

Token Passing

User

WAN

Wireless Topology



6. Name some advantages of a Peer-to-Peer network.

ges of a Server-based network.

10. Name the three basic topologies.

11. What is the difference between a physical and logical topology?

12. Name two media access methods.

Review Questions - Chapter 1

1. What are the key differences between a local area network (LAN) and a wide area network (WAN)?

2. What is the main reason for networking computers?

3. What is a “sneaker net”?

4. Name some advantages of having centralized documents.

5. What does MAN stand for and why is it no longer in use?

7. Name some disadvantages of a Peer-to-Peer network.

8. Name some advanta

9. Name some disadvantages of a Server-based network.

Chapter 2 – Network Operating Systems (NOS)


ems (NOS) Chapter 2 - Network Operating SystUp to this point we have focused on the design aspects of networking. Even if you have the best network design composed of the best hardware in the universe, if you don’t have the software to run it, it is just a pile of metal and plastic. You can get it all set up and

t without an operating system, it will just sit there.

e

perating systems designed to

ore popular network operating systems. We will also discuss their minimum requirements and interoperability

ifferences between server and client operating systems as well as

sets of software in order to function in

ftware). The operating system is also

turn on the power, bu

This chapter is all about the various operating systems with which a networking professional needs to be familiar. When we are talking about operating systems, what ware really talking about are network operating systems.

Network operating systems (NOS) are specialized ointegrate computers in a networking environment. Most of today’s client and server operating systems have a built-in network operating system. When we refer to the operating system in this chapter, we are referencing the built-in network operating system component.

In this chapter we will explore the features and benefits of the m

capabilities. The dpreemptive and non-preemptive multitasking will be covered as well.

What is an Operating System? Not that long ago, network operating systems were designed to operate on top of an existing operating system. A computer needed two a networking environment. Today, most networked computers run software that was specifically designed to run both the computer’s stand-alone functions as well as its networking functions.

Hardware resources such as RAM, processor time, hard disk space, and peripherals are all controlled by the operating system (the soresponsible for the running of applications (e.g. word-processing, spreadsheet, and database programs). The main objective is to make sure that the hardware and the applications are all compatible with each other, as well as the operating system.



Multitasking

means that the operating system can take control of the k’s permission. Non-preemptive multitasking is when the task

or

Preemptive vs. Non-preemptive

Multitasking, put simply, means that an operating system has the ability to perform more than one task at a time. A true multitasking (multi-processing) operating system is able toprocess as many tasks as it has processors. Most operating systems appear to be performing multiple tasks by alternating between tasks until they are all completed.

Preemptive multitaskingprocessor without a tasdecides when it is done with the processor. In non-preemptive multitasking, the processis never taken away from a task. Preemptive multitasking began with Windows 95 and the Intel Pentium processor. It is used on all of the latest operating systems.



hat is a Network Operating System (NOS)? A NOS is an operating system er software, such as BSD UNIX, Novell NetWare lient, or her computers over a ne

Peer-to-P

Many sm rking envi tilize the peer-to-peer network configuration. Peer-to-peer LANs are an excellent choice for the network that has less than ten compute of sec environment). It is certainly the most the net nly NICs and cabling will need to be pur ent this kind of network.

A peer-to is not a cl rk. Instead, each workstation may act as either a client or a server depending upon whether it is accessing resources on another workstation or if anoth ources. Usually this type of network only shares files and peripheral de s in use today are already capable of m is type of network.

Window

Windows 8 g systems that include a network operating system. Their new graphical interface and networking capabilities make them a vast improvem ir predec icon called the Network Neighborhood for desktop access of the network. All shared resources are arranged on a hierarchical basis and displayed in Network Neighborhood.

Plug-n-P has als ch easier. Windows 95/98 is also able to better identify NICs. To install a NIC with Windows 95/98 is as simple as installing the card, turning on the computer and answering questions. Then, all you have to do is share any directories and peripherals to the network, and you have a working network.

indows 95/98 also performs very well as a client with both the NetWare and Windows t is necessary to install the requester software (NetWare Client32

music. It protects critical files and will allow you to revert your system back to normal if anything goes wrong. Help and support is improved from Windows 98 and home networking is made easier than ever.

Wthat includes oth

, Microsoft Ctwork.

a similar program, to communicate with ot

eer LANs

aller netwo ronments u

rs and no needeconomical of

urity (such as a small officeworking choices. Usually o

chased to implem

-peer LAN ient/server-based netwo

er workstation is accessing its resvices. Most of the operating system

anaging th

s 95/98

95 and Windows 9 are operatin

ent over the essors. They use an

lay technology o made installing a NIC mu

WNT operating systems. Ifor Windows 95) with NetWare. With NT the only drawback is that you will not be able to utilize NT’s advanced security features because Windows 95 is not compatible with the NTFS file system.

Windows ME

Windows ME is the client operating system that has followed the Windows 9x operating systems. It is well-suited for editing home movies, moving photos to the Web, and archiving



Windows 2000 Professional is the client counterpart to Windows 2000 server. It features file protection, driver certification, remote OS installation, multilingual support, peer-to-peer support for W ypting File System), IPsec and Kerberos support. It also supports Microsoft Management Console (MMC) and group policies.

me

s

Windows 2000 Professional

indows 9x and NT, EFS (Encr

Windows XP Ho

Windows XP Home edition is the newest edition of Microsoft’s OS for home users. It allows for faster user switching, a simplified visual design, It also uses System Restore,like ME, which allows for safety when installing additional software or making changeto the computer’s configuration. It, like the rest of the client OS software mentioned here, is equipped to be networked easily.

Other Peer-to-Peer LANs

The following table lists other peer-to-peer LAN software and their manufacturers that the networking professional may come across in real life but are unlikely to be on the test:



Software Name Manufacturer

10NetPlus Digital Communications Associates, Inc.

AppleTalk Apple Computer

Easy Net LanMark

GV LAN OS Grapevine LAN Products

LANsmark D-Link Systems

LANsoft ACCTon Technology

LANStep Hayes Microcomputer Products

LANtastic Artisoft

NET/30 Invisible Software

Network OSCBIS Peachtree

OS/2 Warp IBM Corporation

Personal NetWare Novell

POWERLan Performance Technology

ReadyLink Compex

WEB WebCorp

Server/Client Software

In a peer-to-peer network, the computers act as both a client and a server. However, it is necessary to have an operating system that can perform in this environment. In a Server-based network, the purpose of a network operating system is to connect all devices on a network (computers and peripherals) and to coordinate their usability. This can also provide accessibility and security for all devices on a network. Some network operating systems require that different versions are installed depending on whether a computer is the server (provides resources remotely over a network) or a client (uses resources locally).



networking software that must be considered:

reso cdata n manage a network. Unlike m server software includes services for the

manage users from a central location. Users are required to

et up the accounts to determine who gets privileges to what resources and change them as needed (including denying access). The server keeps track

er. At the very least, the server should be attached to an uninterruptible power supply (UPS). Some networks even cluster server so that more that one server can share a database of information. This

There are two types of

• Client Software

• Server Software

Client Software

If you type a command for your stand-alone computer to perform a task, the command isprocessed over the computer’s internal CPU via the computer’s local bus. However, if you were requesting resources or services that exist on a remote server, the operating system has to have the capability to redirect (forward) the request away from the local bus, out onto the network, and to the server. The component that handles these requests iscalled the redirector.

Server Software

As their name implies, Servers exist to serve. They process requests from clients for ur es such as files and peripherals. They are the storage facility for the bulk of the i a network environment and as such are an excellent point from which to centrally

ost client software, following:

• Managing User Accounts

• Security

• Data Protection

Managing User Accounts

Servers make it possible toenter a password before they can log on and gain access. Administrators set up and manage user accounts and passwords.

Security

Administrators can s

of who is logged onto a network and what resources have been (or are being) accessed. Network security is discussed in greater detail in Chapter 10.

Data Protection

As we already discussed, most of the data is stored on the server. This makes it an excellent point from which to perform regular backups. Most network administrators provide some sort of fault-tolerance system on the serv



of the server resources as well as fault tolerance if one server

s called the requester) is responsible for forwarding requests away from the local bus and redirecting them to the server.

work operating system that intercepts

redirector is to make network resources look like local resources to

tion program believe that it is simply working with a very large hard drive or with a local

ing about networks.

provides for load balancingwere to fail.

The Redirector (Requester)

The redirector (in Novell NetWare this i

Basically, it is a section of code located in the netrequests and determines if they are local requests, or if they need to be redirected to the server.

The purpose of theapplication programs. It does this by assigning drive letters, called drive designators, to resources. If it is a local designator (drive C: for example) the request is passed on to the local bus. If it is a network designator the request is forwarded to the server, which opens the file or transfers the print job to the network printer, etc. This makes the applica

printer. It does not need to know anyth



NOS Packages There are a mul k operating systems available for use. Each of them has its own advantages and disadvantages. In this section, we will take a closer look a some of the more pop

Novell NetWare

The NetWare operating system e. In the past, it was the most popular se t it is arket share to Microsoft servers every year. It is a reliable operating system that provides performance and security. The earliest version ed to operate on 286 machines. Versions 3.12 and 4.11 operate on 386, tranetWare. It is Novell’s push to net, which is like the Internet but wit w on the market. NetWare is based upon the industry standard X500 director Ware is administered through NetADMIN, which is a DOS-based utility, or through NWADMIN.EXE, which is a Windows-based utility. It may be installed in either the client or server format.

• NetWare’s popularity is due largely to its ability to provide services across multi-operatin

NetWare Direc

NDS (NetWare tWare operating system. It is a hierarchically o base that provides security, name service, messaging, routing, web-pu ment, and file and print services. Organization of network resources such as users, groups, serv ndled with NDS. With NDS’ single point logon, a user may log network and gain access with all o

NetWare File S

The NetWare file server hard drive may be mapped to a client and the client machine will recognize the drive as a logical drive and be able to access it as it would any other drive

The e will always be data in any network to which accesnetw r curity provides authentication and verification of user naTru e d of access they have. Directory and file attributes are used to set the types of access for a file d d, or changed. See Cha e

titude of networ

ular ones.

has been around for a long timrver operating system, bu losing m

(2.2) was design 486, or Pentium machines. Version 4.11 is called In gain market share and is a way of creating an Intra

hin a network or company. Version 6.5 is noy architecture. Net

g system environments.

tory Services (NDS)

Directory Services) is the core of the Nerganized datablishing, manage

ers, and volumes is also haon from anywhere on the

f their assigned rights and privileges intact.

ervices

in the computer.

NetWare Security

purpose of a network may be to share resources, but thers must be restricted. NetWare provides more than adequate

o k security by using a combination of approaches. First, login seme, password, time, and account restrictions.

ste rights regulate which directories and files a user can access, as well as what kin

or irectory such as viewed, copied, shared, non-shareable, deletept r 10 for more information on network security.



r

o be a network wide E-mail system.

her ou

NetWare Print Services

NetWare Print Services can support up to 256 printers. The file server and the print servecan be the same computer. Print requests are first routed to the file server, next to the print server, and finally to the printer. Printers may be attached to the server, a workstation, or directly to the network.

NetWare Message Handling Service (MHS)

MHS may be installed on any server and configured tIt is compatible with E-mail programs such as Novell’s GroupWise and Microsoft Mail, as well as others.

NetWare also provides a method of using simple commands to send messages to otusers on the network. You can send messages to individuals or to groups very easily. Ycan even send messages to everyone in a group, except an individual workstation.

NetWare Minimum Requirements

The following are the minimum installation requirements as specified by Novell for installing their server software:



lient Software

The client software may be installed on any computer running any of the following:

• Macintosh 6.0 or later and the NetWare Client32 for Macintosh OS

Version 2.X:

CPU 286 or higher

RAM 2.5 MB

Free Hard Drive Space 20 MB

Version 3.X:

CPU 386 or higher

RAM 6 MB


Version 4.X:

CPU 386 or higher

RAM 16 MB


Version 5:

CPU Pentium Class or higher

RAM 64 MB


C

• DOS 3.1 or later and the NetWare Client32 for DOS

• MS Windows 3.0 or later and the NetWare Client32 for DOS

• OS/2 1.1 or later (Standard or Extended Edition) and the NetWare Client32 for OS/2

• OS/2 2.11 or OS/2 Warp and the NetWare Client32 for OS/2



to nt

nd early 90s, its popularity

ating system environments, but it does have several advantages. The services provided by the server are more powerful and it is easier for

The NT Kernel, which as at the base of all Microsoft’s servers, actually evolved from a

T 1993. Today, Windows NT has two versions: Server (the server

software) and Workstation (the client software). Although Server and Workstation can d-alone or network systems, Server is much more powerful so rk management. The newest of these server operating systems,

Windows may be shared by using a simple file sharing method similar to sharing files on is type is performed by each workstation or server publicly

k. The attributes such as Read, Change, Full Control, or r

the

long as they are in different partitions on the hard anyone not using NTFS cannot recognize NTFS

o the publicly shared files mentioned earlier.

NetWare Interoperability

As the word implies, interoperability simply means the ability of an operating systemoperate with other systems. As we’ve already discussed, NetWare is extremely efficieat operating with other systems. The NetWare client can be installed with almost any other operating system. Problems do occur when trying to operate within the Windows NT domain, but Windows NT contains services such as NWLink and Gateway Service for NetWare (GSNW) that allow them to work together effectively.

Microsoft Windows NT Network Operating System

While NetWare was the network operating system of the 80s ais being replaced by Microsoft Windows Servers. Unlike NetWare, Windows combines the operating system and the network operating system into one. This makes it more difficult to work in multi-oper

programmers to develop software that takes advantage of Microsoft’s server/workstation technology.

project that was jointly developed by IBM and Microsoft (OS/2). Microsoft released theWindows NT operating system and a network operating system version, Windows NAdvanced Server in

both operate as either stanthat it may provide netwoWindows 2000 Server and Windows Server 2003, offer even more advantages and stronger security than their predecessors.

Windows File Services

Like NetWare, the Windows servers may be configured to store each workstation’s directories in order to provide centralized data management and backups. Files in

a peer-to-peer network. Thsharing a directory on the networNo Access may be set on the directory. You must have administrative privileges in ordeto share anything on a Windows network.

In order to take maximum advantage of the security features in Windows , another security method must be utilized. With this method, you may assign directory and file-level permissions to the data, allowing restricted access to individuals or groups. The NTfile system (NTFS) must be utilized in order to take full advantage of Windows security features. The advanced security features of Windows are not available if you choose DOS file system (FAT - File Allocation Table) during installation. It is possible to useboth the NTFS and FAT file systems asdrive. A disadvantage of this is thatdirectories, and is limited t



se e permission to access a resource.) Installing a network

printer is just like installing a local printer, except that you are asked if it is to be a

to any printer that you want to use (assuming that

you have the appropriate permissions).

ork Services

Server Service provides access to network resources.

Interoperability

As Novell NetWare was the “big kid on the block” when NT came on the scene, Microsoft wanted to make NT as compatible with NetWare as possible. This trend continued with the latest Windows server operating systems (Windows 2000 Server and Windows Server 2003. The following is a list of services included with Windows Server software to ensure NetWare compatibility:

NWLink is actually a clone of Novell’s IPX/SPX protocol and is used for communication between Microsoft and NetWare.

Windows Server Security

Security was a major concern in the development of Windows Servers, especially with the latest Windows Server 2003 family. Microsoft uses domains to control access and authenticate users and computers. A domain is simply a group of users, computers, and resources with a shared security database. At least one domain controller is assigned to each domain. A domain controller is a server that maintains and manages all accounts, permissions, and user rights. Rights must be assigned to users in order for them to use any resources or perform any tasks in the domain.. See Chapter 10 for more information on network security.

Windows Print Servers

Any workstation or server may perform as a print server in a Windows network. A printer need only be shared to the network to be accessible to anyone on the network. (Of coura user still has to be assigned th

network or local printer. Even if you are installing a local printer, you are given the option to share it to the network. Remember, more than one printer can be installedmachine. Printing is as easy as selecting the

Windows Netw

There are many services available in Windows to manage network flow:

Messenger Service monitors the network and provides pop-up messages for the user.

Alerter Service sends the notifications that are monitored by the messenger service.

Browser Service provides a list of all available domain and workgroup servers.

Workstation Service is the redirector service..



orkstations to use file and print services on a NetWare server. It can be installed on the Microsoft client to allow it to connect the Netware server directly. Installing CSNW automatically installs the NWLink protocol as well.

FPNW (File and Print Service for NetWare) is a utility that enables NetWare clients to access Microsoft file and print services. This software is not included with Netware but can be purchased separately.

DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems. It allows Novell NDS computers to be managed just as Microsoft domain controllers.

Migration Tool for NetWare is a tool used to convert from NetWare to Windows. Its purpose is to move (called migrating) NetWare account information to Microsoft’s domain controller.

Windows 2000 Server

Windows 2000 server is the server-side OS to Windows 2000 Professional. Probably the biggest feature in Windows 2000 server is the addition of Active Directory. Active Directory is a directory service that stores information about objects on a network and makes this information available to both users and administrators. It allows for a single logon to access resources anywhere on the network. It also offers an improved version of NTFS and fault tolerant versions of RAID on dynamic drives. Group policies can be utilized with server 2000, which govern what users can see and do on the network.

Windows Server 2003

Windows Server 2003 is the latest in the line of Microsoft server operating systems. It provides all of the advantages of Windows 2000 Server, but it adds many features that are designed exclusively for security. Windows Server 2003 offers a more secure Web Server (IIS 6.0) than the previous version in Windows 2000 (IIS 5.0). In addition, it has more “locked down” security templates that make it less likely that users will try to go around the security. In fact, Windows Server 2003 is the first Windows server that was built primarily with security in mind. Previous Microsoft server operating systems were built to serve and then had security features to protect them. In contrast, when using Windows Server 2003 you typically must remove or configure security boundaries in order to get the server to...well serve.

UNIX Operating Systems

UNIX stands for UNiplexed Information and Computing System. Even though UNIX was not designed as a network operating system it can be, and is, used as such. UNIX is a

GSNW (Gateway Services for NetWare) provides the gateway between an Microsoft domain and the NetWare server. This is necessary because all Microsoft client workstations in a domain must connect to a NetWare server through a single contact point. Network performance will decrease as the number of computers accessing the gateway increases. Installing GSNW automatically installs the NWLink protocol as well.

CSNW (Client Services for NetWare) is the Microsoft service that allows w



bulky operating system. It is primarily used on minicomputers and has many features that the engineering and scientific environments.

em

e is UNIX

can , OS/2, UNIX, or Macintosh System 7 for its operating system. A file redirector

NES is a client/server-based network operating system. At one

lled

sharing.

UNIX interface. At its

inception, Linux was designed to be less expensive than UNIX; in fact the software is any

means that it can be ns

are favored in

UNIX is a multi-tasking, multi-user, general-purpose operating system. A UNIX systconsists of a host (a central computer) with terminals for the users. These terminals arenot stand-alone computers, but rely solely on the UNIX host for resources. Softwaravailable, however, to convert the UNIX host into a file server. The multi-taskinghost will run this software as just another application. The UNIX-based workstation run DOSis used to allow the workstation to store and retrieve UNIX files as if they were in the original format.

Banyan VINES (Virtual Integrated Network Service)

Like Windows, Banyan VItime, it was an extremely popular network operating system, but has lost market share since the arrival of NetWare.

VINES was originally based on UNIX and has a directory services application caStreetTalk layered on top. StreetTalk provides directory, security, and messagingservices, as well as file and printer

Like Novell NetWare, VINES is a great performer in multi-operating system environments.

Linux is another operating system similar to UNIX. It is a publicly open system that hasmade it popular among enthusiasts already familiar with a

available for a free download. It uses a GUI (graphical user interface), TCP/IP, and mother features associated with an OS. It is available on both Intel (PC) and PowerPC (Mac) platforms, as well as others. Linux is open source, whichchanged by a software programmer. Because of its open source nature, many variatioof Linux have been created over the years such as Caldera and Red Hat.



veloped by Apple Computer in 1984. In conjunction with er became known as the mouse and the first GUI display.

The Mac OS X is the most current o tem used in conjunction with the Apple computer (at the time of the writing of thisis called PowerPC. Macs are known for being used primarily in video or graphic production, but users also use them personally, both at home and on the go.

The Macintosh ("Mac") was deXerox, they developed what lat

perating sys book), and the processor used in Apples today



y ifeblood of the computer. Without an operating system a

computer is just another pile of metal and plastic. Network operating systems allow a put

operati s also function as the network operating system. There still are numerous LANs that use a network operating system over a conventional operating system.

resources to others on the network) or a client (when sharing the resources of another computer on the network). In a server-based network, the client computers rely on the

Server and client machines typically use different operating systems. Novell’s NetWare allows for client machines to use a variety of operating systems. Windows NT has Server

advantages of the server-based network are increased security, centralization of administration, and data backups.

is the Redirector (called the Requester in vell function of the redirector is to determine whether a requested

resource is located locally (on the client computer) or exists on the server (remotely). The redirector then routes the request to the proper bus accordingly. With the redirector, an

It is im ssional to know the major network operating systems used today, such as Novell NetWare and Windows server operating systems, and at least be familiar with others, (UNIX, Banyan VINES, etc.).

Be sure to complete the following exercises and review questions. Study through the chapter again if you need to.

SummarOperating systems are the l

com er to function in a network environment. Today, the most popular network ng system

In a peer-to-peer network, the computers may function as either a server (when sharing

server for their resources.

software for the server and Workstation software for client machines. The main

A key component in a network operating systemNo NetWare). The

application is unaware that it is working from a network.

portant for the networking profe



KEYWORDS Exercise Keyword Definition

Client Software

CSNW

DSMN

FAT

File Server

GSNW

Interoperability

MHS

Linux

Macintosh

Multitasking

NDS

Non-Preemptive Multitasking

NOS

NTFS

NWLink

Preemptive Multitasking

Print Server

Redirector/Requester

Security

Server Software

UNIX



eview Questions

1. What is the difference between an operating system and a network operating system?

2. What is the difference between preemptive and non-preemptive multitasking?

3. What is the purpose of the redirector?

4. NetWare is designed as an operating system that will overlay _____________ environments.

5. What is NDS?

6. What are the minimum hardware requirements for installing Novell NetWare version 5?

7. Define interoperability.

8. Unlike NetWare, Windows NT combines the _____________ and the ___________________ into one.

9. What is NTFS?

10. What is a domain?

11. What are the minimum hardware requirements for Windows NT Server?

R



12. Name some of the services and protocols that Microsoft included with Windows

oups as an operating

NT to ensure interoperability with NetWare.

13. What OS is similar to UNIX and is a publicly open system?

14. What type of computer was developed by Apple computer in 1984?

15. What type of network would utilize Windows for Workgrsystem?



Chapter 3 – The OSI Model and Communication Standards


ommunication Chapter 3- The OSI Model and CStandards In this chapter you will learn about the OSI (Opit is and its primary function. You will learneach function, and which devices function at 802 standards as well as touch on various protocols and how they relate to the OSI Model. The OSI model and IEEE 802 Standards are a big part of the Network+ exam.

The Seven Layers of Network Communic

en System Interconnection) model, what about which layer of the OSI model handles each layer. We will also discuss the IEEE

ation

rganization (ISO) released a

cate with one specifications allow hardware and software manufacturers to develop

model is designed as a framework ilar computer systems across a

y in use.

as

involving how network devices will contact each other,

nsmissions are received correctly by the recipient. Even how the

ned within these specifications.

The Open Systems Interface (OSI) model is the most commonly referenced standard inthe networking industry today. The International Standards Oset of specifications for connecting devices on a network in 1978. These specifications were updated in 1984 to what we know today as the OSI model. The purpose of these specifications is to describe how network hardware and software communianother. These products that are compatible with each other. The OSIthat allows communication between similar and dissimnetwork.

The OSI Model was created after many of the protocols it represents were alreadAs a result, some of the information regarding these protocols may appear to be inconsistent with the OSI Model.

There are seven steps required to prepare data for transmission between the sending application and the receiving application. The OSI model represents these seven stepsseven layers. These layers are used extensively in network environments and it is imperative that the networking professional understand the different layers and their functions.

The OSI model defines the rulesand how they will communicate if they are using different languages. The OSI model also defines how a device knows when to transmit; when not to transmit; and how to make sure that traphysical media is arranged and connected; how the data will flow (at what speed); and how bits are represented on the medium are defi



The Seven Layers of OSI

The first thing you should notice is we’ve listed the layers from the top down. This modelis usually represented in this way because we refer to the layers as upper and lower layers, depending upon their functions.

network

lude file, print, and messaging

sible for communication between a

access a

Seven Layers of the OSI Model The following is a summary of the seven layers of the OSI model starting with the top layer:

Application Layer

This layer of the OSI Model defines how services or applications interact with the network.These services incservices. Error recovery may also be a function of the Application layer. The Application layer is responuser’s application and the network. This is not the actual application or program, simply a support layer that allows an application to use the network by acting as a translator. This is the layer that allows users to send E-mail, transfer files across the network, or



a format that is compatible with the computer. This layer is also responsible for data compression, protocol conversion, (so that an IBM compatible

mputer.

and ending connections. Each connis called a session. The Session layer uses a nam

ines who can transmit, or receive, and when. The Session layer organizes data ese checkpoints ensure that

make it possible to limit retransmissions in the event of a

nication.

t.

ackets from the Session layer e being sent to the

are too small, they will be combined. If

network database. This layer enables computer applications to communicate with applications on remote machines as if they were local.

Presentation Layer

The Presentation layer is the translator for the network. It translates data into a format that is compatible with the network, and then the Presentation layer of the receiving computer translates the data back into

computer may communicate with a Macintosh, etc.) character set conversion, interpreting graphics commands, bit ordering, and data encryption.

The network redirector operates at this layer. The redirector is responsible for making network services appear to be local services to a co

As its name implies, it presents data to the application layer. The presentation layer acts as a translator between an application’s native format and the network.

Session Layer

The Session layer organizes the flow of data between devices. This layer is responsible for establishing, managing, ection

e lookup service such as NetBIOS to identify and establish sessions between two computers. It is also responsible for security and other functions that allow two applications to communicate over the network.

The Session layer controls the communication between the two computers and determsynchronization and also inserts checkpoints in the data. Thall data is sent (or received) andnetwork failure during transmission. Only the data after the last transmission will have to be retransmitted after a failure.

Sessions may be established using simplex, half-duplex, or full-duplex commu

Transport Layer

The Transport layer is responsible for the error- free delivery of the transmitted data. It provides a logical connection between the two devices. The Transport layer is also responsible for packaging, and un-packaging the data for transporIn short, it will break the data into packets, add any addressing information and error correction information, and prepare it for its journey.

The Transport layer is responsible for delivering data that is in sequence, without duplication, and error free. The Transport layer accepts pand repackages them. It is responsible for resizing them befordestination computer. For example, if the packets



y will be broken into smaller packets. The Transport layer of the destination computer reassembles the data (returns it to its original state) and checks for

d does not send any

more data until it receives the acknowledgement for the previous transmission. If the

received, it will be un-packed, stripped of its addressing information,

asort out the problems and request that

or control and other protocol-dependent features. UDP is a connectionless protocol. When you are

to construct the network plays an important role at this layer. The network

akes routing decisions for transmissions that are further away than a single link. It translates logical network addresses into physical machine addresses and

er est acceptable frame size on a network. For example, the largest frame size

n an Ethernet is 1,518 bytes and the smallest is 64 bytes. This layer also reassembles the data be s s and NICs functio i

IP and IPX are Network layer protocols.

Data Link Layer

The Data Link layer is the second lowest layer in the OSI model. It receives a packet from the Network layer and packages it into what is called a frame. Its head ress of the sending and destination NIC cards. (These addresses are hardwired onto the NIC by the manufacturers.) It also includes control information such as frame type, segmentation information and routing information.

they are too large, the

errors and duplications. Once the data is reassembled, the destination computer will senan acknowledgement that the data was received. The sending computer

sending computer does not receive an acknowledgement, it will retransmit after a specified amount of time.

When the data ischecked for errors, and then assembled and sent up to the Session layer. In an ideal world, all data packets will be sent and retrieved inan error occur, however, the Transport layer will missing packets be retransmitted.

TCP and UDP are Transport layer protocols. TCP is a connection-oriented protocol. When you are using a connection-oriented protocol, the Transport layer is responsible for the guaranteed delivery of packets. This is accomplished through various err

n orderly, error free manner. Should

using a connectionless protocol, delivery of packets is not guaranteed. Connectionless protocols are faster, but connection-oriented protocols are more reliable.

Network Layer

The hardware that is used

layer handles all the routing information as packets travel from one network to another.

The Network layer is responsible for communication between computers via their IP addresses. This layer m

determines the best route to the destination computer. This controls network congestion,especially on large intranetworks where there may be more than one way to reach a destination.

This layer is also responsible for breaking packets into smaller chunks, if they are largthan the largo

fore pa sing it up to the Transport layer on the receiving side. Routern on th s layer.

er includes the hardware add



In addition, the Data Link layer is responsible for error-free transmissions. It adds a includes the CRC (Cyclic Redundancy Check). The CRC is

e not

/IP is

puters.

for an individual computer or not. If it is, it accepts the data and passes it up to s the data.

y

e two

e upper OSI layers. The Logical Link Control

hat

A/CA), Token Passing, and Demand Priority.

is

e

st). The manufacturer is assigned blocks of numbers to assign to NIC cards.

pied to RAM when a NIC is initialized.

he following is an example of a MAC address:

trailer to the frame that simply a calculation that assigns a value to the frame. If the Data Link layer in the destination computer comes up with the same value when it receives the frame, it assumes the data was not damaged in transmission and sends an acknowledgement to thsending computer. If the calculation does not check out, the destination computer will send an acknowledgement. When the sending computer does not receive and acknowledgement, it will automatically resend the packet. In this way, TCPsomewhat “self healing”.

In a broadcast network such as Ethernet, the data is sent out on the wire to all comThe frame is accepted by the Physical layer of all of the computers on the network and passed up to the Data Link layer. It is the Data Link layer that determines whether the message is the next layer. If it is not, then it discard

The IEEE Committee thought that the Data Link layer needed to be further defined. Theaccomplished this by splitting the Data Link layer into two sub-layers.

Logical Link Control (LLC)

The Logical Link Control (LLC) sub-layer of the Data Link layer is the upper of thsub-layers. It is responsible for connecting two computers on a network and maintaining that link.

The LLC sub-layer provides SAPs (Service Access Points) that are used by other computers to transfer information to thlayer is concerned with managing traffic over the physical medium. It identifies a line protocol, such as SDLC, NetBIOS or NetWare and may also assign sequence numbers to frames and track acknowledgements. The IEEE 802.2 standard defines how this takes place.

Media Access Control (MAC)

The Media Access Control (MAC) sub-layer of the Data Link layer controls the way tmultiple computers share the same media channel. The way that a network shares the channel is called its carrier access method. The three main types of access methods are Contention (CSMA/CD & CSM

This sub-layer communicates directly with NICs using the MAC address. The MAC address is another name for the 12-digit (6 byte or 48 bits) hexadecimal address thathardwired on the NIC by the manufacturer. It uniquely identifies devices on the same medium. The first 3 bytes (6-digits) identify the manufacturer, (they are the vendor codthat is assigned to a manufacturer by the IEEE Committee) and the last 6-digits identify the NIC (hoThe combination of these numbers assures that each NIC that is manufactured (by anyvendor) will have a unique MAC address. Although quite rare, it is not unheard of for these addresses to be duplicated even with these precautions having been taken. MAC addresses are co

T



00-00-13-35-FD-AB

The first 3 bytes (00-00-13) identify the manufacturer of the card. The last 3 bytes (35-FD-AB) are the Device ID that is unique to the associated Vendor ID.

Bridges operate at the Data Link layer. Bridges are devices that connect network segments and filter data using MAC addresses. Switches, which are intelligent hubs that use MAC addresses to send packets, data work at the Data Link layer of the OSI model.

Physical Layer

The Physical layer is the bottom layer of the OSI model. It is the only layer of the OSI model that communicates directly with its peer on another computer. It is responsible for the mechanical and electrical functions of transmitting data over a network. It converts the data into the raw bits and signals (1’s and 0’s) that are actually transmitted over the network medium. The Physical layer of the receiving computer converts the bits back into frames.

The Physical layer is not concerned with the contents of the packets, it is only concerned with the physical elements of the network and the transmission and reception of signals. It specifies such things as how many pins a network connector will have, and what each one will do. It identifies the NIC, synchronizes the data, and determines when and how data may be transmitted.

Point-to-point and multipoint connections are addressed at the Physical layer. Point-to-oint communication is the process of one device communicating with one other device .

Multipoint communication is the process of one device communicating with multiple devices on a network. Point to point communication is often used between switches and routers on a network.

The physical characteristics of a network will affect the specifications of the Physical layer. For example, an Ethernet network using UTP would have different specifications than an Ethernet network using Fiber Optic cable.

Repeaters, hubs and transceivers, all operate at the Physical layer of the OSI model.

Note: For more information on the OSI Model, visit www.iso.ch/

p

.





plete a whole task. This is called a protocol stack, or suite. Each protocol receives services from the layer directly below it, and provides services to the layer directly above it.

TCP/IP is a common example of a protocol stack. In order for computers to communicate with each other they need to be using the same protocol stacks. In this way even completely dissimilar systems running different operating systems will be able to communicate. Each protocol will communicate with its peer or equivalent on the other computer.

Communication Between Peer Layers

Most network models utilize this layered architecture. The affect of this layering is that communication is seemingly only taking place between the associated layers of the two computers. Even though the data is passed down through the sending computer’s layers, over the network medium, and up through the receiving computer’s layers, in effect there is a logical or virtual connection made directly between the two associated layers.

This is accomplished by each layer (with the exception of the top and bottom layers) adding a header to the message (or removing it on the receiving end) before passing it down (or up) to the next layer. Headers contain instructions for tasks that need to be

erformed at that level. For example:

You send a request for services to the server. You are communicating directly with the Application layer. (Remember, the Application layer is not the actual application, simply a support layer to allow applications to perform network functions.) The request is in the form of a packet. The request is then passed to the Presentation layer where a header is added to the message. The Presentation layer passes the modified packet down to the Session layer, which also adds a header and passes the packet down to the Transport layer. This process continues until the packet reaches the Physical layer. The Physical layer does not add a header, it simply converts the packet into a bit stream and sends it out onto the network medium.

When the destination computer receives the data, the process of moving through the layers is reversed. As the packet travels up through the layers, each layer reads and performs the tasks specified in its peer’s header before passing the packet up to the next layer. When it arrives at the Application layer of the destination computer, the data is back in its original form so that it may be interpreted by you and the request is considered processed.

In addition to reading the headers and performing the instructions, each layer is also responsible for adding or removing headers so that the data is ready to be interpreted by the next layer.

Protocol Stacks When more than one protocol is necessary to accomplish a task, protocols can be layered so that specific protocols handle their appropriate subtasks at specific layers of the OSI model. These subtasks are stacked in such a way that together they com

p


Note: Packets (also called service data units) are made up of data and headers acquired from upper layers. Because of this, they are sometimes referred to by different names at different layers. The term packet is appropriate to all of the layers,but the following table lists the other names that might be associated with them at the various layers:

Physical Layer Signals or Bits or Data Stream into Frames

Data Link Layer Frames into Packets

Network Layer Frames or Datagrams into Segments

Transport Layer Segments into data

Session Layer Data

Presentation Layer Data

Application Layer Data into Data Files or Messages




ust keep in mind that it was created after many his means that if you were to attempt to

tocol or a standard directly to the OSI model, it would not match.

s of

odel, we can better understand how they communicate across the layers.

avel from one computer to another on a network from the Application layer to ceiving

as col

OSI and the Real World When working with the OSI model, you mpopular protocols had already been developed. Tmap a pro

In fact, some of the components or layers may actually do the work of several layerthe OSI Model, as in the case of the TCP/IP protocol. Also, the OSI Model is not a protocol. Its purpose is to provide a graphical image of how network protocols work together to provide communication between two computers. By relating various protocolsto the OSI m

Data will trthe Physical layer on the sending computer, then to the Physical layer on the recomputer and back up to the Application layer. This communication will take placelong as both computers are using the same protocols. The various layers of the protoare communicating as though they have virtual connections.

Flow of Data

As part of the Network+ Certification program, you will need to know the seven layers of the OSI model. The following mnemonics are commonly used to help remember the layers:



Mnemonic OSI Layer Mnemonic

Away Application All

Pizza Presentation People

Sausage Session Seem

Throw Transport To

Not Network Need

Do Data Link Data

Please Physical Processing

No matter how y different layers and the tasks for nsible. Keep in mind that it isn’t actually the

at perform e appropriate hardware or software that does the work. I model s ch functions need to be completed at each layer and

protocols h layer. This is so that different types of computers fferent ty n communicate.

pecificati software manufacturers to create ts that wil nments. The specifications

we would not have as oftware o ause each product would have to

, etc.

ou memorize the layers, you do need to remember the which each layer is respo

layer thThe OS

s the task, it is thimply defines whi

which with di

are to be used at eacpes of hardware and software ca

These s ons make it possible for hardware andproducdescribe how com

l function in different computing enviroponents are supposed to function. Without them

many sbe specialized towards each type of

r hardware packages available to us, bec computer or operating system



Devices and the OSI Model As a networking professional, you will usually be working in the first three layers of the OSI model: The Physical layer, Data Link layer and the Network layer. These are the layers that have the most to do with hardware devices and other components that you can change. Programmers usually deal with the upper layers and decide what protocols, etc. are going to be used when they write a program.

Repeaters, bridges, routers, and gateways are the most common devices that are used to expand a network. The networking professional needs to be familiar with these devices, as well as where in the OSI model they operate.

Repeaters

A repeater operates at the Physical layer of the OSI model. It regenerates or amplifies a signal across LANs. As electrical signals travel across a network medium the signal weakens as a result of resistance from the cabling itself. This weakening is known as attenuation. A repeater amplifies these signals so that they can travel further or across

A bridge operates at the Data Link layer of the OSI model. Bridges connect two separate networks to form one logical network. They rely on MAC addressing to forward messages to their destination.

Routers

Routers operate at the Network layer of the OSI model. Routers are responsible for using logical addresses to move packets from one network to another and deliver them to a host. Most routers today support multiple protocols such as:

TCP/IP SNAP

LANs.

Bridges

SNA PPP

SLIP PPTP

X.25 XNS Protocols

IPX/SPX DECnet

The following is a list of NON-ROUTABLE protocols:

• NetBEUI

• DLC

• LAT



Each router has its own table that defines all routes connected to it. Router tables can be ey can be dynamically updated using

er es as a gateway and allows for communication between

popular example is an SNA Gateway, which can be

entered manually by a network administrator or throuting protocols such as RIP and OSPF.

Brouters

A brouter operates at both the Data Link and Network layers of the OSI model. It is a device that combines the functions of the bridge and router. If a routable packet is received the brouter will route it using a routing table (make intelligent decisions of how best to route the data). However, if a packet is received from a computer using a non-routable protocol such as NetBEUI, the brouter will bridge the packet based on its MAC addressing.

Gateways

Gateways operate in the upper layers of the OSI model (from the Transport to Application layers, but usually in the Application layer). A gateway connects two computer networks that use different protocols or even different technologies. The gateway translates between the two networks so that they may communicate. A computwith special software servcompletely dissimilar networks. Aused to connect an IBM mainframe computer to a Microsoft network.



s, Inc. (IEEE) formed a his project is known as the 802 project (named

you need

IEEE 802 Standards In 1980 the Institute for Electrical and Electronic Engineercommittee to create standards for LANs. Tfor the year and month the project started, February 1980). These standards were prepared before the OSI standards, but the two sets of standards were designed to be compatible. The following table lists the 802 standards by category: (The ones to know are the ones in bold!)

Number Defines

802.1 Internetworking

802.2 Logical Link Control (LLC)

802.3 Carrier Sense with Multiple Access and Collision Detection (CSMA/CD)

802.4 Token Bus LAN

802.5 Token Ring LAN

802.6 Metropolitan Area Network (MAN)

802.7 Broadband Technical Advisory Group

802.8 Fiber Optic Technical Advisory Group

802.9 Integrated Voice/Data Networks

802.10 Network Security

802.11 Wireless Networks

802.12 Demand Priority Access LAN, 100BaseVG AnyLAN

If you would like more information on these standards, visit IEEE’s web-site at http://www.standards.ieee.org

There are also many other web sites that discuss these standards, and if you would like more information on them, a little surfing might be in order.





etwork Drivers and the OSI Model

hence, at the Media Access Control (MAC) sub-layer of

developed to ese standards is to

s

ND om Corp. and it defines the interface a rt

mu ace provides a boundary between a protocol river, which allows any NDIS-compatible protocol stack to function with any

-developed by Novell and Apple and serves the same purpose as NDIS, but is S and

NJust like every other device in a computer, the NIC also needs a device driver to function. The driver allows communication between the operating system and the NIC, and the network. The NIC driver operatesthe Data Link layer of the OSI model. Two sets of standards have beendefine the interfaces between the NIC and the driver. The purpose of thallow operating system vendors (such as Microsoft and Novell) to write multiple driverfor the same NIC. This way more than one protocol stack can be bound to a single NIC.

NDIS (Network Driver Interface Specification)

IS was co-developed by Microsoft and 3Cbetween the Data Link layer NIC driver and the network transport protocol. It defines way to bind more than one protocol to a single driver, which will allow a NIC to suppo

ltiple protocols. This vendor-neutral interfand the dNDIS-compatible driver.

ODI (Open Data Link Interface)

ODI was codesigned for use with Novell NetWare and Macintosh environments. However, NDIODI are incompatible with one another.

and OSI Protocols Protocols are the rules thatused to com u is because of t

govern communication between computers. The protocols m nicate in a network environment are called protocol suites or stacks. This

he way they work within the OSI layers (on top of one another). Network



protocols are rThey also hand

Network protocols work at various layers of the OSI model. It is the protocol operating at a certain O support for appTransport laye rs of the OSI model and are responsible r or free, and in full. dle the addressing and otocols

must be bound to the NIC. This binding process is what river. It is possible to bind two protocols to one NIC

nicates with another entirely dissimilar network.) ound to the NIC determines which one the

l

y be connection-oriented or connectionless.

ine. You have no confirmation (unless he calls you back)

unicate. The receiving computer acknowledges that it as sent. This form of communication protocol guarantees the

ssage was delivered. Connectionless communication is

messages across ble. Protocols that are unable to send messages across

esponsible for addressing and routing communication over a network. le error checking and acknowledgments of transmitted data.

SI layer that defines that layer’s function. Application layer protocols providelication-to-application functions in the upper layers of the OSI Model.

r protocols reside in the middle laye fo establishing sessions and ensuring that data is sent and received err Network protocols reside in the lower layers of the OSI model and han

routing functions of network communication. The network layer pralso are responsible for error checking (CRC) functions.

Protocol Binding

In order to function, a protocol links the protocol stacks to the NIC d(such as TCP/IP and IPX/SPX) or to have two NICs with one protocol bound to each one. (This is useful if your network commuThe order in which these protocols are bnetwork operating system will attempt to use first. For example, if TCP/IP is bound first, the operating system will attempt to communicate using TCP/IP first. If that fails, it wilthen attempt to communicate with the second protocol.

Connection-Oriented vs. Connectionless

Communication between computers maConnection-oriented would be like dialing up your friend to ask them to come to a party. You speak directly to your friend who either agrees or disagrees to come. In a connectionless scenario, it would be like calling your friend and simply leaving a message on his answering machthat he received the message.

In connection-oriented communication, the sending and receiving computers actually establish a connection to commreceived the data that wdelivery of data.

In a connectionless communication, the data is simply sent and assumed to be received. There is no guarantee that the mefaster, but connection-oriented is more reliable.

Routable vs. Non-Routable Protocols

In the early days of networking, LANs were usually just one network that served a singlecompany or department. In today’s LANs however, it is not uncommon for more than one LAN to be connected using a router. Protocols that are able to route these devices are called Routarouters are called Non-Routable.



order) of some routable protocols:

/ SPX

OUTABLE protocols:

s

cols and Stacks

etworking protocol stacks. As a networking

The following is a list (in alphabetical

• AppleTalk

• DECnet

• IPX

• PPP

• PPTP

• SLIP

• SMB

• SNA

• TCP/IP

• UDP

• X.25

• XNS Protocols

The following is a list of NON-R

• DLC

• LAT

• NetBEUI

Non-routable protocols cannot be used in routed environments (such as the Internet). It iimportant that the networking professional know the difference between routable and non-routable protocols and which protocols are routable.

Networking Proto

The following are common routable nprofessional, you should be familiar with these protocol stacks and you should know theOSI layer in which their components function.



• AppleShare – Provides Application layer services for Macintosh.

o computers at the Transport layer.

e

ss a router SPX is used.)

k Interface Driver) – Resides in the Data Link layer in b-layer. This is the NIC driver in the IPX/SPX suite.

a destination. It chooses the route yer.

P (NetWare Link Services Protocol) – This Network layer protocol is rotocol. In addition to hop count, this protocol takes into

rotocol resides at four different layers of the OSI model, and handles file and print services. At the Application layer it handles application interfaces. At the Presentation

AppleTalk

This proprietary protocol stack allows Macintosh systems to operate in a network environment. This stack consists of:

• AppleTalk Filing Protocol (AFP) – Manages file sharing at the Application layer

• AppleTalk Transaction Protocol (ATP) – Provides connection between tw

• Datagram Delivery Protocol (DDP) – Provides transmission of packets across anetwork. It resides in the Network layer.

DECnet

This is Digital Equipment Corporation’s protocol stack. It is a routable protocol that can also use TCP/IP and OSI protocols.

IPX/ SPX

This protocol is the proprietary protocol that was developed by Novell for Netware servers and clients. It has been modified over the years and now contains the following components:

• IPX (Internetwork Packet Exchange) – Works on the Network layer of thOSI model and provides connectionless service. It uses the MAC addressand is non-routable. (If data must cro

• SPX (Sequenced Packet Exchange) – Is a Transport layer protocol and is a connection-oriented protocol. It is a routable protocol.

• MLID (Multiple Linthe MAC su

• LSL (Link Support Layer) – Also resides at the Data Link layer and provides the interface between the MLID and the upper layers.

• RIP (Routing Information Protocol) – This is a simple routing protocol that counts the hops needed to reachwith the fewest hops, regardless of speed. It resides in the Network la

• NLSalso a routing pconsideration link speed and network traffic to make more efficient routing decisions than RIP.

• NCP (NetWare Control Protocol) – This control p



At the Session layer it establishes and

rvers to broadcast (at specified intervals) the location and services

that are available from that server.

• NWLink – This Transport layer protocol is Microsoft’s version of IPX/SPX. It is routable and provides support for NetBIOS names.

Many companies use Netware with the TCP/IP protocol stack. Novell Netware 5.1 and

layer it handles data translation. controls sessions. At the Transport layer it handles sequencing, flow control, and connection-oriented error control services.

• SAP (Service Access Protocol) – This Application layer protocol is usedon se

later installs TCP/IP by default.

SMB (Server Message Block)

This Microsoft protocol operates at the Presentation layer and is used for communication between the server and the redirector.

SNA (Systems Network Architecture)

This protocol suite is used with IBM mainframes and AS/400 systems. The two main protocols in this stack are APPC (Advanced Peer-to-Peer Communications) and APPN (Advanced Peer-to-Peer Networking). APPC supports Transport and Session layer services, while APPN provides Network and Transport layer connections.

TCP (Transmission Control Protocol)

The TCP/IP suite contains two major protocols, TCP and IP. It also contains several others that the networking professional needs to be familiar with. We will cover TCP/IP extensively in Chapters 8 & 9.

TCP functions at the Transport layer of the OSI model and is a connection-oriented protocol. TCP is responsible for adding header information that contains error checking and flow control information.

IP (Internet Protocol)

IP is a connectionless protocol. It operates at the Network layer of the OSI model and is responsible for addressing packets and routing them over the network.

UDP (User Datagram Protocol)

UDP provides the datagram service in TCP/IP. A datagram is a kind of packet that has minimum overhead. No error checking exists and delivery is not guaranteed, so the application must do the error checking and retransmission if necessary. Missing packets and out-of-sequence data is not checked and no acknowledgements are sent. It is faster than TCP because it is connectionless. It is also layered on IP like TCP.

FTP (File Transfer Protocol)

This protocol is used for file sharing between computers on a TCP/IP network. FTP is an Application layer protocol and is available for nearly every operating system. It is used to upload and download files on the Internet and between two computers.



le Transfer Protocol)

kly and more l (FTP). It is less capable than FTP because it uses

s,

l allows a user to log on and run applications remotely. t can

t is responsible for sending E-mail from the

e ewest hops,

eed. It resides in the Network layer.

niversal Time (UTC) to synchronize

ol. OSPF counts the number of hops to the dition, it also takes into consideration the network speed

ving IP addresses to MAC addresses. ARP keeps a table of that have been resolved in the previous 10 minutes.

ddress. ARP will add the information to its table for

TFTP (Trivial Fi

Trivial File Transfer Protocol (TFTP) is used for transferring files quicsimply than the File Transfer ProtocoUDP rather than TCP, making it connectionless. If you do not need to use passwordthen TFTP would be advisable over FTP.

Telnet

This Application layer protocoThe local computer acts as a display only and all processing occurs remotely. Telnealso be used for remote configuration of servers and network devices such as routers and switches.

NFS (Network File System)

Sun Microsystems developed NFS as a file and drive sharing system. It operates like a combination of Telnet and FTP and allows users to access files and drives on remote computers as if they were local resources. It is an Application layer protocol.

SMTP (Simple Mail Transfer Protocol)

SMTP is an Application layer protocol thasender’s server to the recipient’s E-mail server.

RIP (Routing Information Protocol)

RIP (Routing Information Protocol) – This is a simple routing protocol that counts thhops that will be needed to reach a destination. It chooses the route with the fwithout regard to sp

NTP (Network Time Protocol)

Network Time Protocol (NTP) is used in a networked environment to synchronize computer clock times. It uses Coordinated Ucomputer clock times to a millisecond. It is designed to be reliable and allows for scalability.

OSPF (Open Shortest Path First)

Like RIP, this is also a Network layer protocdestination computer, but in adand traffic and makes routing decisions based on the best route, instead of only the number of hops.

ARP (Address Resolution Protocol)

ARP is responsible for resolcorresponding IP and MAC addresses ARP will first check its table and if a matching address is not found, it will broadcast on the local subnet to determine the MAC address of the computer with the associated IPaddress. The computer that has the corresponding IP address will respond to the broadcast by sending its MAC afuture use. RARP (Reverse Address Resolution Protocol) is a related protocol that performs the same function, but in reverse.



ing protocol that is sometimes referred to as a public data network

ard telephone lines and switches, which can be unreliable due to the quality of phone lines.

In addition, X.25 is also an equipment specification. The first specification refers to the DTE (Data Terminal Equipment). This is the host on an X.25 network. The second part of the specification is the DCE (Data Communications Equipment). The DTE acts as an endpoint for communications and the DCE acts as an entry point for the DTEs.

This is an older packet switching network that uses switches and circuits. Data is routed via the best connection at a given time. This means that routes change as conditions change. Packets from the same transmission are routed via the best route (and don’t necessarily follow the same route) and are reassembled at the receiving end. At each stop, packets are re-examined to determine whether they are damaged, making X.25 a very slow but very reliable protocol. Because of this, the X.25 network is sometimes referred to as a cloud. Data goes in and comes out, but in between, it is out of the administrator’s control.

X.25 functions take place at the Physical and Network layers and normally interface with a protocol called LAPB (Link Access Procedures-Balanced).

XNS (Xerox Network System)

XNS is a proprietary protocol developed by Xerox for their Ethernet LANs. It is bulky and slow and has largely been replaced by TCP/IP.

Non-Routable Protocols

The following protocols are non-routable. This means that they may not be used with networks that use routers to connect multiple LANs. This also means that they may not be used to connect to the Internet.

DLC (Data Link Control)

DLC operates at the Data Link layer of the OSI model. It was originally used to connect IBM mainframes to HP network printers. This protocol is not used for data communication. Instead, it is installed only on the print server and communicates directly with the printer.

This is not an actual protocol and is not used to perform networking functions, only printing functions.

LAT (Local Area Transport)

LAT does not have a Network layer, which is the main reason that it is non-routable. It is a DEC protocol used for interactive, asynchronous terminal traffic over a LAN. It is typically used between a DECserver and a VAX minicomputer.

X.25

X.25 is a packet switch(PDN) because it is sometimes used by more than one organization. This is really a type of network that is owned by telephone companies who charge organizations for use. It uses stand



NetBEUI (NetBIOS Extended User Interface)

ble protocol works at the Transport layer of the OSI model. It is fast, easy

This non-routato configure and small, which is an advantage if using older MS-DOS-based systems. Itmay be used with bridges, but is primarily used today for backward compatibility with existing networks.



Other Protocols

ls with which you should be familiar:

SLI CP/IP connectionsNetBEUI, or DHCP. SLIP requires static encryption. SLIP is not used as mu as PPP.

PPP (Point-to-Point Protocol)

This protocol was developed to replace the SLIP protocol and alleviate some of its limitations. PPP supports IPX, NetBEUI, DHCP, and other protocols as well as TCP/IP. It also supports data encryption.

PPTP (Point-to-Point Tunneling Protocol)

This is an extension to the PPP protocol. The main improvement is that it allows clients to connect remotely over the Internet. PPTP encapsulates TCP/IP, NWLink and NetBEUI, enabling it to use the Internet as a backbone for NWLink and NetBEUI. Users can establish secure encrypted access to their corporate networks via Virtual Private Networks (VPNs) that PPTP establishes.

SNM anagem

Devices using TCP/IP use SNMP for controlling network communications. This management protocol interfaces with network analyzer software making it easier to manage complex networks. SNMP is used extensively with intelligent hubs.

ISO

This is a complete standard with each layer having a protocol (or protocols) mapped directly to it. It provides full networking functions at every layer of the OSI model.

ICM rol Message Protocol)

ICMP is used in error-handling and control procedures. It operates at the Network layer of the OSI model and performs connection services and flow control services. Like a traffic report on your radio, it detects congested areas and links that are down, and notifies upper layers to route around them.

DN Name System)

DN hat humans understand into names that the computer understands. It m and provide hostname to IP address resolution. This database is typically dynamic in today’s modern networks, but it can also be modified manually by the network administrator.

XDR (External Data Representation)

XDR handles translation and operates at the Presentation layer. It provides machine-inde slations that m y include encryption and data descriptions.

PC (Remote Procedure Call)

RPC operates at the Session layer of the OSI model. It handles session establishment, administration, file transfers, and connection release. RPC is used by the redirector to

The following are other protoco

SLIP (Serial Line Internet Protocol)

P supports T made over serial lines. It does not support IPX, IP addressing and doesn’t support data

ch

P (Simple Network M ent Protocol)

/OSI Standard

P (Internet Cont

S (Domain

S translates names taintains a database s

pendent data tran a

R



determine if a resource is local or on the network. It makes the remote resources appear

otocol that we will be covering it in depth later in

local to the computer.

Note: TCP/IP is such an important prthe text.



Summary In this chapter, we learned about the OSI model and its importance in networking. We

thes ct with each other.

It is important to note that memorizing the OSI model will not only help you pass the test,

For example, if you can get to the server through a router, you know that networking is taking place and that you have functionality up to layer three.

he networking professional.

also learned what type of devices function at various levels of the OSI model and how e devices intera

but also help you to narrow down problems when troubleshooting a network.

The OSI model is an invaluable tool to t




Keyword Definition

802.x Standards

Application Layer

Bridge

Brouter

Data Link Layer

Gateway

LLC (Logical Link Control)

MAC (Media Access Control)

Network Layer

Non-Routable Protocol

OSI

Physical Layer

Presentation Layer

Protocol Stack

Repeater

Routable Protocol

Router

Session Layer

Transport Layer



1. Who developed the OSI model?

rates at the _____ layer of the OSI Model.

4. A bridge operates at the _____ er

5. A router operates at the _________layer of the OSI model.

6. Data com kes plac _________ r of the OSI.

7. Which OSI layer is responsible for the MAC add

. What is the function of the Application Layer?

of

the Presentation Layer?

12. What is a MAC address?

13. Which part of this MAC address is the Device ID? 00-01-A5-D3-B4-01

Review Questions – Chapter 3

2. Name the seven layers of the OSI model.

3. A network adapter card ope

___ lay of the OSI model.

pression ta e at the _ laye

ress?

8

9. The ____________ layer is responsible for the mechanical and electrical functionstransmitting data over a network.

10. What is the function of

11. Which OSI layer is responsible for establishing, managing, and ending connections?



kes routing decisions?

uence, without duplication

17. What is the function of a Gateway?

standard defines the Logical Link Control (LLC) sub-layer?

19. What are NDIS and ODI?

20. Describe protocol binding.

21. Which is faster, connection-oriented communication or connectionless communication?

ny routable protocols as you can remember.

o segments and are using an

14. Which OSI layer ma

15. Which OSI layer is responsible for delivering data in seqand error free?

16. The Data Link layer has been split into two sub-layers. What are they?

18. Which IEEE

22. Name as ma

23. You have expanded your NetBEUI network into twintelligent router to optimize network traffic. Will this work? Why or Why not?

Chapter 4 – Hardware Media and Peripherals


Chapter 4 - Hardware Media and Peripherals This ch ter explores d the hardware aspect of network operations. There a several cab we will address here, along with connectors, networ dapter card er hardware and per

The effect of hardware on network performance wi g operation. Understanding how different network topologies interact with different types of cable is essential. How to properly configure and use network adapter cards, and how wireles ong the topics we will cover in this chapter.

Network Cabling Although wireless networks do exist, (and we’ll cover them later in this chapter), most networks utilize som le to carry transm

here are numerous kinds of cable, but fortunately for the networking professional there are only three major types that you need to understand.

al Cable

e called the ground as well as an outer cover. Because it is shielded, it is less susceptible to EMI than UTP.

Coaxial cable is used in Ethernet Networks; 10Base2 (Thinnet) and 10Base5 (Thicknet)

Thinnet is about ¼-inch thick and is flexible and easy to install. It has a maximum segment length of 185 meters (about 606 feet) and a transmission speed of 10 Mbps. It uses a BNC (British Naval Connector) “T” connector to connect directly to the NIC. It is not often used in today’s networks, but may still be used in some temporary installations such as a construction trailer (although wireless would be a much more likely alternative).

Thicknet

Thicknet is about ½-inch thick and f er core is thicker than Thinnet and can carry signals farther (maximum segment length is 500 meters or about 1650 feet). It

nsmission speed of 10 Mbps. It uses a device called a transceiver to connect . The drop cable is connected to the NIC’s

which is more commonly known as a DB-15 connector.

apre

network media, anling options, which

k a s, and oth ipherals.

ll be key to your networkin

s networks function are am

e type of cab issions on the network.

T

Coaxi

Coaxial cable consists of a copper core (either solid or stranded) surrounded by plastic foam insulation, a braided metallic shi ld

in a Bus topology.

It can transmit voice, video, and data over longer distances that UTP or STP.

Thinnet

airly rigid. Its copp

also has a trathe Thicknet cable to the NIC via a drop cableAUI (Attachment Unit Interface) port connector, or DIX (Digital, Intel, Xerox),



an Thinnet, it is not as easy to install. In the past, Thicknet was

Because it is thicker thused as a backbone to connect several Thinnet networks. In today’s networks, it has been replaced by twisted-pair cable and fiber optic cable.

Summary of Coaxial Cables

Not all coaxial cables are the same. They are specified based on their impedance. Impedance is a unit of measurement for resistance to AC voltages. It is expressed in ohms. In order for the network to operate at peak performance, all electronic componentsmust operate at the same impedance. Using the wrong cable will cause poor performanceand/or failure of the network.

Uses Type Impedance – Ohms

10Base5 Thicknet

RG-8 50

10Base5 net

RG-11 50 Thick

10Base2 Thinnet

RG-58 50

Cable TV RG-59 75

ARCnet RG-62 93

Coaxial Connectors

British Naval Connectors (BNC) are used in both Thinnet and Thicknet networks toconnect the cable to the computers. As a networking professional you will need to be familiar with the different types and their uses, as well as ho

w they are attached to the cables.

BNC Cable Connectors

BNC T Connector

The BNC T connector is used to connect the network interface card to the cable. It is attached directly to the NIC but allows network signal to flow straight through it as well as to the NIC.



BNC Barrel Connector

is

tor

The BNC barrel connector is used to connect two lengths of Thinnet cable together. Itsoldered or crimped onto the cable to make the connection.

BNC Termina

Both ends of the cable must be terminated to absorb signals and eliminate signal bounce. The BNC terminator is a connector that has a resistor built in that performs this function. One of the terminators must be grounded.

BNC Connectors

N Connectors

Thicknet uses N connectors that screw on. Both ends of the cable need to be terminated with one end grounded.

N Connector

Transceivers

The computers in a Thicknet network do not connect directly to the cable as with Thinnet. Thicknet uses a device called a transceiver. A transceiver is a device that transmits and receives signals on a network medium.

The transceiver has a port for an AUI connector (AUI port connectors are also called DIX connectors or DB-15 connectors), and an AUI cable. This cable is called a drop cable or a transceiver cable, and is used to connect the device to the network. It is common to connect a Thinnet LAN to a Thicknet backbone using a transceiver.



Transc

s

eiv

Vampire Tap

Although transceivers can be connected by cutting a cable and splicing N connectors and T conne rs o ver, this was time-consuming and it absorbed signal so it was not the common approach. Instead, most networking professionals used a clamp-on transcei . Th re of o as vampire taps because they utilized sh punctured the cable to make the connection. This types of connections have been largely replaced by newer cable methods such as twisted-pair and fiber op cab

er

cto n the transcei

ver ese clamp-on transceivers wearp teeth that

ten referred t

tic le.

Vampire Tap

Twisted-Pair Cable

Twisted-pair cable has become the most popular type of cable used in networks today. It is flexible and easy to install and is the least expensive of all the cable types.

This cable type consists of insulated pair strands of copper wire that are twisted around one another. There are four pair strands in most twisted-pair cables. The twist helps



sensitivity to EMI. There are two types of twisted-pair cables: telephone wire we

UTP

Unshielded Twisted-Pair (UTP) cabling is the less expensive of th d-pair cable types and hence the m ular. Since it i nshielded, i re sensitive to EMI. It has a m mum segment length of 100 metenum twists per each pair o The tighte twist, the fassignal can be sent through the wires without crosstalk. Currently, there are six categories. Category 3 cabling has a transmission spe 10 Mbps. C ry 5 UTP hastr speed of up to 100 Mbps. UTP wire typically consists of eight wires or four pairs. The following is a summary of UTP cables.

prevent crosstalk and Unshielded Twisted-Pair (UTP) and Shielded Twisted-Pair (STP). The have all seen in our homes is an example of twisted-pair cabling.

e twisteost pop s u

rs. The quality of UTP is based on the t is mo

axiber of meter in f wires. r the ter the

ed of atego a ansmission

Category M um Data Rateaxim Uses

1 Less than 1 Mbps Doorbell Wiring

2 4 Mbps Token Ring and Voice

3 16 Mbps 10BaseT and Token Ring

4 20 Mbps Token Ring

5 100 Mbps ATM and Gigabit Ethernet

5e 1000 Mbps ATM and Gigabit Ethernet

6 1000 Mbps Extremely fast broadband

STP

Shielded Twisted-Pair (STP) cabling is insulated with a foil mesh between the wire pairs. This results in less sensitivity to

EMI.

Twisted Pair Cabling



Twisted-Pair Connectors

ally connected with RJ-45 connectors. An RJ-45 connector looks

5 jack has eight.

UTP and STP are usujust like a common telephone jack (RJ-11) only larger. An RJ-11 jack has four connection points where an RJ-4

RJ-45 Connector

App T

AppleTalk networks utilizing STP cabling uses a DIN-type (DB-9) connector.

Dis

Distrib te more room for cables when ium. This is an excellent way to organize network cables.

nels (sometimes called punch down blocks) are also used with UTP installations. They comof u toand org k of the patch panel in what is called the pinusin ainsulatiRJ-45 ports (a port is a female counterpart for the RJ-45 jack). The RJ-45 jack’s position can e for flexibil re typicall themselves.

le alk

tribution Panels

ution racks and shelves are sometimes used to creafloor space is at a premExpandable patch pa

e in various sizes up to 96 ports and support transmission speeds p 10 Gbps . These patch panels act like a switchboard where cables are connected

anized. The wire is assembled in the bac location. The pin location is a color-coded slot into which the wire is punched down g special tool punch down tool to make the proper connection by stripping the

on from the wire without breaking the wire. The front of the patch panel contains

th refore be changed from patch panel to patch panel to use a different set of cablesthe same connection. This gives the network administrator a greater degree of

ity and provides fault tolerance for the network cabling system. Wall plates ay used to make the connection to the computers

Wall Plates for RJ-45



s it is the most expensive and most difficult to install of all the cabling types, it is therefore not as common as UTP. .

Fiber-optic cable consists of a glass core surrounded by a coating of cladding (layer of glass or plastic). This cladding reflects the signal back into the fiber, which reduces signal loss. (The core can also be made up of plastic, which is easier to install, but plastic core fiber-optic cannot carry the signals as far as glass.)

Because data only passes in one direction over fiber-optic cable, it consists of two separate strands enclosed in a plastic jacket for strength. One strand transmits and one receives. Signals are sent along the cable as pulses of light.

Fiber-Optic Cable

Fiber-optic cable is the ideal cabling for networking. It supports extremely high bandwidths and is not subject to EMI.. It also supports much longer segment lengths (several miles). However, a

SC Connector (for Fiber Optic Cable)

ST Connector (for Fiber Optic Cable)

Because data is transmitted as light and not as electrical impulses, the data cannot be

ed with standard UTP. IBM cabling is based on its Type. The following is a summary of IBM Types:

tapped or stolen. Because of this feature, fiber-optic is used in networks that need a secure media that transmits at high speeds over long distances.

IBM Cabling

IBM has its own special cabling for use on their Token Ring networks. They do not conform to the same specification as us



Type Wire Specs Uses

1 Two STP solid core 22 AWG wires – maximum length 101 meters (331 feet).

distribution boxes or between different wiri

Connect between terminals and

ng closets.

2 Six twisted pairs, two STP and four UTP – maximum len

Same as type 1 but adds voice gth capability along with data.

100 meters (328 feet).

3 Four UTP with two twists per inch – 22 or 24 AWG wire –

Lower cost alternative to type 1 or

maximum cable length is 45 meters (148 feet).

2. Cannot be used for 16 Mbps Token Ring.

4 Not Defined

5 Two 62.5/125-micron multi-mode fibers.

Fiber Optic

6 Two STP – 26 AWG Wire Data patch cables.

7 Not Defined

8 Two STP – 26 AWG Wire Contains a shield for use under carpets.

9 Two STP –26 AWG Wire Plenum grade.

IBM has developed its own cabling complete with its own standards and specifications. The connector that they developed is unique in that any connector can connect to another as opposed to having “male” and “female” connectors as with other types of connectors. An IBM connector is sometimes called a hermaphrodite. These are very rarely used in today’s modern networks.

IBM Connector



Summary of Cabling

ations for network media: The following table summarizes the specific

Media Bandwidth (Mbps) Nodes/ Segment

Maximum Nodes

per Network

Maximum Cable Length

(meters)

UTP 4-100 1 1024 100

STP 16-155 Varies 260 100

Coaxial Thicknet

10 100 300 500

Coaxial Thinnet

10 30 90 185

Fiber Optic

2000 1 1024 2000

Infrared 1-10 NA Varies 32

Note: We will discuss Infrared later in this chapter.



erican Wire Gauge)

re.

ge.

is bi-

TDM (Frequency Division ignal flow is uni-directional.

ive nd a message.

d and receive) but only one at

eous transmissions. For example, the oth you and the party you are

.

Plenum

A p u ng and the floor above. This space is used to circulate air through a building. Because this space does circulate air through a building,

is less expensive than Plenum grade cable but it gives off poisonous smoke and gas pe of cable were used in the plenum, these fumes would circulate

Cabling Terms The following are terms that you will encounter when working with network cabling:

AWG (Am

AWG is the standard that describes wire thickness. As the AWG wire number decreases,the wire thickness increases. For example, 10-gauge wire is heavier than 14-gauge wiTypical STP and UTP wires are 24-gau

Bandwidth

Bandwidth is a term used to measure the ability of a network medium to transmit data.Bandwidth is measured in megabits per seconds (Mbps) or gigabits per second (Gbps).Baseband vs. Broadband

There are two techniques that are used to transmit signals over cable:

• Baseband uses the entire capacity of the cable as a single channel. It is used with digital and utilizes TDM (Time Division Multiplexing). The signal flow directional.

• Broadband allows two or more channels to share the bandwidth of the cable or medium. It is used with analog and utilizes Multiplexing). The s

Simplex vs. Duplex

• Simplex refers to one-way communication only. For example, a pager can recea message, but cannot se

• Half-Duplex can send transmissions both ways, (sena time. An example would be a CB radio transmission where only one person can talk at a time.

• Full-Duplex allows for two-way simultantelephone utilizes full-duplex transmissions. Btalking to can talk and listen at the same time

Grade Cabling

len m is the space between the ceili

fire codes are very specific about what types of cabling can be run in this space.

Coaxial cable comes in two grades: Polyvinyl Chloride (PVC) and Plenum. PVC is usedfor the outer cover and the insulation in Polyvinyl Chloride grade cabling. PVC grade cable when burned. If this tythroughout a building in the event of a fire.



al must be aware of local fire codes regarding plenum cabling.

In contrast, Plenum grade cable is insulated and jacketed in special materials that give off a minimum amount of smoke and fumes. It is therefore specifically designed to be used in these circulation areas. A networking profession

Plenum Grade Cables

m

ere are tight corners, the flexibility of the medium should

le need to be purchased? (If installing cabling in the plenum, local d to be addressed.)

e

Selecting Cables

As a networking professional you will need to determine which kind of cabling mediuto use for a given network. There are many factors that you must consider if you are to meet your networking objectives, such as:

• Budget

• Network Traffic

• Security Needs

• Size/Distance

• Environment

The installation parameters need to be considered as well. For example, how will the cable need to be installed? (If thbe considered.)

Will plenum grade cabfire codes will nee

Will the cable be installed in “noisy” areas where EMI will be a factor? (If installing thecable near equipment or fluorescent lighting, shielded cable or fiber optic cable might bmore appropriate.)



the cable runs need to be? (If the network will be small, there is no need to

If security is an issue on the network and the data to be transmitted needs to be secure, might be appropriate to avoid any tapping.

eeds and, last but not least, cost are issues that will need to be addressed n’t

How long willuse heavy duty cabling when another type would be more cost-effective. On the other hand, attenuation could have an affect on network performance if you use cabling on a large network where long cable runs are a factor.)

fiber-optic cabling

Is future growth of the network expected? (Expandability for future growth is easier to achieve if it is planned for in advance.)

Transmission spwhen planning your network. Building a low-cost network that doesn’t do the job wowin you any brownie points in the long run!



s (NICs)

e the r can understand into signals that can be transmitted over the d of course to translate it back again.)

nd the

rs carry data internally via data pathways called buses. Because these paths are ide, data is moved along in groups. This is known as parallel communication.

el because the bits are traveling along side-by-side. Older computers had 8-bit buses which meant that data could be sent 8-bits at a time. Today, most buses are 16-bit r 32-bit. We’ll discuss the different data bus architectures a little later.

The NIC takes data coming from the computer in parallel form and converts it into serial data so that it can be sent along the network cable.

Signals and Clocking

In order to understand how a NIC works, you need to have a basic understanding of signals and clocking.

Signals

There are two types of signals:

Analog: Signals or waveforms that frequently take the form of sine waves, which constantly vary in one or more values. Analog data has an infinite number of possible states.

Digital: Signals that are simple 1’s (on), or 0’s (off).

Clocking

Clocking is the method used by the NIC to count and pace the number of signals that it sends and receives. Signals are sent in a continuous flow that represents the start and stop of a data frame. This is how the NIC keeps track of how much data has been sent or received.

Network Interface CardNetwork Interface Cards or NICs, are also known as Network Adapter Cards. NICs are used to connect the computer to the network. The purpose of this card is to translatdata that the computenetwork medium. (An

This card is installed into an expansion slot on every computer on the network acable is connected to the card’s port. It makes the physical connection to the network, handles network addressing, and controls the flow of data on the network.

Preparing the Data

Computeside-by-sNetwork cabling moves data in a single data stream. This is known as serial communication.

Data traveling via a computer’s bus is traveling in parall

o



Network Addressing/MAC Address

ncoding the signals it sends out on the network medium

hat is hardwired onto it by the manufacturer. The IEEE

rder to prepare data for emory Access

puter directly without having to go through the

faster than a NIC can process it. When this occurs, the data is sent to

e network to the receiving card. This

• The maximum size of the groups of data to be sent.

• The amount of data that will be sent before a confirmation.

• The time intervals between data chunks.

• The amount of time between confirmations.

• How much data each card can hold before overflow occurs.

• The speed of the transmission.

If one card is faster or more sophisticated than another card, they agree on common parameters so that the data is sent at a speed that can be handled by the slowest card. Once all of these parameters are agreed upon, the two cards start sending and receiving data.

Configurable Options

In order for the computer to communicate with the NIC, the NIC may need to be configured. Plug-and-Play cards configure themselves to be compatible with the

The NIC is also responsible for ewith its unique MAC address. This informs the other computers on the network of its location.

Each NIC has a unique address t(Institute of Electrical and Electronics Engineers) committee assigns blocks of these unique numbers to each manufacturer.

DMA (Direct Memory Channel)

The NIC must be able to communicate with the computer in otransmission on a network medium. Most computers utilize Direct M(DMA) and the computer assigns some of its memory space for use by the NIC.

DMA allows the NIC to access the comCPU. This makes transferring data much faster.

The NIC signals the computer to send the data that it wants to transmit and the computer’s bus moves the data from memory to the NIC.

Data often moves the card’s RAM (buffer) until it can be processed.

Controlling the Data Flow

Before transmitting, a NIC will send data over thcommunication takes place so that both the sending and receiving cards can agree on data flow and confirmation parameters. Before transmission actually takes place the NICs agree on the following points:



y may utilize the system’s resources. Other cards will need to e of these settings are configured by using DIP switches or

nd the NIC need to have compatible resource settings, such as:

The tCPU. T evice needs its own line. In practice, certain IRQs are almost alcon c

Typica dapter card. IRQ3 and IRQ15 may also be used if IRQ5 is already assigned. The main concept to understand is that the NIC is set up to use documeremem

PU. The device is constantly listening to this channel for commands from l

f

o

onfiguration of Direct Memory Access (DMA) channels is similar to IRQs. The main difference is that there are only eight DMA channels available. The good news is that unlike an IRQ, not all devices need one. DMA channels are used by devices that frequently need access to large amo ices can access the memory that they ne e processor. Only devices like NIC cards that need this type of memory access are assigned DMA channels.

operating system so that thebe configured manually. Somjumper settings, and some are set using software.

The operating system a

IRQ (Interrupt Request)

In errupt Request (IRQ) line is used by the NIC (and other devices) to contact the hese IRQ lines are part of the system hardware and each d

ways used for specific devices. Having an IRQ fli t (more than one device sharing an IRQ) can cause problems.

lly IRQ5 is used for the network a

an IRQ that is not already assigned to another device. Check your system’s ntation to determine its current IRQ settings. The most important thing to

ber about IRQs is that typically no two devices can use the same interrupt.

See Appendix A for common IRQ assignments.

Base I/O Port Address

This is the channel through which data flows between a computer’s hardware (like a NIC) and the Cthe processor. Each device must have a unique base I/O port number. These hexadecimaport numbers define a channel between a device and the processor. Check your system’sdocumentation for assignment and availability of base I/O port addresses.

Base Memory Address

The base memory address marks the location in a computer’s RAM of the beginning othe buffer area that is reserved for use by a device, in this case the NIC. This is sometimes referred to as the RAM start address. This buffer area is used to store incoming and outgoing data frames.

Some NICs have settings that allow you to specify the size of the buffer, while others dnot use RAM addresses at all.

See Appendix A for common address assignments.

DMA Channel

C

unts of memory. With a DMA channel, these deved without interrupting th



e NIC. The two speeds available are 4 Mbps or 16 Mbps. If the correct ring speed is not set a computer will not be able to connect to the network and may even cause the network to fail.

Connector Type

Your NIC may automatically adjust to use the kind of connector that you are using (BNC, RJ-45, or both), or you may have to configure it manually.

Wireless NICs

only used in special

Ring Speed

In Token-Ring networks the ring speed must be set on th

Wireless NICs are used to connect wireless network systems to the computer. They usually use a type of antenna (omnidirectional) and an antenna cable. Special software is usually needed to connect a wireless NIC. Wireless LANs are discussed later in this chapter.

Fiber-Optic NICs

Due to the high-cost of fiber-optic adapter cards, they are usuallycases where high-speed direct computer to fiber-optic cable connections are required.



Data Bus Architecture t

from all the devices in the computer.

: The Industry Standard Architecture (ISA) is an 16-bit bus. The Extended Industry Standard

icro Channel (MCA) is a 32 bit bus. The Peripheral bit bus, but can be a 64-bit bus. Micro Channel is a

’t

le computers. They are also called PC-Card ability enjoyed by desktop PCs, including

A data bus is a group of parallel conductors (circuit traces) found on the motherboard thais used by the CPU to send and receive data

Standard Bus Types

There are six data bus architectures found in Intel-based computers

Architecture (EISA) is a 32-bit bus. MComponent Interconnect (PCI) is a 32-data bus developed by IBM that requires licensing to be used by manufacturers and isnused much. Today most buses are either EISA or PCI.

Laptops

PCMCIA (Personal Computer Memory Card International Association) are credit cardsized expansion buses that are used in portabBuses. With this card comes the same expandnetwork connectivity. They are generally 32-bit buses.



ortant that rrectly and optimally. Most cards offer features that are designed to

:

ithout going through the CPU.

is a method by which a NIC contains RAM that it shares with actually installed in the computer.

ICs offer Bus Mastering. This is a method by which the NIC l over a computer’s bus, thereby bypassing the CPU. The data

.

are located on the NIC until it can be processed. Network traffic travels faster than most NICs can process data. Without this feature, the NIC would be a bottleneck.

Some NICs have onboard microprocessors that eliminate the need of the computer’s CPU to process data, thereby improving network performance.

Network Performance Because of the effect that the NIC can have on network performance, it is impit is configured coimprove network performance

Utilizing Direct Memory Access (DMA) improves network performance by allowing thecomputer to move data directly to the NIC’s buffer w

Shared Adapter Memory the computer as if it were

Shared System Memory is a method by which the NIC utilizes a portion of thecomputer’s memory to process data.

Both EISA and MCA Ntakes temporary controwould then move directly to system memory leaving the CPU free to process other tasksThis type of card is expensive, but investing in one can increase network performance by 20 to 70 percent.

RAM Buffering holds data in RAM chips that



Wireless Networks plies that it is a network that doesn’t use any cabling. This

rity of wireless networking. People who are constantly on the move are able to access their networks whether they are at home, the office, or on the road.

unning d not be cost effective. They are also useful to create a backup system for an

existing network. With some applications it is crucial that the network never goes down. A wireless system can help ensure that the network will still function even in the event of cable breaks.

Mobility is another reason wireless networks are created. Doctors make rounds all over the hospital and are often not at their desks when they need to access their computers. With wireless systems, a user can access the network from anywhere in the building.

Wireless is also an option for areas where installing cabling would be impossible or unsightly. This would include historical buildings where local codes would not allow renovations, or open reception areas where the cables would be visible. Outdoor installations often utilize wireless systems. Sometimes wireless systems are used to connect to remote locations such as ocean dwelling oil platforms.

Wireless networks are more portable than cabled systems, making them ideal for uses that require frequent moving.

Wireless networks use wireless access points (WAPs) to “connect” the network devices to each other. They function just like other access points (i.e. – hubs), but through the use of an infrared or radio medium.

The term wireless network imis misleading as most wireless networks utilize a system that consists of both cabling and wireless components.

Wireless networks can be classified into three basic categories:

• Local Area Networks (LANs) – There are fully wireless systems, but usually thewireless components are members of a wire-based LAN.

• Extended Local Area Networks - Wireless networks are frequently used to connect two LANs. For example, a company needs to connect two networkslocated in two nearby buildings.

• Mobile Computing - Cellular and satellite technologies are increasing the popula

Why Wireless?

Wireless networks are useful if you need to provide a temporary network where rcabling woul



Wireless Antennae

Wireless Transm

There are four basic methods of wireless transmissions:

•

•

• wave

•

You use infrared transmissions every time you use your TV’s remote control. This involves using infrared (below Red) light to carry signals to a receiver. These signals need to be rather strong because they can be affected by light sources, such as windows. The effective distance between a transmitter and a receiver is limited to about 100 feet.

Infrar io-frequ interference, and because the transmissions are tightly focused, they are also fairly immune to eavesdropping.

Infrar very fast because o its high bandwidths. Infrared networks typically broadcast at about 10 Mbps.

Infrared Networks

There are four types of infrared networks:

•

• ht Infrared

• red

•

ission Methods

Laser

Radio

Micro

Infrared

ed is not sensitive to rad ency

ed transmits f

Reflective Infrared

Line-of-Sig

Scatter Infra

Broadband Optical Telepoint



Reflective Infrared

With reflective infrared, the signal is beamed towards a central unit, which then routes the signal appropriately.

Line-

With stem, there must be a direct line-of-sight path between the transm

Scatt

Trans tes are slower with th type as the signal is designed to bounce off of walls etc. until it reaches th he effective distance of the signal is limited to about 100 feet.

Broadband Optical Telepoint

Broadband Optical Telepoint, as the name implies, uses broadband technology. Trans this high-e are competitive with cable-based systems.

Radio n

Radio less is popula with a high bandwidth at 10 Mbps. It does, howe and is subject to eavesdropping.

Narrow-Band Radio Transmission

This is som dio and is similar to broadcasting from a radio mitter and receiver are tuned into the same frequency and thus it does not require line-of-sight transmission. The signal can be blocked by heavy concrete or me it can e able mobile computing over a limited range.

Spread-Spectrum Radio Transmissions

Beca casts ver a range of frequencies, it is less susceptible to eavesdropping. This type of transmission is commonly used to connect multiple LAN segm

The signals can be broadcast via two methods: hopping, or direct sequence modulation.

In the ailable equencies are divided into hops and the transmitters and receivers “hop” from frequency to frequency for a predetermined length of tim

In the direct sequence modulation method, the message is broken into parts (called chips), which are then transmitted over separate frequencies.

of-Sight Infrared

this type of infrared syitter and receiver.

er Infrared

mission ra, ceilings,

ise receiver. T

mission speeds with nd type

Transmissio

transmission wirever, require an FCC license

r

etimes called single-frequency ra station. The trans

tal walls, but unblocked n

use spread-spectrum broad o

ents together.

hopping method, the av fr

e.



Microwave

Due to m mission capabilities, mobile computing is a growing technology that p itless range r traveling users of this type of network. There are

s of mobile computing:

• Packet-Radio Networking

• Cellular Networking

• Satellite Station Networking

Packet-Radio Networking

Packets are sent via a satellite. These network-style packets are encoded with source and destination address information, and only the destination device can receive and read the packet.

Cellular Networking

Cellular networking is achieved via the cellular phone network. The packets sent are called Cellular Digital Packet Data (CDPD) and this form provides very fast communication.

Satellite Station Networking

Microwave is currently the most common of the long distance transmission methods in the US. It is used for line-of-sight communication.

Terrestrial Microwave

This is used for earth-based communication such as between two buildings, or across large flat open areas like bodies of water or deserts. This form of microwave communication is used to transmit over shorter distances.

Satellite Microwave

This is a very expensive technology and is utilized by very large corporations who pool the billions of dollars required to develop and launch a satellite. Signals are beamed up to the satellite and then sent back down to the appropriate receiver. This form of microwave communication is used to transmit globally.

icrowave transrovides a nearly lim fo

three form





Summary The first part of this chapter covers the various aspects of network media or cables. There

isted Pair, and Fiber-Optic. Coaxial comes in two types: Thinnet and Thicknet. Twisted Pair can be Unshielded (UTP) or Shielded (STP). Fiber-Optic cable uses pulses of light to carry signals.

ed for each cable type: BNC, RJ-45, AUI, etc. In addition, you should know the maximum segment lengths for each cable type.

rk cabling we then took a look at the hardware that acts as the the computer itself. This device is called the

network interface card (NIC) and provides the physical connection to the network. It prepares, transmits, receives, and controls data flow over the network. As a network

rd for optimum per

Finally, we took a look at the future. Wireless networking is the trend of the future. As a associated with

Infrared, Laser, Radio, and Microwave.

are three primary types of cabling: Coaxial, Tw

You should know the types of connectors us

After discussing at netwointermediary between the cabling and

professional, it is important for you to be able to configure the network caformance.

networking professional, it is important to understand the conceptswireless networks. The four basic wireless types are:




Keyword Definition

Analog Signals

AWG

Bandwidth

Base I/O Port Address

Base Memory Address

Baseband

BNC Connector

Broadband

Buffer

Cellular Networking

Clocking

Coaxial Cable

Digital Signals

DMA (Direct Memory Channel)

EISA Bus

Fiber-Optic Cable

Full-Duplex

Half-Duplex

IRQ

ISA Bus

Laser Transmissions



Keyword Definition

MCA Bus

Microwave Transmissions

Narrow-Band Radio

Network Adapter Card

Network Interface Card

PCI Bus

PCMCIA Card

Plenum

Reflective Infrared

Ring Speed

RJ-11 Connector

RJ-45 Connector

Satellite Microwave

Scatter Infrared

Shielded Twisted Pair

Simplex

Single-Frequency Radio

Spread-Spectrum Radio

Terminator

Terrestrial Microwave

Thicknet

Thinnet

Transceiver

Unshielded Twisted Pair



Keyword Definition

Vampire Tap



Revie

2. What is the maximum segment length of Thicknet?

tors are used with Coaxial cable?

of UTP?

8. sion speed of category 5 cabling?

13. What is the least expensive of the cable types?

w Questions Chapter 4

1. What is the maximum segment length of Thinnet?

3. What type of connec

4. What is the purpose of a transceiver?

5. How is a vampire tap connected?

6. What is the purpose of plenum cabling?

7. What is the maximum segment length

What is the transmis

9. What is the most popular of the cable types?

10. Which twisted pair cabling is less sensitive to EMI?

11. What type of connector is used with twisted pair cable?

12. What is the most expensive cable type?



eband.

25. Which microwave transmission type is used to transmit globally?

14. List some advantages of fiber-optic cable.

15. What does AWG stand for and what is it?

16. Describe bas

17. Describe broadband.

18. What is the difference between simplex, half-duplex, and full-duplex communication?

19. What is the function of a network adapter card?

20. In Token Ring networks, what are the two ring speeds available?

21. Where would you expect to find a PCMCIA card?

22. What are some of the reasons you would need to install a wireless network?

23. What are the four basic wireless transmission types?

24. Which is the most secure type of radio wireless network?



Chapter 5 – Network Protocols & Standards


ards Chapter 5 – Network Protocols & StandIn previous chapters, we laid the groundwork for understanding networking and we looked at the different networking topologies and cabling options. This chapter explores the various protocols used in network communication. Access methods used by various network protocols will also be discussed, along with the way data is transmitted over a network in packets, or frames.

Talk

d ure, while not as popular as Ethernet, are still important technologies

fessional needs to comprehend.

A p o use to communicate with other computers, in this case, over a network. In Chapter 3, y w how each layer of the OSI Model has diff n se protocols interact is called a protocol stack.

The following m

Internet Protocol Suite TCP/IP

•

• IBM’s Systems Network Architecture, SNA

• Digital’s DECnet

•

The OSI Model was cr entioned protocols; thu h

Protocols function at three basic levels:

• Application protocols provide support for application-to-application interaction and data exchange.

• Transport protocols ensure that data is sent to the correct destination without errors.

Ethernet is one of the most popular networking architectures. In this chapter, we will discover how Ethernet works, as well as how Token-ring networks function. Appleand ARCNet networks are also included in this chapter.

After completing this chapter, you will have a working knowledge of the different network architectures and the access methods that they use. You will also understandhow networks send data and what information is included in the frames that are transmitted across the network medium. You will develop an understanding of Ethernet networks and the IEEE standards for Ethernet. You will also know how Token Ring networks function and what hardware is required to make them function. AppleTalk anARCNet architectthat the networking pro

rot col is a language that computers ou sa

ere t protocols that define how the information travels. The way the

ain protocol stacks are the most important:

•

Novell NetWare’s Protocol Suite, IPX/SPX

Apple’s AppleTalk

eated at a later date than some of the aforems, t ey do not map directly to the OSI Model.



ocols route information, handle addressing, and check for errors. Network protocols also set the standard for communicating in different network

ironments.

IPX/SPX, two protocols may be bound to one card.

der in which the operating system will use the protocol is determined by the order

ultiple computers are contending with each other for access to the network media. The rules for determining how a computer may send or receive data on

ork is called the access method.

ta

There are three primary access methods:

• CSMA/CD (Carrier-Sense Multiple Access with Collision Detection) or CSMA/CA (Carrier-Sense Multiple Access with Collision Avoidance)

• Token Passing

• Demand Priority CSMA/CD (Carrier-Sense Multiple Access with Collision Detection)

CSMA/CD is known as a contention method. This is because computers on the network compete with each other for the chance to transmit data on the cable. With CSMA/CD each computer on the network checks the network cable for traffic. If it “senses” (carrier-sense) that the cable is free, it will send data. While there is data traveling on the cable, no computer will transmit data.

Occasionally, however, two computers it data at the same time and the data will collide. The Collision Detection aspect of SMA/CD causes the two computers to stop transmitting and then attempt to retransm after a specified period of time.

Naturally, the more users who are connected to a network, the denser network traffic becomes. Greater network traffic can dramatically slow down the CSMA/CD access method.

• Network prot

env

A protocol must be bound to the network adapter card, also known as the network interface card (NIC), in order for it to be used with a network computer. In some instances, as in the case of TCP/IP or

The orin which the protocols are bound to the NIC.

Access Methods In a network, m

the netw

The access method that a system uses is designed to prevent simultaneous sending of daalong the cable. If two or more computers were to send data at the same time, the data may collide and be destroyed (or partially destroyed). The access method organizes the sending and receiving of data. All computers on the network need to utilize the same access method in order to be consistent in the way that the data is handled. This will ensure that a dominant access method being used by one computer doesn’t override access to the cable causing the network to fail.

will transm Cit



CSMA/CA (Carrier-Sense Multiple Access with Collision Avoidance)

popular as CSMA/CD because the sending computer will

to transmit will take control of a free token. It will add formation to the token as well as the data that it wishes to

around the ring until it reaches the destination computer. The destination e token and receives the data. It then adds some data to the token

ew “free” token and releases it back out on the network to be

d

priority access method is designed for the 100 Mbps Ethernet standard 100VG-AnyLAN. It has been addressed in the IEEE 802.12 standard and is based on the hubs and end-nodes being the two components that make up a 100VG-AnyLAN network. An end node in a 100VG-AnyLAN could be a computer, router, switch, or bridge.

The network traffic by searching for requests to transmit from all the nodes connected to the network. The hub is responsible for verifying that all end-nodes, addresses, and links are functioning.

Demand priority is more efficient than CSMA/CD because there is only traffic between the sending computer, hub, and destination computer, instead of broadcasts over the entire network. Because of the cabling method used with this access method, (four pairs

This access method is not astransmit its intent to transmit before sending out data. Sending out messages that it is about to transmit increases network traffic and slows down network performance. It is, however, the access method that works best with wireless connections; since the wirelesschannel can be verified before the data is sent.

Token Passing

The token passing access method is used on networks that utilize the ring topology. A token (a special type of packet) is circulated around the ring from computer to computer. If a computer needs to transmit data on the network, it must wait until it possesses the token.

A computer that is waitingadditional header and trailer intransmit. Data is transmitted in frames. The header information that is added to the token includes sending and receiving addressing information. The trailer includes error controlinformation.

When the computer is ready, the token is released back out onto the network and continues computer grabs thindicating that it received the data and releases the token back out onto the ring. The token continues around the ring until it arrives back at the source computer.

The source computer takes the token and confirms that the data it transmitted was received. It then creates a nused by any computer that needs to transmit.

If either the source (sending) or destination (receiving) computer detect errors in the datathat was transmitted, the frame would be resent. A computer in a Token Ring network must possess a token in order to transmit. Because only one computer at a time may transmit, this is not a contention method and there are no data collisions. (Some more recent versions of the Token Ring network have the capability to pass two tokens arounthe ring.)

Demand Priority

The demand

hub manages



ables quartet signaling) computers can send and receive at the

e

hub receives two transmissions simultaneously, the one with the

of wires are used, which ensame time.

Contention can occur with demand priority if two computers transmit at exactly the samtime, but it is possible to configure so that certain types of data receive priority when there is contention. If the highest priority is serviced first. If the two transmissions have the same priority level, they are serviced at the same time by alternating between the requests.



Network Communications (Frames and Packets) previously, data needs to be processed into a form that can be

puter receives the packets and

mation to each packet in mputer to reassemble them in the correct

or error checking after the data has been reassembled.

, or messages.

• d commands.

•

All packets contain

that tell the receiving computer how to reassemble the data.

As we’ve discussedtransmitted across a network medium. Data files tend to be quite large, and if they were sent out onto the network medium in this form they would overload the network cabling and slow the network dramatically. Another reason for not transmitting data in such large chunks is error detection.

Data is broken down into small chunks called frames or packets. (The terms frames and packets are often used interchangeably, but we will use the term packets.) Data is converted to packets in order for it to be moved across the network medium more quickly. Also, if there is a transmission error, only a small portion of the data is affected (and needs to be re-transmitted). The destination comreassembles them in the correct order to translate it back into the original message.

The sending computer breaks the data into packets and adds infororder to make it possible for the receiving coorder. This information allows f

Packet Structure

Packets may contain:

• Files, information

Computer control data such as service requests an

Session control codes to indicate the need of a retransmission.

:

• The source address of the sending computer.

• Instructions for the network indicating how to transmit the data.

• Instructions

• The data to be transmitted.

• The destination address of the receiving computer.

• Error checking information such as Cyclic Redundancy Check (CRC) information.



Packet Components

der contains information such as an alert signal to announce that a packet is being transmitted, the source and destination add s n.

Da

Thi a that is to be transmitted. Depending upon the network, packets can be various sizes, usually from 512 bytes to 4Kilobytes. Most files ar ill be made up to complete the transmission

Tra r

The inform depending upon the communication method or protocol used in a network. Usually, the trailer contains the error checking information.

CRC (Cyclic Redundancy Check) is a mathematical calculation that is calculated at the source com e packet. When the packets are reassembled at the des a calculation is run again. If the results are the same, the

Headers

Headers are attached to each packet. The hea

res es, and clocking informatio

ta

s p rt of the packet contains the actual data

e much larger than this so many packets w.

ile

ation in the trailer can vary

puter and attached to thtin tion computer, the

computer assumes that the packets all arrived intact. If there is a discrepancy, the CRC asks the source computer to retransmit.

A Packet





Network Standards Network standards can best be described as the physical and functional characteristic of a network. Protocols that are used with the OSI model define the rules of communication. The standards define the means of communications. For example, in a railroad, data (in this cas ious cars. There are rules or protocols that govern how the cars are loaded and the origination and destination points. However, it is the al movement of the trains (data). These provide the standards for the railroads. Not a e (some are electric, some a e are narrow gauge), but all railroads that

to

ver the physical medium. The

Ethernet (802.3)

s eter cable.

fined in the IEEE 802.3 standard and is a method for computers and data

cess

it

• 10Base5

e passengers and freight) is moved in var

rails and switches that govern the actull railroads are the sam

re diesel, some are wide gauge, and somare built to the same standards can exchange cars (data). In this section, we are going look at different standards for networks. Standards work in the Physical and Data Linklayers of the OSI model.

Logical Link Control (802.2)

The Logical Link Control layer, as addressed previously, is one of two sublayers of the Data-Link layer and is concerned with managing traffic oLLC has the ability to track acknowledgements, but its primary function is maintainingthe network link by identifying a line protocol, like NetBIOS (Windows) or NetWare (Novell).

Ethernet is a non-propriety network architecture that was originally developed at the Xerox Palo Alto Research Center (PARC) by Robert Metcalfe and David Boggs. The original version was a 2.94 Mbps network system that would connect over 100 computeron a one-kilom

Ethernet is desystems to connect over shared cabling. Ethernet uses a bus or star topology (10BaseT and 100BaseT use the star topology and 10Base2 and 10Base5 use a bus topology), and typically transmits at 10 Mbps. It is a baseband system and utilizes the CSMA/CD acmethod. It is probably the most popular network architecture used today. It can be installed with Thinnet coaxial (10Base2), Thicknet coaxial (10Base5), or Twisted Pair cable (10BaseT and 100BaseT).

There are a number of Ethernet IEEE standards. The following are the four that transmat 10 Mbps:

• 10BaseT

• 10Base2

• 10BaseFL



at it chnology (single channel). And the “T” indicates that it uses Twisted

Pair cabling. While 10BaseT can and does work with STP cabling, it is most commonly crea d

10B e f 100 meters (Twisted Pair wiring maximum segment length) and it is connected using RJ-45 connectors. If the segment must exceed this lim stances. The maximum number of nodes per network is 1024 and the minimum distance between nodes is 2.5 meters.

2

maximum number of segments containing nodes per network is 3. (There may be five may be populated.) This is referred to as the “5-4-3 Rule”. The

a transceiver. It transmits at

f eing populated. The maximum number of nodes per network 100.

10BaseFL (Fiber Optic)

n for running Ethernet over fiber-optic cable. It transmits at

ed design, to name a few.

r 100 Mbps are:

10BaseT (Twisted Pair)

The “10” in 10BaseT indicates that it transmits at 10 Mbps. The “Base” indicates thuses Baseband te

te with UTP cable.

as T has a maximum segment length o

itation, repeaters can be used for longer di

10BaseT uses the star topology.

10Base2 (Thinnet)

10Base2 uses Thinnet (coaxial) cable with BNC connectors in a Bus topology. As its name implies, it transmits at 10 Mbps using baseband technology. The “2” stands for times 100 meters, indicating its maximum segment length. The actual maximum segment length, however, is 185 meters. The maximum number of nodes per segment is 30. The

segments but only threemaximum number of nodes per network 90. The minimum distance between nodes is .5 meters.

10Base5 (Thicknet)

10Base5 uses Thicknet (coaxial) cable, BNC connectors and10 Mbps using baseband technology in a bus topology. The “5” stands for 5 times 100 meters, meaning 10Base5 has a maximum segment length of 500 meters. The maximum number of nodes per segment is 100 in a 10Base5 system, and the maximum number osegments is 5 with 3 bThe minimum distance between nodes is 2.5 meters.

10BaseFL is the specificatio10 Mbps using baseband technology. The main use for this specification is for long cableruns. The maximum segment length for 10BaseFL is 2000 meters.

100 Mbps IEEE Ethernet Standards

The IEEE committee has introduced new specifications for 100 Mbps Ethernet standardsthat can meet the demands of today’s high-bandwidth applications. These applications include video, document and image storage, and computer aid

The two Ethernet standards fo

• 100BaseVG-AnyLAN Ethernet



stands for Voice Grade. It is known by at least four names: When you see any of these terms,

The IEEE specification 802.12 is the standard that defines this technology. It is basically rnet frames and Token Ring packets. This uses a star topology

ir cable at a data transmission rate of 100 ng

100BaseVG requires its own hub and cards, and the longest cable length is 250 meters. uires special equipment.)

ethod. There are three different specifications:

100BaseT4 (this uses UTP four-pair Category 5)

aseTX (this uses UTP or STP two-pair Category 5)

eans it uses

t and per

he backbone in many larger networks.

degree, with Gigabit Ethernet, but that will be referred to later in this book. 10-Gigabit lso on the horizon.

• 100BaseX Ethernet (Fast Ethernet)

100VG-AnyLAN

In 100VG-AnyLAN the VG100VG-AnyLAN, 100BaseVG, VG, and AnyLAN. they are referring to the same thing.

a way of transmitting Etheover fiber-optic and Category 4 and 5 twisted paMbps. It can support the demand priority access method as well as an option for filteriaddress frames at the hub for added privacy.

(It can be extended longer but it req

100BaseX (“Fast Ethernet”)

Fast Ethernet (as 100BaseX is sometimes called) is simply an extension to the existing Ethernet 10Base Ethernet standard. It uses Category 5 twisted pair cable or fiber-optic cable in a Star Bus topology, using the CSMA/CD access m

100B

100BaseFX (this uses two-strand fiber-optic)

As you know, the 100 means that it transmits at 100 Mbps and the Base mbaseband technology. The T4 means that it uses four-pair twisted pair cable, the TX means it uses two-pair twisted pair cable, and the FX means fiber-optic cable is used.

Gigabit Ethernet

Gigabit Ethernet is a transmission technology based on the Ethernet frame formaprotocol used in local area networks (LANs), and provides a data rate of 1 billion bits second (one gigabit). Gigabit Ethernet is currently being used as t

Because of its intense speed, Gigabit Ethernet is carried primarily on fiber optic cable, although copper can be used with much shorter distances. ATM competes, to some

Ethernet is a



Many communication protocols are compatible with Ethernet including TCP/IP. It is also th operating systems such as:

icrosoft Windows NT Server

indows NT Workstation

• Microsoft LAN Manager

• IBM LAN Server

ll NetWare

Other Ethernet Considerations

compatible wi

• Microsoft Windows 2000

• M

• Microsoft W

• Microsoft Windows 95 and Windows 98

• Microsoft Windows for Workgroups

• AppleShare

• Nove

Ethernet networks may be segmented in order to improve performance, by joining witheither a router or a bridge. Ethernet also works in the UNIX environment.



ainframe systems.

d

How it Works

is

e and no other computer is allowed to transmit unless it possesses the token (which won’t be released until the previous computer is finished).

The computer that wants to transmit takes possession of the token. While the token is in use by a computer to send data, it is known as a data frame. The data frame is a different type of frame than the token. This is so that no other network computer will try to possess it to transmit data. The sending computer encodes the data frame with information such as:

Start Delimiter

This marks the start of the frame.

Access Control

This sets the frame priority and is also where it is encoded to let the network computers know whether the frame is a token or a data frame.

Frame Control

The information here determines whether the frame is being transmitted to all computers on the network or one specific “end station” computer.

Destination Address

This is the address of the receiving computer.

Token Ring (802.5)

The Token Ring architecture is defined in the IEEE 802.5 standard. IBM introduced Token Ring around 1984. It is not as popular as Ethernet, but is still used today, primarily in IBM mini and m

The Token Ring access method, more than the cable design, is what sets Token Ring apart. The name Token Ring implies that the physical layout is that of a ring. Actually, it is a star ring with each node connected to a central hub. The physical ring is in the hub and the logical ring represents the data’s path between the nodes.

The cable used is STP and UTP (IBM types 1, 2, and 3), and it has a transmission speeof 4 or 16 Mbps. Like Ethernet, it uses the baseband technology.

Basically, the network creates a token when the first computer comes online. The tokenactually a stream of data that allows a computer to transmit data on the cable. This token will travel around the ring until a computer signals that it needs to send data. Each computer on the network acts as a repeater and regenerates the signal as the token/data frame passes through it. A computer cannot transmit data in a Token Ring environment unless it possesses the token. Data collisions are avoided because only one computer is transmitting at a tim



ress

Cyclic Redundancy Check (CRC)

This is information for error detection.

After encoding the data frame, the sending computer releases it out onto the network where it travels around the ring until it reaches the destination address.

Note: Data travels in only one direction on a Token Ring network. Whether it travels

Source Add

This is the address of the sending computer.

Message

This is the data or file to be transmitted.

clockwise or counter-clockwise is a matter of convention. The IEEE 802.5 standards say it travels clockwise, while IBM says counter-clockwise.

The receiving computer copies the data into its buffer. It then encodes the frame with information indicating that it received the data and there were no errors detected. Or, if there were errors, it would indicate that the data needed to be retransmitted.

The frame is then released back out onto the cable where it travels back to the sending computer. Assuming that the frame acknowledges that the transmission was successful, the old frame is removed and the computer creates a new token and releases it back out onto the ring.

Beaconing

In a Token Ring environment, the first computer to come online is assigned to monitor network activity. This computer, called the active monitor, has the responsibility of making sure that frames are being sent and received accurately. The active monitor investigates any frames that have traveled the ring more than once and ensures that only one token is traveling the ring at any one time.

To accomplish this task, the active monitor performs a process known as beaconing. Every seven seconds the active monitor will send out a beacon. The beacon is passed from node to node around the ring. If a computer doesn’t receive a beacon when expected, it will notify the monitor that it didn’t receive an expected signal. This signal contains the address of its upstream neighbor, as well as its own address. The network will then attempt to diagnose and repair the problem without disrupting the entire network.

As each new computer comes online, the Token Ring network initializes it so that it may join the ring. Its address is checked to confirm that there are no duplicate addresses on the network and the other computers on the ring are notified of the new computer’s active status.



Multistation Access Unit (The Hub)

in a Token Ring network is in the hub. This hub is known by a few

of one computer will bring down the rest of the network.

eters.

g

Token Ring Connectors

r Type 1 and Type 2 cable. This is known as a hermaphroditic connector, as there are no male and

male ends. Instead the connectors can be flipped over to connect to one another. Type 3 cable is connected with RJ-45 (8-pin) connectors if using four-pair or RJ-11 (4-pin) if using two-pair. Media filters convert cable connectors between the adapter card and the telephone jack (RJ-45/RJ-11) and reduce line noise. Using the RJ connectors allows for one cable run to connect both data and telephone equipment.

Token Ring Patch Cables

IBM Type 6 cable is used for patch cables in a Token Ring network. These patch cables extend the connection between the computer and the hub or between two hubs. The Type

The actual ringnames, such as:

• MAU (Multistation Access Unit)

• MSAU (Multistation Access Unit)

• SMAU (Smart Multistation Access Unit)

A Token Ring network can be expanded to have as many as 33 hubs. Each node is connected to the hub via a cable, just as in other networks that use a hub. When a computer is connected, the internal ring converts to an external ring at each connection point.

MAUs can sense when one of the connected computers fails. The faulty node is then disconnected from the ring so as not to affect the rest of the network. In a pure token passing environment, the failure

Token Ring Cabling

STP or UTP is used to connect each node to the hub. Most Token Ring networks use IBM Type 3 UTP cabling, but types 1 and 2 may also be used. Type 1 has a maximum distance from the computer to the hub of 101 meters. Using STP, the maximum distance from the computer to the hub is 100 meters. Using UTP, it is only about 45 meters. The minimum distance using either STP or UTP is 2.5 m

There is some contention as to the maximum distance from the computer to the hub usinType 3 cable. IBM states that it is only 46 meters, but some vendors state that it is as much as 152 meters.

The maximum distance between two MAUs is 152 meters. Using STP, each ring can connect up to 260 computers. Using UTP, each ring can connect up to 72 computers.

Token Ring networks use MIC (Media Interface Connectors) connectors fo

fe



6 cable has a maximum distance of 46 meters between the computer and the hub. Type 6 e length of Type 3 cable or for connecting computers

oken Ring Fiber-Optic

Using fiber-optic cabling in a Token Ring network can increase the range up to ten times that o ken ring networ uited to fiber-optic cable.

Token Ring Repeaters

Just as in other network environm oken ring cable lengths may be increased by using repeaters. Using a pair of repeaters, hubs may be up to 730 meters apart with Type 1 or Type 2 cable and up to 365 meters apart using Type 3 cable.

Token Ring Adapter Cards

A Token Ring has two transmission speeds: 4 Mbps and 16 Mbps. The 16 Mbps card allows for a larger frame length, thereby decreasing the number of transmissions needed for data transfers. All cards on the network need to be set at the same speed. A 16 Mbps card can slow to 4 Mbps, but a 4 Mbps card cannot speed up to 16 Mbps. Therefore, care must be taken that all cards on the network are compatible.

may also be used to increase thdirectly to the hub. Patch panels are used to organize patch cables.

T

f copper. To ks are well s

ents, T

Appl

AppleTalk is the network architecture used in a Macintosh environment. Although it is not nearly as popular as the Ethernet or Token Ring architectures, it is still an environment that you may be dealing with as a networking professional.

AppleTalk is included with the Macintosh operating system software; therefore network capabilities are built into all Macintosh computers.

eTalk



AppleTalk networks are usually called LocalTalk. When a computer goes online in a LocalTalk network, the device assigns itself an address. This address is chosen at random from ilable address t will then broadcast the chosen address to determ ing the address. If it is not being used by another computer, it will store it to use each time it goes online.

Apple has always been open to third-party development. As such, AppleTalk can be used by non-Macintosh computers such as IBM compatible computers, mainframe computers, Digital Equipment Corporation’s VAX™ computers, and even some UNIX computers.

ocalTalk

LocalTalk uses STP, UTP, or Fiber-Optic cable in a Bus topology. It uses the CSMA/CD access method and can connect a maximum of 32 devices. Since Macintosh builds-in the hardware for LocalTalk in every computer, it is very inexpensive to initiate. LocalTalk performance is rather limited, so it is not used as often as Ethernet or Token Ring.

AppleShare

The file server on an AppleTalk network is called AppleShare. AppleShare also provides a print server. The client software for AppleShare is also included in the Apple operating system.

Zones

LocalTalk networks may be joined together using zones. A zone is a named Subnetwork that users may access simply by selecting it. This is useful for expanding the LocalTalk network or for relieving traffic on a larger network. AppleTalk can incorporate other types of networks such as Token Rings, by using zones.

EtherTalk

EtherTalk is simply a way to run AppleTalk on coaxial cable using an EtherTalk NB NIC. EtherTalk may be implemented on Thinnet or Thicknet coaxial cable.

TokenTalk

TokenTalk is simply a way to run AppleTalk in a Token Ring (IEEE 802.5 Standard) environment. The TokenTalk NB card is used to attach to a Token Ring network.

a range of avaine if any other computer online is us

es. I

L



ARCNet ( Attached Resource Computer Network)

In 1977 Datapoint Corporation developed the ARCNet technology. It is a simple and r Star Bus topology.

ARCNet was developed before the IEEE 802 specifications, but it can be adequately ethod

data transmission rate of 20 Mbps.

a token is needed in order for a ound a ring, the token is

passed in numerical order. If computer #1 is at one end of the network and Computer #2 is at the other, the token still passes in numerical order. Obviously, this can really slow a

r.

ARCNet transmits data in packets. These packets contain the destination address, the source address and up to 508 bytes of data. The ARCNet Plus architecture can hold up to

ARCNet utilizes hubs. These hubs may be passive, active, or smart. ARCNet can use stalled using RG-62 A/U coaxial coaxial cable and BNC connectors,

the maximum cable distance between the computer and the hub is 610 meters. This distance drops to only 305 meters if using the Bus topology. If using either the Star or

nnectors, the maximum cable distance is 244 meters.

inexpensive network architecture that may use a Bus o

charted to the 802.4 standards (Token Bus LAN). It uses a token-passing access mthat transmits at 2.5 Mbps. A later version, called ARCNet Plus, has a

Just like other token-passing access method architectures, computer to transmit data. Instead of the token traveling ar

network down if the computers are not in orde

4096 bytes of data.

twisted-pair or fiber-optic cabling, but is normally incable. If using an active hub in a Star topology, with

Bus topology with UTP and RJ-45 or RJ-11 co



IEEE 802.11 is the latest generation of enterprise-class wireless LAN technology. Speeds up to 54 Mbps will be available within wireless networks (LANs to be more specific).

ction in their own band (in the GHz range, generally). The capacity to use wireless technology is there for large-scale deployments as well. Wireless technology is discussed in further detail in chapter four.

Wireless (802.11)

Interference can be lessened by their ability to fun



Summary This has been another information intensive chapter and we covered a lot of information on the different networking architectures. Managing network data is all about traffic control, and the access method (such as CSMA/CD, CSMA/CA, Token Passing and Demand Priority) is the governor of how traffic is controlled on a network. It is important for the networking professional to understand the characteristics of each access method.

Data is sent out on the network in smaller chunks of data called packets (or frames). If it were sent out in one continuous stream it would quickly bring network traffic to a halt due to the large size of the data. Packets will include information to identify the source address, destination address and the actual data that is being transmitted. Most packets also include error checking or CRC (Cyclical Redundancy Check) methods to check the reliability of the packets received. Packets consist of three components: the Header, which includes an alert signal that a computer is transmitting, the source and destination addresses, and clocking information; the Data; and the Trailer, which is where the error checking calculation is located.

The popular Ethernet architecture is defined in the IEEE 802.3 standards. As a networking professional you will encounter this type of network most often. Therefore, it is important that you are knowledgeable about the different types of Ethernet such as 10Base2, 10Base5, and 10BaseT. The 100 Mbps and Gigabit Ethernet architectures will be even more prevalent in the future. It is extremely important that you understand the different cabling schemes and their connectors as well as the maximum segment lengths for all of these different architectures.

Although Token Ring is not as popular as Ethernet, it is still a common architecture and is said to be increasing its market share by as much as 20% per year. Be sure that you understand how this architecture works, as well as the different cabling schemes and cable distances, etc.

AppleTalk and ARCNet architectures may be used less than Ethernet or Token Ring, but as a networking professional you will encounter them. It is important that you understand their specifications and access methods as well.

Be sure to complete the following exercises and review questions. If you are having trouble with any of these concepts, go back and review the chapter again.




Keyword Definition

Access Method

AppleShare

AppleTalk

ARCNet

Beaconing

CRC

CSMA/CA

CSMA/CD

Demand Priority

Ethernet

EtherTalk

Frames

Header

Hub

LocalTalk

Multistation Access Unit

Packets

Patch Cable

Smart Multistation Access Unit

Token Passing



Keyword Definition

Token Ring

TokenTalk

Trailer

Zones



2. Describe the difference between the two different contention methods, CSMA/CD

at he same time?

6. How is data transmitted over the network cable?

10. What is the maximum segment length in 10Base2?

11. What type of connectors are used in 10Base5?

12. What type of cable is used in 10BaseFL?

Review Questions Chapter 5 1. What are the three primary access methods?

and CSMA/CA.

3. Why isn’t token passing considered a contention method?

4. Describe how data is transmitted in the Token Ring architecture.

5. What happens if two computers using the demand priority access method transmit exactly t

7. What is CRC and what part of the packet is it usually located in?

8. What sort of information do packet headers contain?

9. What does the “T” in 10BaseT indicate?



13. Name the two main 100 Mbps Ethernet Standards.

14. Which IEEE Specification defines Ethernet?

15. Which IEEE Specification defines Token Ring?

16. What are the two transmission speeds of Token Ring?

17. How are data collisions avoided in the Token Ring architecture?

18. Describe beaconing as it applies to Token Ring architecture.

19. Which way does data travel in a Token Ring network?

20. What is a SMAU?

21. Describe a MIC connector.

22. How does a computer on a LocalTalk network obtain its address?

23. What is the purpose of AppleShare?

24. What type of access method does an ARCNet network utilize?

25. How does data flow in an ARCNet network?



Chapter 6 – Network Design


Chapter 6 – Network Design In this chapter we are going to put to use many of the terms and concepts that we studied in earlier chapters of this training guide. We will start by looking at what it takes to layout a network from scratch. Then we will study in more detail network adapter cards, how they are installed and how to troubleshoot them. Finally, we will consider hardware compatibility. Hardware compatibility is a major consideration in network design andoften the source of troubles when expanding or upgrading networks.

is

ect

ere

their needs is essential when

any,

Starting a Network ProjA unique opportunity for any network professional is to design a network from beginningto end. For most of us this will be a rare event since most companies already have a network and are working with expanding or increasing the performance of what they already have. The most important aspect of creating a new network is to document everything that you do. This is especially true if you will be maintaining or upgrading thisnetwork in the future. (If not, whoever is assigned the upgrade project will be forever indebted to you.

The place to start a new network is with a pad of paper and a pencil or two. Even if this network is your own, rather than a client’s, you need to approach the project as if it wfor someone else. This will give you the discipline to ask yourself the right questions and to begin the process of documentation. There are two things that you will need to know.

The Customer

Obtaining a clear understanding of your customer anddesigning a network. As a network professional, you will have a lot of knowledge andexpertise with networks. This is well and good if you are designing a network for your own use. However, in many cases, you are not designing for yourself. You could design the best high-speed low-cost Windows system that was ever imagined, but if your customer is a Macintosh user, your design will not work for them. The following is some suggested information that you should gather about your customer:

The basics – name, address, etc. (demographics).

The size of the company and the portion of the network affected.

The product – this is very important as a graphic arts client will have different needs thanan engineering firm or a law office.

The facility – how big is the building(s) and what is the layout of the various offices?

Current level of technology – how many computers do they have, who has them, are there any printers or scanners, etc? If, for example, this is a Macintosh-based compyou certainly don’t want to design a network around Windows. Most importantly, pay attention to details.

The customer’s likes, dislikes, and goals.



LAN or a complex WAN with Internet and remote users?

A business office moving eets across a network will generate far less traffic than a

g files. For example, a text-le a single page image file

h as 8 MB for the same image en more if color or grayscale). So,

the network need to provide? Sharing of resources, files

am like Microsoft Paint, or as

rmation in hand, you are now ready to begin the designing of the network.

The Network Goals

In addition to the customer’s needs, you must get a clear definition of goals of the network. The following are some questions to consider:

Will this be a simple

What are the future needs? Is this network to start small and expand later, or will it meet the requirements of the latest technology?

How much traffic do you anticipate now and in the future?1000 documents and spreadshgraphic arts or engineering office moving 1000 large imaginonly MS Word file will be approximately 30 KB of data whiwill average 50 KB, if the file is compressed, or as mucscanned (black and white) at 300 dpi uncompressed (evthe same 1000 documents could be as little as 30 MB, or as large as 8 GB.

Is an Internet connection needed now or in the future? Will it be for all users or just a select few?

What additional services willservices, print services, etc.

Once you collect this information, prepare a design document. Your document should include a summary of all the information you collected. This can be done using any word processor or spreadsheet program. You may want to consider using a drawing program to create a layout of the facility. This can be a simple progrcomplex and as expensive as AutoCAD. There are many intermediate drawing packagesthat are available. A good intermediate program is Visio 2002. This program provides simple templates for both facilities and network components. Remember, at this time, you are not documenting your network, only documenting the facility and the requirements of the network. You will need this information as you make decisions in the next few steps.

With this info





etermine Network Type Once you collect all t start making some decisions. The first is the type of network you will be designing. Here you will have two

server. The decision that you make at this time will have an affect on the hardware and software choices that you make in the future. You will

nsideration of st you with this decision. The following lists the information that you will need in order to

oose your network type. If you do wrong choice now, may cause problems in the future.

r of nodes (computers and

The level of security required. This can rangeme level of security.

The type of business and how that wi etwo

Skill level of the network users. Are they able to handle a sophisticated network or must be transparent to them?

The available budget (both now and

The commitment of management andgoing to resist the change?

When to Choose Peer-to-Peer

There are many reasons why you would want toare simplicity and cost. In a peer-to-pprovide services to the network and use services provided by others. For example, if you have a printer connected to your comwho has access to the network can se if a coprinter and you don’t, you can send wthey share the printer to the network)

Peer-to-peer networks are economicahigh-power computer with lots of speed and processing power. Most personal computers

ore than enough poenvironment. You may have to add netwsystems like Windows 95 and up and include the necessary software and pinstall the software, as generally it is not installed during a standard installation. As long

k have prob t you m ix two different operating systems without additional software or upgrading to a client/server netwo

The disadvantages of peer-to-peer networks are security and limited network size. Peer-to-peer networks do provide some security in the form of allowing you to select what you want to share to the network. This sharing is on a directory level. This means that every

Dhe information described above, you will need to

choices: peer-to-peer or client/

need to take careful co the information collected in the first step to assi

ch not have this information go back and get it. The

The numbe other resources) on the network.

from none to very high. Also, not all nodes may need the sa

ll affect n rk traffic.

the network

in the future).

users. Are they committed to the change or are they

choose peer-to-peer. The most prominent eer network, all computers are equal. They can

puter, you can share it to the network and anyone nd work to it. Likewise, lleague has a color ork to it if you need color printing (assuming that

.

l to setup and implement. First, they do not require a

today will have m wer to successfully operate in a peer-to-peer ork cards and cabling, but most operating

Macintosh OS X are “network ready.” That is, theyrotocols for file and print sharing. You may need to

as you have the original software disay not be able to m

(CD), you will no lem. Keep in mind tha

rk.



fshould be limi u can connect more

workstations, but there will most like ductions in network performance as stations are added. In a peer-to-peer situation, if anyone is using a resource on your workstation,

r printer, they will also be e result will be a slow-down of performance on your workstation. This will be especially true if your workstation is using an older, sl

In a small network where everybody peer-to-peer network may be the perfect somay consider this type of network as

When to Choose Client/Server

On a client/server network (also known as server-based networks), all network resources are usually centralized. This means thand provide the resources for the entire network. Since these computers are larger, have high-power processor, and lots of memory, the performance of the network will be better than in a peer-to-peer network. Anothservers are never turned off. This means that if you need to use the color printer that is connected to the print server, you wilcomputer is turned off (since she is the only one pany that h

Using a file server to maintain all of individual workstations, is another adfile system also makes for easy transfday. Also, if employees need remote access, information can be made available to them through a RAS (Remote Access Server) connection.

Perhaps the most significant aspect o sed ne worksserver-based networks provide a central dataas well as the network itself. Before yauthorization to use the network and r sourcepeer network, any user can log on to a workstation (with a new name and password) and gain access to the network. In a servecreate a user name and assign permissions to that user.

Last but not least, server-based networks are scaleable. This means that you can start all with one server and a few work expand.

While there are many advantages, you will also need to consider the disadvantages. The most prominent disadvantage is the cost to install and operate the network. It is obvious that server-based networks will require better and higher-powered hardware, but what is often overlooked is the cost to administer the network. The more sophisticated the network, the more knowledgeable the administrator needs to be. Most employees have little or no knowledge of the workings of computers, must less the workings of a network. For these people, the network must operate transparent to them. In small networks, all that is needed is one or two knowledgeable people to act as administrators. Remember, this will take part of their normal workday will be taken up to react to any problems and maintain existing accounts, etc. In large networks, administration can be a

ile in the directory will be available to the peer-to-peer networks

network. As for size, the general rule is that ted to about 10 workstations. Yoly be re

such as you using your processor to do their printing. Th

ower processor and/or has limited memory (RAM).

knows each other and security is not an issue, a lution. Also, a client with a limited budget

a starting point or entry-level network.

at one or more computers are designated as servers

er advantage of server-based networks is that the

l not need to worry if Mary is on vacation and her in the com as a color printer).

the company-wide files, instead of backing up vantage of a server-based network. This centralized ers of files throughout the company, 24-hours per

f using server-ba t is security. These base that manages access to all the resources

ou can use any resource, you must have both the permission to use the e . In a strict peer-to-

r-based network, only a network administrator can

sm stations, and expand as your needs



full-time job for one or more people and may even require the skills of a certified network professional. Each network operating system supplier has their own certification program such as Microsoft’s MCSE (Microsoft Certified System Engineer) and Novell’s CNE (Certified Novell Engineer).

Making the Choice

Making that final decision is often difficult. In some cases, the answer will be very obvious; in others it could go either way. When you are sitting on the fence, be sure to follow a disciplined procedure:

Collect all your information.

If you are not sure you have enough information, get more.

Prepare a case (on paper) of the pros and cons of each.

If all else fails, present each case to the client and let them make the final decision.

Once you have made this decision, stick with it and move forward. This decision will be the basis for the rest of your network design.

Public and Private networks

In addition, let us define the difference between the terms public and private network, since your organization will more than likely need access to the Internet and networks outside of their LAN. A private network would be a corporate network or an Intranet, which would limit its access to those outside of the company. A public network would be the Internet, with open access to the global community.

Actually, you can use any address that you want to use inside of your own network and behind your firewalls. The only problem is that if your firewall were to come down, then you might have an address conflict with another entity on the Internet. For this reason, there are specific addresses that are filtered by the routers at the backbone of the Internet. The use of these addresses will completely prevent the address conflict issue. For this reason, it is highly recommended that you use these addresses for your private addressing.

10.0.0.0 -10.255.255.255 255.0.0.0

172.16.0.0 -172.32.0.0 255.255.0.0

192.168.0.0 - 192.168.255.255 255.255.255.0





designing a network from the ground up and literally starting with a blank

umenting of existing equipment includes two components: hardware and ply

mation you need may be inside the machine and you will have to

piece of equipment. This form

sheet. Feel free to use this as a starting place for

Define the Starting Place

If you arepiece of paper, you can skip this section. On the other hand, if all or part of a network already exists, you will need to make a detailed inventory of the materials you already have. You may also want to take an inventory as part of your initial evaluation.

The docsoftware. When taking this inventory, whether hardware or software, don’t just simask someone what he or she has, ask him or her to show you. Remember, this is a detailed inventory that requires someone that is knowledgeable in computers and networks. That person is you! Be sure to take a small toolkit and a flashlight with you. Some of the inforremove a case or two.

The best approach is to make an inventory sheet for eachshould identify the equipment and its specifications. The following page shows an example of what an inventory sheet might look like. Use it as a starting place to build your own. Also, if you are creating a new network and have no inventory to work with, you must add new hardware, use this sheet to define your proposed new equipment. The following is an example of an inventorydeveloping your own customized form.



Network Equipment Inventory Sheet

Item Number: ___________

Type of Equipment: Computer Printer Telecommunication Other

If Other: _______________________________________

Location:

Identification: Make: ____________________________

Model: ____________________________

Serial #: _____________________________

Computer: Processor (Type and Speed) ____________________

RAM ____________________

Hard Drive(s) ____________________

Monitor ____________________

Video Card ____________________

Modem ____________________

Connected Peripherals ____________________

Bus Type (ISA, PCI, etc.) ____________________

# of Free Slots ____________________

Network Card ____________________

Printer: Installed RAM ____________________

Interface (Parallel or SCSI) ____________________

Network Compliant (Yes/No) ____________________

Peripheral: Type of Device ____________________

Interface (Parallel or SCSI) ____________________



Describe the device and its function. Telecommunication:

If this device uses software, describe each program.

Name of Program:(Operating System) __________________

Version Number: ____________________

Licensing Information: ____________________

____________________

Original Disk (CD) Available: ____________________


____________________

le: ____________________

Name of Program: ____________________

Version Number: ____________________

Original Disk (CD) Availab

Software:

Name of Program: ____________________

Version Number: ____________________


____________________

Original Disk (CD) Available: ____________________

Use additional paper if necessary.





he

n ment. This might be a good time to start identifying

umber. By assigning them a number now, it will make future

Design the Network At last we should have enough information to start designing our network. It is time toget out that pencil and paper, or the software drawing program that you used to create tlayout of the facility, and collect all of the documentation you have been working on. Using the inventory sheets and the objectives of the network, make a drawing of the facility and each network node. Start with the location of existing equipment (if any) thedraw the location of the new equipeach node with a name and ndocumentation easier.

A Network Layout



will meet the performance criteria of the network. For example, a small network with only a few

s and printing will probably work fine with CAT 5 UTP cables. ,

to be advantage of its 1000 Mbps speed. In addition, if you are not sure if

igning a small temporary LAN, e in n the

t forget to terminate each end).

al star topology, you will need to remember that all cables

ore

Media Selection

Media selection is an aspect of installing a network that should not be taken lightly. It is the most labor-intensive of all the processes and the most costly to replace. The most important aspect of media selection is to be sure that the media you choose

workstations sharing fileThe 100 Mbps speed of this media will handle this workload without problems. Howeverif you are going to have hundreds of computers or transfer large quantities of large files, such as in an imaging environment, you will need to install CAT 5e or CAT 6 UTPable to takeexpansion is in your future, it would be worthwhile to spend a little more now and install CAT 5e or CAT 6 than to replace it in 2 to 3 years. Realistically, CAT 6 is the UTP of choice.

If economics are a major concern and you are desconsider Thinnet coaxial cable. These cables are inexpensive and if all computers arthe same proximity, a simple bus topology with each computer in a series will save obudget (don’

Cable lengths must be considered. If you intend to use UTP or STP cables, you must make sure that the longest connection (computer to computer, or hub to computer) doesnot exceed 100 meters (328 feet). In most environments this will be no problem, but if this is a large facility, and the run from the server room to the maintenance shop is 400 meters (1312 feet), you will need Thicknet coaxial cables.

On the high end, where money is no object and security is critical or you have long distances to cover, (up to 2 kilometers – 6562 feet) choose fiber optics.

The following are several other factors that must be considered before making your final choice:

Topology – If you use a physicmust originate from the hub. Therefore, hub location is critical for determining cable lengths.

Cable Grade – Local fire codes, or just good common sense, may require that you install plenum grade cables for part or all of your installation. It may be more cost effective to purchase a large quantity of plenum grade rather than a mix of plenum and standard grade.

Cable Type – If your goal is to save money now and you don’t need a high-speed network, you might consider CAT 3. However, for long term use and eventual upgrade to 100 MHz, the cost of CAT 5 is not significantly more than CAT 3. It will cost a lot mto upgrade later.

5-4-3 – If your installation is coaxial Ethernet, you must comply with requirements of the 5-4-3 rule for number of segments, repeaters and nodes.



f the installation is located in an industrial environment (vibration

ng) you should consider alternatives like fiber optics. Fiber optics are also a ity of

ten overlooked when designing a network is the actual

midity, d

and available, such as a surge

suppressor and an uninterruptible power supply.

NOS Selection

is a matter of user preference. Most network operating systems today are robust and will operate transparent to the users. Therefore, on the surface, it doesn’t really matter. As long as it is configured well and meets the needs of the customer, it will work. On the other hand, sometimes the customer will make the choice for you. If the customer has always used Novell NetWare and is satisfied with the performance, it may not be prudent to recommend the change to Windows 2000/2003.

Protocol Selection

The most important issue with selecting a protocol is to use the same protocol throughout the network. The next choice is whether to use a routable or non-routable protocol. The non-routable protocols, such as NetBEUI are simple and work well with peer-to-peer networks and small LANs. However, if you intend to work with a larger network or WAN, which requires the use of routers, you need a routable protocol such as TCP/IP. These routable protocols are more difficult to configure, but are not limited.

Noise – If all or part oand noise), or uses lots of electrical or electronic equipment that generates EMI (electromagnetic interference) or RFI (Radio Frequency Interference), you may need to install fiber optics at least in that area.

Environment – If all or part of the network is in a hostile environment (corrosive - manufacturigood alternative when the manufacturing environment cannot allow for any possibileven a small spark, since they don’t use electricity to transmit a signal.

Environmental Concerns

A major concern that is ofenvironment in which the computers will be operating. Like us, they are sensitive to temperature changes. Fortunately, the same conditions that are good for people are often ideal for computers.

Constant temperatures of around 70° F, with a relative humidity of 30 percent, are usually what is found in the office environment where most networks are installed, and this is also the ultimate atmosphere for a computer. Variable temperatures, low-huwhich can generate damaging ESD, high-humidity, which can cause corrosion, anfluctuating line-voltages from the incoming power source, can all cause a computer to fail or behave erratically. Less than ideal conditions will also decrease the life expectancy of your equipment.

Most larger companies will have a dedicated room for their server (the Server room), which is kept at the ideal temperature for the equipment. It is not strictly necessary to have a dedicated room for the equipment, but it is important that the room be well ventilated and climate controlled. The equipment should be shielded from ESD, EMI,RFI, and should have a method to ensure that clean power is

Choosing the network operating system





cable

ialist

e T 6, it t

e t

puter on every outlet. The hub will know that the cable is not ignore it. This way, you can install future or optional locations

Putting it all together Installing the media is a task that is often best left to someone who specializes in installation. So let’s assume that you or your specialist has run all the cables. There are a few more components that need to be installed. Make sure that either you or the specmarks each cable at both ends. This way you can identify each location.

Cable to Computer

Depending on the selection of cable, you will most likely need to install a wall outlet. Thtype of outlet will depend on the type of cable. In most cases, if using CAT 5 or CAwill be a wall plate with an RJ-45 outlet. These outlets will make for a nice and neainstallation and will make the room ready to connect a computer to the network. The next step will be a patch cable that runs between the network adapter card and the outlet. Onthing to remember about these patch cables is that their length must be considered as parof the overall length of the cable.

One advantage of using CAT 5 or CAT 6 cable in a star topology from a hub, is that you do not have to install a comconnected and will simplyin preparation for expanding.

Connecting to a computer

Cable to Hub

The connection of the cables to the hub will usually take place in the “server room.” This is a centrally located room or closet that will house the primary server and hub. All the cables will be brought to one location. To keep these organized, the cables are connected to a patch panel. This is just a strip of RG-45 connectors. Each cable is in turn connected to one of the outlets and a patch cable is then used to connect it to the hub.



Connecting to a Hub

Network Adapter Cards

Installing the cabling for a network is literally installing the Physical layer of the network. Once that is done, there is one more part of the Physical layer that must be installed. That part is the network adapter card. This card is a circuit boardelectronic circuitry and components necessary to physically connect to the computer and the m dia. Because it must connect to both the computer and the media, we must select a card that is compatible with both. Therefore you must know the requirements of each.

ctually, there are three things to consider:

ility

with all the

e

A

• Network Compatib

• Media Compatibility

• Computer Compatibility

Connecting to a NIC





atibility uilding across-the-

board compatibility for hardware and software at the design stage will simplify future i k together is

to the cost and time requirements of maintenance, administration, and expansion projects. This section will look at compatibility issues.

A network card acts as the interface between the computer and the network. Therefore, there are compatibility issues on both sides of the interface.

Card to Network

ard (NIC) must be able to rotocols as the other

components. If you are installing a Token Ring network, you must have Token Ring cards. An Ethernet card simply won’t work on a Token Ring network. Also, the speed of

s netwo

In addition to being compatible with the network, the card must be compatible with the computer. Resolving these issues is actually quite simple, but requires some knowledge of the inside workings of a computer. The processor (CPU) in a computer will

f parcom e number of connectors, and therefore the speed at which data can be moved, will change. Network cards are designed to meet the standards of the bus.

e of the of gold “fingers” that fit into the slot to provide the electrical connection. The different types of cards are designated by the orientation and number of these connections. There are four

Before purchasing a network card, you will have to know the type of expansion slots used in the computer and whether or not there are any free slots. The best way to find out is to remove the case and look.

Note: Laptops and proprietary computers will have special cards designed to fit their

Network and Hardware CompNetwork compatibility is a key consideration in network design. B

ma ntenance and troubleshooting. Making incompatible components worpossible in most instances, but in the long run this will add significantly

Adapter Card Compatibility

Network adapter card compatibility is simple. The adapter ccommunicate on the network using the same standards and p

the card is important. For example, a 10 Mbps card (10BaseT) will work on a 100 Mbpwork (100BaseTX), but only at 10 Mbps. Some of the newer 100BaseTX cards will rk on a 10BaseT network, but only at 10 Mbps.

communicate with the expansion cards through the expansion bus. This bus is a group oallel conductors that carry digital information to and from the CPU to all parts of the puter. Depending on the vintage of the computer, th

The actual connection between the card and the bus is called an expansion slot becausway the cards are installed. On one side of the circuit card are a group

types of cards that you will encounter (ISA, EISA, Micro Channel, and PCI).

architecture. Laptops generally use PCMCIA cards, also called PC Cards.

Some network cards provide diagnostic lights, which can be a useful tool. These are little LEDs (one, two, or three) that indicate the status of the card. Not all cards are the same, so you will have to check the documentation to be sure of their meaning. In general, a



green light indicates that a proper network connection exists and a flashing yellow light indicates that data is being transferred. Keep in mind that a green light does not mean that the computer is properly configured and you can use the network; it only means that the proper connection has been established between the card and the network.

Card and Computer

Installing a network adapter card is not any different than installing any other expansion card in a computer. Understanding the installation process is the key to preventing conflicts.

The details of installation will vary depending on the type of computer and the operating system installed. Since describing the installation of a network adapter card for every system is beyond the scope of this training course, the following is a generic procedure that defines the key points that you must follow:

Purchase the card. First ensure that it is compatible with your system (network and computer).

Configure the IRQ and I/O address. In most cases with a new card, this will be done with the installation software or by the operating system. If your system is not Plug-n-Play, you may still have to manually set some jumpers or switches. If you must do this manually, be sure that no other device has already been assigned the IRQ or I/O address. If there are any conflicts, the computer may not boot or the conflicting devices might not be able to work simultaneously.

Physically install the card. Remove the case and install it into a free expansion slot. Note: If you must remove the case, be sure to follow ESD (electro-static discharge) procedures. Hint: you may not want to put the case back on until you have confirmed that the card is working.

Connect the network cabling.

Install the appropriate drivers for the card. Drivers are usually supplied with the network card. Many operating systems already include drivers for most network cards. If you don’t have the driver or want to make sure that you have the latest driver, you can usually download them from the manufacturer’s web site. In addition, if you upgrade your operating system, you may need to download a new driver in order to make it work or to increase its performance.

Now the network adapter card is installed, but you are not finished yet. You need to configure the card to work with your network software. You still need to bind the card to the network protocols that you are going to use. Finally, you will need to check the documentation for the network operating system that you are using.

Note: Many computers that are designated as servers or gateways can have more than one network card installed. Each card must be configured for a different network.



Media Compatibility

connect to the card. In the case of UTP, the card should have an RJ-45 connector. For Thinnet or Thicknet, the card

en Ring uses a DB-9

connector.

some manufacturers will provide two, and

elect the best buy of the day. While this makes good sense to the accounting dep m te havoc when you have to connect them and actually have them communicate. You may have to connect some older “legacy” hardware with some new hig p th highly departmentalized companies is that each department has its own preferences. For exa ent may be Macintosh-based, the engineering department may be PC-based, and the administrative department may just be thankful for hav heir hands on.

es of each scenario, as well as possible solutions.

Media compatibility is the ability of the cabling to physically

must have a coaxial BNC connector. Some STP cards require special connectors. Forexample, AppleTalk employs a DIN-type connector and IBM Tok

To increase marketability of their cards,possibly three, different connectors allowing for multiple installation scenarios. The bottom line is to be sure to look before you buy.

Computer Compatibility

Computer compatibility is often a serious problem encountered when installing a network in an existing facility. Many growing companies purchase their computers only as needed and will s

art ent, it can crea

h-s eed high-tech machines. A typical problem encountered wi

mple, the graphics arts departm

ing whatever they could get t

These types of problems can be more personal in nature, as some individuals will not want to change their way of doing things just to have a network. If you encounter this type of situation, the decision may end up with the company’s management and you will have to work with it. However, it is your responsibility to point out the strengths andweakness



roblems lity issues; hard work and

standards.

Har

Har y allies when it comes to setting up a network from an existing system. Unless you are very lucky and are installing a new netw ridentically configured, you are going to have your work cut out for you. Your only rec s

f

Earlier in this training course, we learned about network protocols and standards. Standards are one way in which hardware and software suppliers can develop a product and be assured that it will work with the f other suppliers. As long as the system is designed to meet the same sta h component will work with the

designer or administrator, you will need to establish the standards

Preventing Compatibility PThere are really only two methods of resolving compatibi

d Work

d work and attention to detail are your onl

o k, with identical computers that were purchased from the same supplier, that were

our e is to document every computer and piece of hardware that must be connected tothe network, and detail both its hardware and software. This will most likely require that you remove covers and identify components such as the modem and the network card, ifinstalled. You will also need to know the type of processor and the type and number oavailable expansion slots. With this done, boot up each computer and note the operating system and any installed software.

With this information in hand, and knowledge of the network operating system, you should be able to predict potential hardware compatibility problems and take action to prevent them.

Standards

products ondards, eac

others. As the networkfor your network. By defining the standards to which the network must comply, you will be assured that any new additions will function properly.



Resolving Compatibility Problems No matter how careful you are, sooner or later you will encounter compatibility problems. The networking industry is in a constant state of change and unless you want to be left behind, you will need to upgrade. Most hardware compatibility problems are resolved by installing the latest drivers. For example, when upgrading from Windows 98 to Windows XP, you find that your modem, network card and/or printer no longer work. More than likely, all you need to do is install the Windows XP drivers for the offending hardware. The first thing you need to do is determine if the original disks/CD that came with the device has the drivers to match the new operating system. If the operating system was released after you purchased the device, you probably do not have the necessary drivers. In this case, the Internet is the answer. If drivers exist, you will be able to locate and download them from the manufacturer’s web site. Also, there are several web sites that specialize in downloading drivers. Drivers for a particular device are not always available for all operating systems. You should always confirm the availability of drivers before purchasing an unknown device. Some devices do not have drivers for all operating systems.

Minimum Requirements

nsidering an upgrade or change of an operating system, you will ents

d

rate the system at a normal performance rate. A good example is Windows 95. Microsoft says that you do not need

When evaluating or coneed to check the manufacturer’s recommendations for the minimum requirements tooperate. These are the bare minimum requirements to run the system. These requiremby no means indicate what you should purchase, only that if you don’t meet these requirements, the system will not run. Most manufacturers will also publish suggestedminimum requirements. These will be somewhat higher than the required minimum anare what you need to ope

a mouse to run this operating system. This is a true statement; however, have you ever tried it? You can run Windows 95 without a mouse by using only keystroke ur proficiency will be very low. The

s require a mouse as one of the minimum requirements. s, but yo

later Windows operating system



he following table lists an example of the minimum requirements for three operating systems:

T

HCL and Windows 2000

To help alleviate compatibility issues some manufacturers provide HCLs, or hardware compatibility lists. An operating system such as Microsoft Windows 2000 is hardware dependent. It is considered an advanced operating system and will not work with all hardware. If you were to purchase an econo-version of a computer or one that is highly proprietary, it most likely will not work with Windows 2000. To assist in making an informed purchasing decision, or to confirm whether or not your existing hardware will work with Windows 2000, you will need to check the HCL for that product. This list will ship with the 2000 package (on the CD-ROM) and 2000 will make a check during installation. If you want the latest list, you can get it from one of Microsoft’s web sites.

Microsoft Windows Catalog

Still another web site to check for compatibility of hardware and software, especially with the newest operating systems such as Windows XP and Windows Server 2003, is the Microsoft Windows Catalog at www.microsoft.com/windows/catalog. Here you will find the latest information about hardware and software that is Designed for Windows XP and Windows Server 2003 or at least tested to be compatible with these operating systems. This is part of the Windows Logo program. You can also look for the corresponding logos on the boxes of hardware and software that you are considering purchasing for your network.





Review Questi s C1. What are the tw ols r ?

2. What are the two areas o

3. What are the two most p sons to choose a peer-to-peer network?

4. What is the num r one network?

5. Is NetBEUI a good protocol to use with a large WAN?

8. Your company just bought ten new computers and all are guaranteed to meet the minimum requirements of Windows XP. Was this a good purchase?

9. How do you know if a new piece of hardware will work with Windows XP?

on hapter 6 o to equired to initiate a network design

f concern when starting a network project?

rominent rea

be reason for choosing a client/server

6. Your client is installing a small Ethernet network and trying to save money at the same time. However, he intends to expand the network in the future. Give one reason why you should recommend that he spend a little more now and install CAT 6 cabling instead of CAT 5.

7. You are expanding your network and will need to invest in 50 to 100 new network cards. Your accounting office found a really good deal on network cards, but they are not all the same. Why should you refuse this offer?

Chapter 7 – Expanding a Network


Chapter 7 - Expanding a Network No matter how well you design a network, sooner or later, it may be his chapter will discuss several techniques for expanding a network.

Expanding a LAN with Hubs A common me xpanding networks is to use a hub. A hub is a device that acts like the centra ion for all com rs on the network. There are several different types of hubs, from five-connec bs used to connect five devices, to larger hubs that can connect ore computers. For example, you cannot use an Ethernet hub on a Token Ring network. In addition to being called “hubs,” you may ferred to as:

• Conc s

• MAU or MSAU– Multistation Access Unit (

• Patch

• SMAU – a Smart MAU

ubs can be either active or passive. An active hub will require power and will often rovide some form of signal conditioning (amplifies weak signals). Active hubs can be

s

too small. T

thod for el stat pute

simplemany m

tor hu

also hear them re

entrator

Token Ring)

Panel

Hpused to extend the length of network cabling by connecting them in a series. Passive hubdo not use external power and are used only to concentrate the cables in a common location.



• Too much network traffic.

• Long waits to access a printer or file.

• Traffic-generating applications, such as databases, have increased response times.

• You are just plain tired of your old system and want to get your system updated.

When the time comes to make a serious expansion to a LAN, the simple hub just won’t do the job. Depending on the objectives of the LAN, you will have to employ one or more different pieces of hardware. Fortunately, there are several other devices that can be used to expand a network. Each has its own unique advantages and disadvantages.

Repeaters

A repeater is a device that is used to extend the cable length on a network. They do not translate or filter any information. They do however, amplify the signal, thereby compensating for signal loss due to long cable lengths. Repeaters work in the Physical Layer of the OSI model.

When a LAN is Too Small There are several reasons to consider expanding a LAN:

Repeater

Bridges

A bridge does the same things as a repeater, but has one additional feature. A bridge can be used to isolate segments on a LAN, thus reducing the traffic for each segment. Bridges work in the Data Link Layer of the OSI model.



Bridge

Routers

A router has all of the features of a bridge, but it can switch packets across multiple networks. Routers can also determine the best path for “routing” traffic and filter

traffic on the local segment. Routers work at the Network layer of the OSI t all network protocols will work with a router. For example, the NetBEUI

broadcastmodel. Noprotocol is not routable.

Router

Gateway

Gateways make it possible to connect different network architectures. Think of a gateway as a computer that acts as a translator between two networks that don’t speak the same language. It is an entrance to another network that controls traffic on your network.



Gateway

Connection Services When expanding a network beyond the local area cable boundaries, it is likely that you will need to connect to a third party’s cabling system. An example of such a system is the telephone company. When considering which connection service to use, be sure to take into account your throughput, the distance the data must travel, and the cost of the service.

Carriers

Carriers are the companies that we contract with to carry our data over long distances. They are providing the cabling, microwave, and satellite connections. When thinking of a carrier, we most commonly think of our local telephone company or one of the long distance carriers. Keep in mind that there are many carrier companies that provide many

ifferent services at a variety of rates. Be careful when choosing a carrier. Be sure to pare them on an equal basis and look for hidden costs. Just because the cost looks

t mean that it is the best value.

s

ed

dcomgood, does no

When thinking of telephone lines, there are two levels of service to consider. The first ipublic dial-up network lines. These are our standard telephone connections. With dial-up networking, each computer must use a modem and establish a direct connection. Typically, these connections are slow and not very reliable. Some of the newer digital services will claim to have a speed of 56 Kbps, but connecting at this rate is rare. The second choice is leased, or dedicated, lines. These powerful full-time dedicated connections do not use a series of switches to complete the connection. Speed for leaslines can reach 45 Mbps.



N need to be exceeded, items

AN link to connect LANs will need to use CSU/DSUs. A CSU/DSU hannel Service Unit/Data Service Unit) is a hardware device responsible for changing

the frame typ tever th N is using into a fra will work on the WAN. It also chang e type back when frames are sent

The CSU is re for bot i se transmitted to it. The DSU is responsib ut and output between the framnecessary, and deals with timin

You can also adapt y.

Communication between LANs will involve one of the following technologies:

• Analog

• Digital

• Packet Switching

Analog Connectivity

Analog commu n is the sed on PSTN (Public Switched Telephone Network) lines and dedicated analog lines.

WAN Overview

When the physical capabilities and distance limits of a LAsuch as bridges, routers and communications services are used to create a WAN. These physically larger networks will appear to function the same as a LAN. Most WANs are acollection of LANs. WAN links can include any of the following:

• Cable Television Coaxial Systems

• Fiber-Optic Cable

• Microwave Transmitters

• Packet Switched Networks

• Satellite Links

Those using a W(C

e from whaes the fram

e LA me that back.

sponsible h the s gnals received from the WAN, as well as thole for converting both the inp

e types between the LAN and the WAN. It can regenerate the signal, if s. g issue

use ISDN ers if you are using ISDN PRI for WAN connectivit

nicatio one that we are most familiar with. It is ba. There are two types of PSTN: dial-up



Analog Signal

The dial-up lines can be further classified as:

Line Type Description

1 Basic voice.

2 Voice with some quality control.

3 Voice/radio with tone conditioning.

4 Data applications below 1200 bps.

5 Basic data.

6 Voice and data over trunk circuits.

7 Voice and data over private lines.

8 Voice and data over trunks between computers.

9 Voice and video.

10 Application relays.

Dedicated analog lines provide an instant connection. This is because you lease the line 100% of the time and therefore do not have to dial-in. The down-side of these lines iyou will have to pay for them 100% of the time instead of on an “as used” basis. Dedicated lines are far more expensive, but if you have sufficient traffic, they can be justified.

Digital Connectivity

s that

When you need a faster, more secure line than can be provided by an analog connection, you need DDS (Digital Data Service). The primary reason for using digital lines is that they are 99% error-free.



Digital Signal

T1 is the most widely used type of digital line. It is capable of 1.544 Mbps transmissions. It can be used to transmit digital voice, data, and video signals. The following table lists the most common connection types:

Connection Type

T1/E1/OC1 Channels

Voice Channels DATA RATE (MBPS)

T1 1 24 1.544 Mbps

T3 28 672 44.736 Mbps

E1 1 32 2.048 Mbps

E3 16 512 34.368 Mbps

XDSL N/A N/A Varies depending ISP; faster download

than upload

OC-1 1 N/A 51.8 Mbps

OC-3 3 N/A 155.52 Mbps

ATM N/A N/A Either 155.520 or 622.080 (can reach 10 Gbps)

The 1 he E1 and the E3 are the European standard.

T and the T3 standard are American, whereas t



Cir t

Circuit-switched networks set up a continuous direct connection between the individual calling and the one being called. POTS (Plain Old Telephone Service) or the telephone line r ype of network. Obviously, since the infrastructure of the phone line we use today was created long before the advent of the personal computer and the Internet, this particular type of network is not suited for most

ard PSTN lines have a very limited bandwidth of less y

cui -switched Networks

s a e the most common example of this t

companies’ business needs. Standthan 56 Kbps. These lines can, however, be used for somewhat secure remote access bemploying the use of virtual private networks (VPNs) and tunneling protocols.

Circuit-switched Network

Pac t

Pac t roviding fast, convenient, and reliable network me g ovides multiple paths that packets could travel fro based packet switched networks, each packet wa in the path to determine whether it was damaged. This made for a very reliable and very slow connection. Today’s networks use a different technology

to as Frame Relay. With Frame Relay, a packet may be sent over multiple h are considered reliable. For this reason,

le

ke Switching Networks

ke switching is a means of pssa ing. A packet switched network prm source to destination. In older, X.25s examined at each step

referredpermanent virtual circuits (PVCs), all of whicFrame Relay does not check the packet at each step in its route, so it can be both reliaband fast.



Packet Switching

ysical

printers, etc.) by another means apart from how they are connected physically and VLAN based on certain departments

puters, or any other logical means. ers or

VLAN

Virtual LANs (VLANs) can be viewed as a group of devices on different physical LAN segments that can communicate with each other as if they were all on the same phLAN segment. It is best understood as a “logical” LAN, which lays out hosts (computers,

geographically. An administrator might set up a within his company, or by the specific use of the comThis allows the administrator the luxury of modifying the VLAN, adding computadjusting resources, without having to change the physical picture of the network. This type of network is most closely associated with a “campus environment.”



VLAN

ATM - Asy h These cells can s know exactly what to expect in re r perate at a throughput te at as high as 622 Mbps h t media dependent r, media

he and will require special hardware and bandwidth to

was 00

od choice for LANs that require large bandwidth and it will provide a secure network that is

ce.

n

home or small business, has two 64 Kbps

Advanced WAN Environments

If the existing services available do not meet the needs of your WAN, you might considersome of the advanced WAN technologies. One of these may just provide you with the necessary bandwidth and speed that you need.

nc ronous transfer mode uses fixed length (53 byte) cells instead of packets. speed communication because the network alway

ga d the size of the next cell. These systems are designed to ora of 1.2 Gbps. However, in actuality, they currently operate

wit most commercial boards operating at 155 Mbps. ATM is noand will operate on coaxial, twisted pair, or fiber optic. It is, howeves means that the choice of media will limit the maximum speed of tlimited. Thi

network. ATM is relatively newreach its full potential. As well as the common voice and data, ATM can be used with FAX, video, audio, and imaging.

FDDI - Fiber Distributed Data Interface is the basis of fiber optic communication. Itdesigned specifically for Token Ring networks and has a maximum ring length of 1Kilometers (62 miles). It will support 500 computers and run at 100 Mbps. While not a good choice for WANs, it is a gohigh speeds. Because it is fiber optic-based, immune to interferen

ISDN

Integrated Services Digital Network was one of the early digital services, and focuses othe home and business market, while using copper telephone wires. ISDN BRI (BasicRate Interface), which is intended for use in the



B-channels for data or voice (128 Kbps), and one 16 Kbps D-channel for control. ISDN PRI (Primary Rate Interface), which is intended for use by large businesses, has twenty-three 64 Kbps B-channels for data or voice (1.544 Mbps), and one 64 Kbps D-channel for control.

SMDS

SMDS - Switched Multimegabit Data Service offers high bandwidth at speeds of up to 34 Mbps. This service is provided by some local companies and works well for MAN installations (compatible with IEEE 802.6).

SONET

SONET (Synchronous Optical Network) is a fiber optic-based technology that specifies the speeds at which the equipment can multiplex signals from sources into high-speed carrier devices. It includes a set of signal rate multiples for transmitting digital signals on optical fiber (OCx). It is capable of transmitting voice, data and video at rates rang g from 51.84 Mbps (OC-1) all the way up to 40 Gbps (OC-768).

SDH

SDH (Synchronous Digital Hierarchy) is a standard technology for synchronous data transmission on optical media. Internationally, it is considered the equivalent of Synchronous Optical Network. To be more precise, it is the European equivalent of SONET, much like E1 is to T1. It carries all the bits from say, a call, within one transmission frame. It uses Synchronous Transport Modules (STM), like OCx with SONET. The data-rate can vary anywhere from STM-1 (155 Mbps) up to STM-64 (10 Gbps).

in



Modems of the additional devices necessary to

local area network requires cabling and network cards. The problem with these devices is that they all have limitations that prev ance communication. To increase our network bey puters, or over long distances, requires some additional hardware that will overcome the limitations of the cables, network cards, and media.

A mod evice that makes it possible to communicate long distances over standard telephone lines or cable. The name is derived from the words MO

Expanding a network requires an understanding make the connections. As we have already learned, connecting a few computers to form a

ent long distond a few com

em is a ddulate and

DEMo

Some of the basic functions of a modem are to:

• ital signals used by omputers into analog signals that can be telephone lines.

• rt the parallel digital dat

Modem e in both internal standard expansion card) and external (connected to a serial port and has its own power supply) versions.

Modem data at various spee . These speeds are measured as bits per second. Speeds will range from very slow speeds of 300 bps to 56,600 bps. FAX modems will send and receive data at speeds up to 14,400 bps. Originally modem speeds were measured in terms of Baud. The Baud rate equals the frequency in cycles per second that can be itted via telephone lines. With early modems, the Baud rate was equal to the bps. However, due to the physical characteristics of copper wire and the effects of transmitting signals over long distances, there is a limit of 2400 Baud. This limit cannot be exce ithout encountering sig l distortion. To overcome this and increase the speeds of data transmission via modems, designers learned how to place several signals within one cycle. Therefore, a given Baud rate could transmit data at 2, 4, 8, etc. times as fast as the Baud rate. With this change, the term Baud has disappeared and been replaced with bps. Today, modems have reached a new technology limit of 56,600 bps. Modems are classified by a “V” rating. The following is a list of common “V” ratings:

dulate.

Convert dig ctransmitted via

Conve a into serial digital data.

s are availabl (

s transmit ds

transm

eded w na

Standard bps Notes

V.22bis 2400 etimes included with ase of a computer.

An old standard. Somthe purch

V.32 9600 etimes included with the purchase of a computer. Som

V.32bis 14,400 High-speed version of the V.32 standard.



erbo 19,200 V.32t Not officially a standard yet. Will only communicate with another V.32terbo.

V.34 28,800 proved V.FastClass. Backwards patible with earlier V. modems.

Imcom

V.42 57,600 Backwards compatible with earlier V. ms – error correction standard. mode

V.90 56,600 odem standard – resolved competition for standard between US

standards.

56K m

Robotic X2 and Rockwell K56 Flex



AS) is through a Remote Access

Server, or RAS (pronounced RAZ) connection. You may be more familiar with the term thing. The puter is acting as a

server or gateway to a network and will receive calls via a modem from other computers. Dial-up networking is the client-side of the connection. For example, when you access

ia a modem connection) you are establishing a dial-up connection –you are the client. On the other hand, the server that you call (your Internet Service Provider) is providing a RAS connection to you – it is the

r you. The difference between a ndows 95/98) and a RAS server (such as Windows

Server 2003) is the number of inbound connections. A system running Windows XP or Windows 95/98 will allow only one inbound connection, while a true server like

n

Remote Access Computing (ROne of the most common forms of expanding a network

dial-up network (DUN). Actually, both of these terms mean the samedifference is how each computer is being utilized. With RAS, the com

your Internet connection from your computer at home (v

server that is providing the connection to the Internet fosimple computer (Windows XP or Wi

Wi dows Server 2003 will allow 256 inbound connections.

RAS Connection

Establishing a remote connection can be either between two computers or between a remote computer and a network. Let’s first look at connecting two computers. Any two

modems and telephone lines, or directly via COM ports and a cable.

ame room or building), all you each computer. A COM port is a 9-

pin male connector (it can be 25-pin but this is not as common as the 9-pin) on the back of the computer. The trick is that you cannot use just any cable with 9-pin female connectors. You must use a Null-Modem cable. This is a specially wired cable that actually replaces the modem. Since the two computers are directly connected, there will be no need to connect to telephone wires or dial a number, so this cable eliminates that part of a modem connection. Also, the COM port provides the parallel to serial data conversion that is necessary to complete a connection.

Both computers will have to run compatible software so that one will act as a server and the other as a client. There are many off-the-shelf software packages that will perform this type of communication. In addition, Windows XP has an feature called a direct cable connection. By running Network Connections Wizard and following the simple

Connecting Two Computers

computers can be connected, either via

When connecting two computers in close proximity (sneed to do is connect a cable between a COM port on



structions provided, you can connect any two Windows-based computers and share data ith only a cable connection.

inw

Direct Cable Connection

Making a RAS connection to a server is similar to a direct connection but, in this case, you will use a modem to establish the connection. The server you are contacting may be an individual computer or a server that provides access to a larger network. On the server side, the RAS software must be installed and running. With this in place, the server will answer the phone and allow the connection if you are an authorized user. On the client side, your computer will have to make the phone call and provide the necessary security authentication information to the server. Normally, the client computer will establish the connection via DUN software. Windows (95/98 and NT) has an accessory called Dial-Up Networking. From this accessory, you can set up the proper configuration for the connection and dial the appropriate number.

RAS Protocols

In order for any connection to work, both computers must be using the same protocol. RAS/DUN supports various connection protocols to ensure proper connections and security. These protocols are:

• SLIP (Single Line Interface Protocol)

• PPP (Point-to-Point Protocol)

• PPTP (Point-to-Point Tunneling Protocol)

• IPsec (Internet Protocol Security)

• L2TP (Layer Two Tunneling Protocol)

• SSL (Secure Socket Layer)

• TLS (Transport Layer Security)

• Kerberos (Greek mythology – three-headed canine who guards Hades’ gates)

• ICA (Independent Computing Architecture)

SLIP (Single Line Interface Protocol)

Serial Line Interface Protocol is a standard protocol for connections using TCP/IP (Transmission Control Protocol/Internet Protocol). This is a relatively old standard (1984), but is still in use with some systems. While this was the protocol of choice for a



long time, in today’s networks it has several disadvantages. Some of these disadvantages include:

• It requires a static IP address for each node.

• It transmits in text only.

• It supports only TCP/IP.

• It cannot encrypt logon information.

• It’s only supported by RAS clients.

PPP (Point-to-Point Protocol)

The Point-to-Point Protocol was designed as an upgraded protocol to SLIP. With the rapid growth of the Internet and remote communications, the limits of SLIP caused many problems. PPP was intended to overcome these limitations and is very common today. Some of these improvements include:

• Support for TCP/IP, IPX, NetBEUI, AppleTalk, and DECnet.

• It supports encrypted passwords.

• It provides data compression and error control.

• It provides security.

PPTP (Point-to-Point Tunneling Protocol)

Point-to-Point Tunneling Protocol (PPTP) provides for a secure encrypted tunnel for communication through the Internet. This is accomplished by encapsulating one protocol with another protocol, such that only the sender and the receiver can accurately interpret the data that is being sent. Many organizations are using tunnels, created by PPTP and other tunneling protocols, as a less explensive alternative to costly leased lines.

• Secure transmission over TCP/IP networks.

• It enables highly private network links over the public Internet.

• Encrypted Connections.

• VPN (Virtual Private Networks).

• RAS and Security.

IPsec

IPsec (Internet Protocol Security) is a framework of open standards for security at the Network layer of the OSI model. It is designed to protect IP packets as well as to provide defense against network attacks. It can be used in conjunction with VPNs (Virtual Private



Networks) and remote access for users who need access to resources on a private eaning that the computers, both

transmission. It is transparent to

e

d is g

s

Directory use this type of security by default, as does Novell Directory Services (NDS). .

ICA (Independent Computing Arc

ive, stem (such as Windows CE), limited RAM, and a processor in

the range of 200 MHz to 300 MHz. ICA can be used with Windows, UNIX, Linux, and Macintosh m

network. It is based on an end-to-end security model, msending and receiving, are the ones aware of the IPsec the user.

IPsec allows for either ESP (Encapsulating Security Payload) or AH (Authentication Header). ESP, which is the highest security method, authenticates the sender of data and encrypts the data as well. AH only authenticates the user. Kerberos V5, certificates (likX.509) and preshared keys can be used for authentication in conjunction with IPsec.

L2TP

Layer Two Tunneling Protocol (L2TP) is the latest version of the tunneling protocol. Unlike PPTP, it does not require IP connectivity. It combines Cisco’s Layer 2 Forwarding (L2F) with PPTP. It functions at the Data-link layer of the OSI model anused in conjunction with VPNs. L2TP offers many advantages over PPTP, most relatinto higher security.

SSL

The Secure Sockets Layer (SSL) is a protocol for addressing the security of an Internet transmission between a client and a server. It uses a key to encrypt the data, usually a user’s credit card number. It is included in both Microsoft’s Internet Explorer and Netscape’s Navigator and it is a complimentary addition to HTTPS, discussed here in thenext chapter.

TLS

TLS (Transport Layer Security) is the evolution of SSL. It can work with SSL and uses Triple DES encryption (three 56-bit keys).

Kerberos

Kerberos is a secure method for authenticating a request for a service in a computer network. It allows a user to request an encrypted ticket, or virtual proof-of-identity cardso the user can request a service from a server. It does not provide authorization; it only establishes the user’s identity.. Windows 2000 and Windows Server 2003 Active

hitecture)

ICA is a remote connection established using Citrix software (like WinFrame or MetaFrame) and a thin client environment. Thin clients are computers with no hard dra bare-bones operating sy

co puters.



In addition p g of information, RAS provides several layers of security. As with all security measures, you must implement or enable them during configurati o security functions:

Au in

The server can create and maintain an audit trail of all connections. This audit can include who signed on and when they signed on.

Callback Security

One method of providing both security and cost control is to require the server to callback anyone that attempts to logon. By requiring RAS to call back to the client that is requesting a connection, you can restrict the numbers that RAS will call, therefore ensuring that the connection is legitimate. This feature can also be used to ensure long distance charges are charged to the company rather than the caller. This is a great benefit for those who travel for business and need access to the network.

Security Host (Bastion Host)

A security host or bastion host is a separate server that works between the RAS server and the client. This provides for additional authentication, and thus more security.

Installing and Configuring RAS

Installing RAS on a server is dependent on the network operating system installed on the server. Before installation, you will have to collect all the information from your operating system supplier to ensure that you have everything necessary. In addition, you will need to collect data on the type of connection you intend to make and the specifics of the computer hardware and network. At a minimum you will need to know the following:

• Your modem specifications including having the appropriate drivers for your network and/or computer operating system.

• The type of communication port you intend to configure.

• Are there any client protocols that will have to be enabled?

• What are the security requirements of the connection/network? Troubleshooting a RAS setup

While not usually complicated, installing RAS can be frustrating. If it does not work the first time, you will have to carefully go through all the configuration parameters and check every one. All it takes is one number or check mark out of place to prevent the connection from working properly. Be sure to check everything including the RAS configuration, the modem configuration, and any other software that might use the modem. If another software package has “control” of the modem, your new RAS system may not be able to gain access.

to roviding remote sharin

on f the RAS server. Here is a summary of RAS

dit g



Limitations of RAS

ot always the solution for every network. As a networking

e connection. The latest Microsoft server operating indows Server 2003 have wizards that

uch simpler.

As good as RAS is, it is nprofessional, you will need to understand both its strengths and weaknesses. You shouldconsider RAS when your bandwidth is less than 128 Kbps, you want to keep the costs down, and you don’t need a fulltimsystems such as Windows 2000 Server and Wmake installing an RAS server m



KEDef .

YWORDS Exercise ine each of the following keywords. Hint: There’s a glossary in the back of this book

Keyword Definition

Analog Signal

Bridge

Carrier

Concentrator

CSU/DSU

Digital Signal

DUN

Frame Relay

Gateway

Hubs

ICA

Ipsec

ISDN

Kerberos

L2TP

MAU

PPP

PPTP

RAS

Repeater

Router

SDH



Keyword Definition

SLIP

SMAU

SONET

SSL

T1

VLAN

X.25



hapter 7 etween a hub and a MAU?

3. Define a repeater, a bridge, a router, and a gateway.

7. What are the two components of remote network accessing?

e three RAS protocols.

10. Describe the difference between BAUD and bps.

Review Questions C1. What is the difference b

2. What is the difference between an active hub and a passive hub?

4. What is analog communication?

5. A form of digital line that is capable of 1.544 Mbps transmissions is called?

6. Name three advanced WAN environments.

8. Nam

9. Name four forms of RAS security.



Chapter 8 – TCP/IP Essentials



Introduction to TCP/IP

ayer protocol (based on the OSI Model). TCP is built on top of IP (Internet d is usually seen in the combination, TCP/IP.

s

ternet. This is the most common l suite with which a networking professional works. It is important for the

TCP/IP is an internet (between network) protocol. It is also used with Ethernet networks, intranets, and the Internet. Transmission Control Protocol (TCP) is the most common Transport lProtocol), an

TCP/IP was developed by the Department of Defense agency (DARPA) in the 1960s apart of a military research project. TCP/IP was designed to accommodate a large internetworking environment comprising several different types of computers. From this beginning, it has evolved into the protocol of the Inprotoconetworking professional to know that TCP/IP is used on the Internet and that it can be used with almost any network operating system.

RFC (Request For Comments)

A series of documents called RFCs (Request For Comments) serve as the standards thatwere used in the development of TCP/IP. Although RFCs are not true standards (they are documents that describe work in progress), some are considered to be Internet standards. These standards, as well as Internet standards, are the responsibility of the IAB (Internet Activities Board).

The TCP/IP protocol suite includes a number of protocols, such as SMTP, SNMP, and FTP, which will be discussed later in the chapter. TCP/IP is a routable protocol that provides full duplex connections. Full duplex means that data can travel in both directions at once. Its popularity is largely attributed to the fact that it is not owned by a specific vendor. TCP/IP is an open protocol and is considered to be an industry standard. Also, these protocols were available on UNIX early on, and were even built into the Berkeley Standard Distribution, known as BSD UNIX. TCP/IP is now the standard on allversions of UNIX, and is in fact, the recognized standard for internetworking altogether.

The TCP/IP suite consists of four layers. Each layer maps to one or more layers of the OSI model. The four layers are: Application, Transport, Internet and Network Interface.



TCP/IP and OSI

The four layers that make up TCP/IP provide a guideline for this model. There are actually five protocols that work within these layers to provide network connections. These five protocols are:

• TCP- Transmission Control Protocol

• UDP – User Datagram Protocol

• IP – Internet Protocol

• ICMP – Internet Control Message Protocol

• ARP – Address Resolution Protocol





TCP

Transmission Control Protocol (TCP) functions at the Transport Layer of the OSI Model. Its job is to ensure tha sferre from noth r reaches its destination intact. TCP b ta in aller units of ment gram . It th ation to its destination,

data. This data exchange can be verified at various checkpoints.

ich data travels are called ports. A port is a virtual outlet that can be ork device. Port numbers are generally predetermined and

at is running on a machine.

TCP/IP Protocols As a network technician, and for the Network+ exam, you will not have to be an expert on the workings of TCP/IP. However, you will need to know the various protocols and how they relate to the OSI model.

The Top Five TCP/IP Protocols

As mentioned earlier, there are five major protocols used within TCP/IP. Let’s take a look at them.

t data tran d one computer to a ereaks da to tiny chunks, called packets, or into even sm

measure called data s en routes the informand reassembles theShould lost or corrupted packets be detected, they can be retransmitted in a timely manner.

TCP operates by first establishing a connection-oriented session through the use of ports and sockets. It will then use the concept of sliding windows and acknowledgements to ensure fast and accurate data transmission. Let’s take a look at how this works.

On a TCP/IP network, the origination point and destination point of the computers between whopened on a netwcorrespond to a specific service th

Port numbers for some protocols are better known than others. The following list provides a few examples:

For: Use Port

FTP 21

TELNET 23

SMTP 25

HTTP 80

POP3 110



d with the range from 1024 through

FTP, HTTP, Telnet, etc., you are automatically connected to the

he terms, “port” and “socket” are a socket. The port number

identifies the appl ted w a. A ombination of an IP address and a p

-Or nica hat s bet ines unication is called a session and is

used to provide guaranteed delivery between the two

owledgem to en re the reliability of the data being transmitted. as a

Sliding windows are ease of data transfer. This allows a receiving machine to collect p r until all packets in a speci re rec machines have a sending and receiving window to buffer the data flow. Transmission speed is increased by sending a window of at a ut having to get an acknowledgment back for each packet. Both machines keep track of the data so

does it check for errors. UDP packets are delivered through ports and sockets and do not and is often

used when transmitting streaming audio or video.

m its origination point to its destination point. IP is connectionless, meaning that it establishes an end-to-end connection and starts transmitting without

s e IP

tocol number, and a

The sending computer’s address is called the source port number, and the receiving computer’s address is called the destination port number. The addresses, or port numbers, consist of a unique 16-bit numeric address ranging from 0 to 65,535. The well-known ports are associated with the range of possible port numbers from 0 through 1023. The registered ports are associate49151. The private or dynamic ports are associated with the range from 49152 through 65535. When you open a dial-up connection to the Internet, and specify acertain protocol, i.e. correct port for that particular data type. Although toften used interchangeably, a port is different from

ication associaort number.

ith the dat socket is the c

Connection iented Commu tion means t direct communication iestablished ween two mach . This comm

machines.

Ackn ents are used suFor each packet sent, an acknowledgement of receipt is returned. Think of itreturn receipt like the one you get from the Post Office when you want to be surethat a package has been delivered.

used to incrackets out

the speedof order and hold them in a buffe

fied group a eived. Both

information time witho

that any packets not received can be resent.

UDP

User Datagram Protocol (UDP) is a connectionless protocol residing on the Transport layer of the OSI Model. UDP transports data, but does not acknowledge delivery, nor

require the opening of a session. The advantage of UDP over TCP is speed

IP

Internet Protocol (IP) is the Network layer part of TCP/IP, which is responsible for moving the data fro

swapping control information. TCP tells IP that the data has arrived at its destination. If the transmission has not been successful, TCP will retransmit the data. IP merely routethe data, inserting its own header into the datagram when it is received from TCP. Thheader consists of the source and destination addresses, the pro



checksum The IP hearoute the datagram.

Note: A c on data by the sending

. der is necessary so that gateways are able to determine where to

hecksum is simply a calculation that is performed computer. To be m erived from this ore specific, the checksum is the answer that is dcalculation. When the data arrives at the destination computer, the receiving computer performs the calculation. If the checksum is the same, the data is assumed to have arrived intact.

The following are key elements of IP:

Addressing – provides the address of both the sending and receiving machines.

derlying t size for transport.

Routeability – provides routing information from one network to another.

Time to Live – provides TTL data. This defines the number of hops a packet can

e for keeping track of the mapping of IP aintains an ARP cache.

th which it is communicating. The contents of a cache can be displayed by using the ARP.exe command in Windows or the /sbin/arp

her TCP/IP Protocols

In addition to the top five, TCP/IP uses several other protocols:

POP3

s the client computer to retrieve E-mail from a POP3 server using a temporary connection.

is also a protocol for accessing email from your local server. Your Internet server holds your incoming email until users logon and

ed than POP3 because you can use folders and mailboxes on the server, run searches, or access multiple mail servers.

Broadcast – provides broadcast addressing within a network segment.

Fragmenting and Reassembly – if data packets are too large for the unnetwork, it will be broken down into a manageable packe

make before it is discarded.

ICMP

Internet Control Message Protocol is part of the Internet layer. It is responsible for errors and messages regarding delivery of IP datagrams.

ARP

The Address Resolution Protocol is responsibladdresses to physical addresses. Each device on the network mThis cache contains a list of all the devices wi

command under UNIX.

Ot

Post Office Protocol Version 3 (POP3) allow

IMAP4

Internet Message Access Protocol (IMAP)

download it. It is more advanc



t, which

Send

ges dual computers) on an IP network. SNMP is not limited to TCP/IP.

FTP

File Transfer Protocol (FTP) is a client-server protocol that allows a user to transfer files from one computer to another over a TCP/IP network. The user accesses a special directory hierarchy containing public access files, by typing in a user name, or the word “anonymous.” The password is the user’s E-mail address. Files may then be uploaded or downloaded between the computers.

HTTP

HyperText Transfer Protocol (HTTP) is a client-server protocol that is used on the World Wide Web (www) to access HTML documents, such as web pages.

HTTPS

HTTPS (Secure Hypertext Transfer Protocol) is a Web protocol that encrypts and decrypts, using SSL as a sub layer underneath HTTP, allowing access to a secure Web server. It uses port 443, the secure SSL port instead of port 80, the HTTP port. HTTPS, as well as SSL, allow for the use of X.509 digital certificates for authentication of a user.

POP and IMAP allow a client to pull their mail from a server. Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail between points on the Interneis what you use when you send out mail. SMTP is server to server, whereas POP or IMAP are client to server.

SMTP

Simple Mail Transfer Protocol (SMTP) is a server-to-server protocol that acts under the control of the message transport system. SMTP is used to transfer E-mail between computers, usually over the Internet. An easy way to think of it is SMTP stands for “Mail To People.”

SNMP

Simple Network Management Protocol (SNMP) is the Internet protocol that mananodes (indivi





Naming Systems aming conventions and addressing is a large part of networking and TCP/IP. emem e working in two worlds, the computer world of numbers and our world

of user-friendly names. Understanding the difference between these two worlds and how

Domain Name S es to IP addresses over a TCP/IP network. The network administrator defines and configures the DNS settings usi hone directory. The network administrator need on y remember the host and domain names. A domain name server is a computer that "r rs" the user-friendly names of the other computers and their IP address numbers. For example, the domain bigcompany.com may have an IP addres er the user-friendly name while the domain name server remembers the numbers used by the

a

such r

NR ber, we ar

to work in both of them is an important part of networking.

DNS

ervice (DNS) is a network service that translates hostnam

ng a standardized lookup table. DNS functions like a telepl

emembe

s of 192.49.238.33. This allows users to simply rememb

network computers.

A domain is a group of computers that share a common general purpose, such as government, education, commerce, or interest. Internet domains are established in hierarchical order. A Fully Qualified Domain Name (FQDN) consists of a hostname and a domain name. The Internet Network Information Center (InterNIC, also known as Network Solutions) controls the top-level domains. These domains require suffixesas .com for businesses or .edu for educational institutions. It is also common practice fovarious companies to register domain names for you.



.com aniza

.net ackbo rnet.)

.edu Educational Institutions

.org

Government Organizations

il rnm ions

.biz ses

.pro ssional

.info es

.xx

For instance, Big Company Inc. in Italy ight be http://www.Bigcompany.com.it

The following table lists some Internet domains:

Commercial Org tions

Networks (The b ne of the Inte

Non-profit Organizations

.gov Non-military

.m Military Gove

Busines

ent Organizat

Profe

Information servic

Two Letter Country Code

m

stration fees.

WINS

In a Windo -resolve NetBIO er names to their IP addresses. This is a dynamic service and

e WINS server each time it logs on to the

nsibility for error-checking up to the application.

e)

or in Australia www.Bigcompany.com.au. Also, .tv is gaining in popularity. Tuvalu is a small country, which receives financial benefit from the regi

ws based network, the Windows Internet Name Service (WINS) is used to S comput

requires that the workstation register with thnetwork.

NETBIOS

NetBIOS defines a session-level interface and a session management/data transport protocol so computers can converse in session mode or send messages without connection in datagram mode, leaving the respo

A NetBIOS name is a unique 16-byte address (only 15 can be used for the actual namused to identify a NetBIOS resource on a network. There are four node types: B-node (broadcast), P-node (peer-peer), M-node (mixed – B and P) and H-node (hybrid – P and B).



a static IP address. This means that it is permanently assigned. It would

ssigning IP addresses is like assigning telephone numbers, sooner or later we will run bers. In smaller isolated networks, IP address assignment is not a big problem

and eac s e of addresses required increases, with a number shortage. To resolve this, IP addresses can be dynamically assigned. That is, assigned on an “as needed” basis. Each host will lease an address only for the period of time required. When not needed, the address can be leased to another host. T ccom , you will need to use Dynamic Host Control Protocol (DHCP). Upon logon a DHCP server will provide a client with an IP address, subnet mask, and a default gateway if needed.

Notice esses are leased. This means that they will expire af ecific amount of time. This is to prevent one user from monopolizing the connection. A lease can be the term of the lease is at 50%, the client will send a request for renewal. If the demand for connections is low (there are spaces available), the lease will be rene d, the client will attempt to contact the DHCP server that issued it the IP address directly about every 5 n es 87.5% of the lease, at which time the client will broadc a reqfrom a server. If all addresses are being used or a DHCP server does not res l expire and the address will be assign anoth er. In this case, th l have to wait for an opening b re getting another lease and a new IP

BOOT

BOOTP (Bootstrap Protocol) is a protocol that is used by diskless workstations to obtain their IP addresses (as well as the server’s address and it fault gateway) from a BOOTP server. BOOTP was the foundation of the Dynamic Host Configuration Protocol (DHCP).

HOSTS file

HOSTS file is a static text file that maps host names to IP. It predates DNS. It must be manually created and changed.

LMHOSTS file

LMHOSTS is static text file that are used to look up and resolve NetBIOS names and IP addresses. It predates WINS and is rarely used today. It must be manually created andchanged.

IP Gateway

A gateway is used to connect two networks with dissimilar protocols. For example, it could connect a LAN to the Internet. In order for a gateway to work with the Internet, itmust be assignedbe difficult to find if it were constantly changing.

DHCP

Aout of num

h workstation or device can have a static addreyou will sooner or later com

s. However, as the up

number

o a plish this

that the IP addr ter a sp

renewed. When

wed without interruption. If not reneweminutes u

uest to obtain an address til it reach

ast ny available DHCPpond, the lease wil ed to er use original user wil address.

efo

P

s de



etwork Connection Utilities NAT

NAT (Network Address Translation) is the translation of an IP address used within an organization internally (private IP address) to an IP seen by the Internet (public IP address). It allows for use of one public IP address for m T also acts as a type of firewall, since it keeps the private IP addresses hidden from the outside world. Actually, a NAT is just a device or program that translates one set of IP addresses to another set of IP addresses, but it is most often used between a private network and the networks public address or addresses.

IP Prox

Earlier, we talked about the client/server relationship in terms of the roles of various sers and servers. In the case of a proxy server, it serves many clients through only one

connection. The user is connecting to the Internet via a secondary source, i.e. the proxy the

k or to the Internet on behalf of the client. The proxy server may function in the role of the server or

N

any private IP addresses. NA

y Servers

u

server. Compare this to a “he said-she said” scenario where an intermediary delivers message between two parties who do not speak directly to each other. The proxy server isa liaison between the two parties, who think they are communicating directly with one another. The proxy server is actually making a connection to another networ

the client, depending on the direction in which the communication is traveling at any given time.

Proxy Server

ICS

ICS allows comInternet. It contains DHCP, NAT, and DNS. ICS allows multiple users to fully utilize that connection by conjunction w

puters within a network, like a LAN, to share a single connection to the

performing different tasks at the same time. It can also work in ith Routing and Remote access.





CP/IP Addressing IPv4

Enough talk about IP address names, let’s now take a look at IP address numbers. Network computers require a unique IP address so that the other computers on the network can identify them and be able to communicate with them. This IP address is a 32-bit bin binary number 6 (4.2 billion) different numbers. Imagine how difficult it would be to have to remember a combination of 32 1s and 0s for each address. at is easy for a computer, it is not easy

To simpl e broken d r octets. An octet is a group of eight binary digits and a period or “dot” separates these octets. Each of these octets represent e result is ed decimal number. A basic knowledg system is required to understand network addressing:

The 32-b 100100111 000010 Broken down into four octets: 00100001.00100111.00001000.11000010 Each octet represents a number between 0-256: 1st octet: 0 0 1 0 0 0 0 1 ------------- ----------- 16 8 2 1

Adding the values assigned to the “1” positions gives us a value of 33 for the first octet.

1 0 0 1 1 1

4 32 16 8 4 2 1

The value of the 3 octet in our example is 8.

an

he nal have a basic understanding of these classes.

T

ary number. A 32-bit can represent (232) or 4,294,967,29

Although thfor us.

ify these addresses, they ar own into fou

s a number from 0-256. The of the binary numbering

called a dott

it binary number: 0010000 0000100011

-------------------------128 64 32

---------------- 4

2nd octet: 0 0 ----------------------------------------------------------------- 128 64 32 16 8 4 2 1

The value of the 2nd octet is 39.

3rd octet: 0 0 0 0 1 0 0 0 ----------------------------------------------------------------- 128 6

rd

4th octet: 1 1 0 0 0 0 1 0 ------------------------------------------------------------------ 128 64 32 16 8 4 2 1

And finally the value of our 4th octet is 194.

So the dotted decimal address of our example is 33.39.8.194.

If a network is internal and does not access the Internet, the administrator may assign IP address to each computer (as long as the number is unique). Internet IP addresses, however, are assigned by the Internet Corporation for Assigned Names and Numbers (ICANN) and these IP addresses are further divided into classes. It is important that tnetworking professio



Addresses

he dot ur on t(s) on the left repre e Network ID (Network ID) and the octet(s) on the rig esents

e Hos D). The class ddress determines which octets identify the ID. Within classes, the on the

ft is a f the Network always part of the ost ID ctets in the ce er assigned to the Network ID or the ost ID g on the assig ork is divided into classes. The class can e determined by the value of the first octet. There are five common classes: A through . For the Network+ exam, you should pay special attention the Classes A, B and C.

Class A 01-126 (leading bit = 0)

Class B 128-191 (leading bit = 1)

Class C 192-223 (leading bits =11)

Class A Addresses

If the network applying for Internet IP addresses is extremely large, only the first octet is used for the Network ID and all three remaining octets identify the host (Host ID). (A host may be any device on the network.) The first octet in a Class A address is always a number between 1 and 126. The example we used to define a dotted decimal address of 33.39.8.194 would be an example of a Class A address. The first octet (33) would identify the network (Network ID) and the rest of the octets would identify the host (Host ID) 39.8.194. The leading bit in the binary representation of a Class A address is always 0 (00000000).

Class B Addresses

This class is assigned to medium sized networks. The first two octets identify the network (Network ID) and the last two octets identify the host (Host ID). The first octet in a Class B address is always a number between 128 and 191. An example of a Class B IP address would be 129.39.8.194. In this case 129.39 would be the Network ID and 8.194 would be the Host ID. The leading bit in the binary representation of a Class B address is always 1 (10000000).

Class C Addresses These are the most common and are used for smaller networks. In this class the first three octets are used for the Network ID and only the last octet is used for the Host ID. The first octet of a Class C address is always a number between 192-223. An example of a Class C IP address would be 193.39.8.194 where the Network ID would be 193.39.8 and the Host ID would be 194. The leading bits in the binary representation of a Class C address are always 11 (11000000). Class D and Class E Addresses

Class D cannot be used for networks (multicast) and Class E IP addresses are reserved for future use.

IP

T ted decimal number is f ther broken down into two comp ents. The octesents th

t ID (Host Iht repr

th of the IP aNetwork ID and which octets identify the Hostle

first octet lways part o ID and the last octet on the right is

HH

. The two o

. Dependinnter can be eithnment, the netw

bE



Since a Class A Network ID uses the remaining three octets to assign numbers for the ID numbers. Likewise, Class B uses two

Host ID, there are 16,777,214 possible Host octets for the Network ID and two octets for the Host ID, there are only 65,534 possible Host ID numbers. Class C uses three octets for the Network ID and only one for the Host ID, so there are only 254 addresses available for hosts. You can see that Class A has the largest number of hosts, with the least number of Network IDs. Also, Class C has a largenumber of Network IDs and only a few Host IDs.

Note: The existing shortage of addresses has made it impossible to obtain a Class A address for a long time.

Some IP Addresses are reserved for special purposes:

If: Network ID Host ID IP Address

All Zeros This Network This Node Default Route for RIP

All Ones All Networks All Nodes Broadcast

127 Local Node

It is important for the networking professional to be able to identify whether an IP t

CLASS A 1 - 126

address is a Class A, B or C address. Use the following table to memorize the differenclasses:

CLASS B 128 - 191

CLASS C 192 - 223

In addition, there are some IP addresses that are reserved for special purposes:

es that begin with 127 and 224 through 255 are used for testing purposes and for etwork

to send a test packet to itself without generating network traffic. This is the loopback address, specifically 127.0.0.1)

Class A - used by very large networks. All in use and no longer available.

Class C - used for smaller networks that do not exceed 254 hosts. Class C IP addresses are still available.

As we mentioned earlier, if a network is going to be connected to the Internet, you must petition the official Internet authorities for the assignment of a network address. This organization is called InterNIC (Internet Network Information Center), and they are responsible for the assignment and regulation of IP addresses.

Addressmulticasting and are not available for normal host addresses. (For example, the NID of 127 designates the local node and allows that node

Class B - used for medium-sized networks. Class B IP addresses are all in use and no longer available.



Contact InterNIC at:

Network Solutions InterNIC Registration Services 505 Huntmar Park Drive Herndon, VA 22070 You can also E-mail to [email protected].

IPv6 (IP Next Generation)

IPv6 (IP Next Generation) is the latest IP technology. It uses 128-bit addressing, as compared to IPv4, which only uses 32-bit addressing. It does, however, demand high bandwidth. The benefits of IPv6 include improved scalability, as well as ease of configuration and security built right in.

IPv6 uses hexadecimal numbers (0 to 9, then A to F) instead of decimal because of the length of the new addressing scheme. It uses eight 16-bit pieces with colons as separators as opposed to the full stops used in IPv4. An example of IPv6 is as follows:

AAAA:BBBB:0000:0000:0000:0081:FFFF:DDDD

A shorthand version of the previous IPv6 address:

AAAA:BBBB:0:0:0:81:FFFF:DDDD

Leading zeros can be taken out, but at least one must be left in each 16-bit field. You can compact multiple fields of zero beyond the previous example. This happens to supercede the rule about one zero having to be left in a field. A double colon can be used to represent multiple contiguous fields of zeros.

For example, the following address

0000:0000:0000:0000:0000:0000:0000:0000

0000:0000:0000:0000:0000:0000:0000:0005

can be represented in their compacted form by

::

::5

You cannot, however, use the double colon more than once in an IPv6 address. It would make it unclear as to what was represented.

Rather than having “classes” like IPv4, IPv6 uses format prefixes (FP), which are variable-length fields that comprise the high-order bits, to define the address type. The address types are Unicast, Anycast, and Multicast. Unicast is an address for a single host. Here is an example of a Unicast address:

1070:0:0:0:7:777:300F:754B



Unicast addresses can be broken down further into four sub-groups: Global aggregatable local address and IPv4-compatible address. An

affic to a domain. Link-Local addresses use the FE80::/10 prefix and are used by hosts n a local link. Finally, IPv4-compatible IPv6 addresses have zeros in the section beyond

the 32-bit address (0:0 :C:D or ::A:B:C:D)

Anycast is an address for a set of in rfaces that typically belong to different hosts and is delivered to the closest one. Multicast, which replaces broadcast, is an address for a group of hosts within a scope and has a FF00::/8 prefix.

The Loopback address in IPv6 is 0:0:0:0:0:0:0:1 or ::1, just like 127.0.0.1 with IPv4.

All r a multitude of IP address possibilities for the future of netw

address, Site-local address, Link-aggregatable global address uses a fixed prefix of 2000::/3. A Site-local address uses the prefix FEC0::/10 and can be regarded as private addresses, since they can be used to limit tro

normal IPv4 :0:0:0:0:A:B

te

in all, IPv6 allows foorking.



Subnetting Subnetting is the process of creating more than one private network from one public network address by customizing your subnet mask. For example, a large university may hav ead over several uildings and perhaps remote campuses. By using subnets, you can reduce the overall network traffic. In this example, all the traffic within a bu us will be kept lo pt when it needs to go to another subnet. Sinc er connects each subne affic that is not local will pass through.

By using a concept called anding, a router can determine which addresses are local and which addresses are for other subnets within the network. Anding is the binary addition that the router uses to make this determination.

Before looking at anding, lets look at subnet masks. A subnet mask is an IP address (dot number) in which all ones represent the network portion of the IP address and all zeros represent the host portion of the IP address. For example:

11111111.11111111.00000000.00000000

or

255.255.0.0

In regard to classful addressing , a subnet mask can be 255.0.0.0 (Class A), 255.255.0.0 (Class B), or 225.255.255.0 (Class C). The number of 0s determines the maximum number of available hosts within the sub-network.

Default Subnet Masks

e a network spr b

ilding or camp cally excee a rout t, only the tr

ted-decimal

255.0.0.0 Class A (16,777,216 hosts)

255.255.0.0 Class B (65,534 hosts)

255.255.255.0 Class C (254 hosts)

Note: You cannot use IP addresses with all 1s or all 0s. You can use a subnet mask that does not completely use all the bits in an octet. You must however, have all 1s to the left and all 0s to the right. Subnet masks with full octets (255) are the default subnet mask.

The purpose of a subnet mask is to determine the network portion of the IP address, separating it from the host portion of the address. This is done with binary addition (anding), which uses a certain logic to determine the network portion of the address. If you “and” the IP address to the subnet mask, the results will be the actual network portion of that IP address (not necessarily the default network portion determined by its class).



Remember, for binary addition:

0 + 0 = 0

net mask of 255.224.0.0.

9.8.194)

11111111.11100000.00000000.00000000 (255.224.0.0)

equals

00100001.00100000.00000000.00000000 (33.32.0.0)

d through leaving only the digits for the network portion or 33.32.0.0, while the Host ID 0.7.8.194 is determined by the zeros in the subnet mask. By using this method, a router can determine if a message is for a

network or for a machine on a remote segment. Any local addresses will not pass through, thus reducing the traffic on the rest of the network. It is common in TCP/IP to omit the trailing octets in the Network ID and the leading octets in

nd octet, it recognizes the first 11 bits as the network portion of this address. Those 11 bits equal a network portion of 33.32. The remaining 21 bits in the IP address is the host portion This equals 7.8.194.

the subnet sk does not take up a com

addresses and subnet masks:

1 + 1 = 1 1 + 0 = 0

Now, using our previous example of 33.39.8.194, let’s and it to the sub

00100001.00100111.00001000.11000010 (33.3

Noticing that all the places that have ones, an

destination on the local

the Host ID. Therefore in our example the Network ID is 33.32 and the Host ID is 7.8.194. Since the subnet mask only goes 3 bits into the seco

The network and host portions do not break down neatly into octets sincema plete second octet. The following tables summarize IP



efault Subnet Mask and Network Classes

Class IP Address Default Subnet Mask

D

A 001.a.b.c to 126.a.b.c 255.0.0.0

B 128.a.b.c to 191.a.b.c 255.255.0.0

C 192.a.b.c to 223.a.b.c 255.255.255.0

Maximum Networks and Hosts per Class

Class Default Subnet Mask

Number of Networks

Number of Hosts

A 255.0.0.0 126 16,777,216

B 255.255.0.0 16,384 65,534

C 255.255.255.0 2,097,152 254

How to Subdivide a Network

The process of subdividing a network into logical units is called subnetting or subnetworking. There are several reasons to divide a network in this manner.

• Connect physically remote local networks.

• Connect a mix of network technologies (Ethernet and Token Ring).

• Allows an unlimited number of hosts to communicate.

• Reduce network traffic by limiting broadcast and local traffic to a single segment.

There are steps to follow when subnetting:

Determine the number of Network IDs required.

A unique network ID is required for each subnet and each wide area network. Be sure to include some room for growth of the network.

Determine the number of Host IDs per subnet.

A unique host ID is required for each TCP/IP computer network interface card, each TCP/IP printer network interface and each router interface on each subnet. If a router is connected to two subnets, it will require an address for each subnet.



Define the Subnet Mask

The goal is to define one subnet mask for the entire internetwork that gives the desired number of subnets and allows enough hosts per subnet. To begin this process, you will need to start with the network ID supplied by InterNIC. We will use an InterNIC ID of 191.36. First, we will notice that this is a Class B network and therefore the default subnet mask will be 255.255.0.0. With this number, we have one network with approximately 65,000 hosts. As we begin to subnet, we are increasing the number of network addresses that we can use and decreasing the number of host. We do this by using bits from the next octet or octets as part of our network addresses that we assign. You should remember the formula 2n-2 where n is the number of bits borrowed. We use this formula to determine the number of subnets that will be created by borrowing bits from the hosts.

The following table shows the subnet mask created by borrowing bits and how it will affect our network.

Class B Subnet Mask (2 to 14 bits borrowed) Bits Subnets Hosts

255.255.192.0 2 0 N/A

255.255.224.0 3 6 8190

255.255.240.0 4 14 4096

255.255.248.0 5 30 2046

255.255.252.0 6 62 1022

255.255.254.0 7 126 510

255.255.255.0 8 254 254

255.255.255.128 9 510 126

255.255.255.192 10 1022 62

255.255.255.224 11 2046 30

255.255.255.240 12 4096 14

255.255.255.248 13 8190 6

255.255.255.252 14 16,382 2



Class C Subnet Mask (2 to 6 bits borrowed) Bits Subnets Hosts

255.255.255.192 2 0 N/A

255.255.255.224 3 6 30

255.255.255.240 4 14 14

255.255.255.248 5 30 6

255.255.255.252 6 62 2

To make this easy, you can use the scientific calculator supplied with any Windows operati his example, lets keep our network ID of 191.36 as assigned to us by Inte y know that the first two octets will be 10111111 00100100 from this ID bits of the third octet do we need to use?

After e e that we will need 14 subnets to meet ou dd 4 more for future expansions, giving us a total requirement of 18. Now we get out our Windows calculator. Make sure that it is in s w (that’s the big calculator).

ng system. For trNIC. We alread, the question is how many

xamining our network requirements, we determinr current needs. Just to be on the safe side, let’s a

cientific vie

1. Make sure that the decimal mode (Dec) is selected.

2. Enter the value of 18.

3. Change the mode to binary (Bin). The number 18 will now be in binary (10010).



4. Count the number of binary digits (5). This will be the number of birequired for the third octet.

This will actually allow us up to 30 subnets with 2,000 hosts each. Also notice that hawe chosen 14 (no allowance fo

ts

d r growth), our answer would have been to use 4 bits and

we would have been limited to a maximum of 14 subnets. Had we needed to add a new ad to reconfigure the entire network, instead of selecting the next

subnet on our list. For this example, the subnet mask would be 255.255.248.0.

One you determine the number of subnets required and the subnet mask, you can determine the available Network IDs. To keep things simple, let’s look at the subnets for the subnet mask of 255.255.224.0 and the network address of 192.36. The following table shows the six subnets created when using the three bits of the third octet:

subnet, we would have h

Determine the Network IDs



Subnets (Subnet Mask 11111111 11111111 111)

Binary Network ID Dotted-decimal ID

11000000 00100100 192.36 (overall network address)

11000000 00100100 001 192.36.32

11000000 00100100 010 192.36.64

11000000 00100100 011 192.36.96

11000000 00100100 100 192.36.128

11000000 00100100 101 192.36.160

11000000 00100100 110 192.36.192

Determine the Host IDs

The host ID can be assigned as any number starting with the last digit of the forth octet (00000001), up to and including the remaining digits not used with the subnet ID. In dotted-decimal format, this means that the number starts with .001 in the last octet, and

one less than the subnet ID of the next subnet. The only restrictions are

ork, or one that is located on a remote network. For example, on a Class A network the default subnet mask would be 255.0.0.0. This indicates that the Network ID is located in the first octet of the network address. A Class B network default subnet mask would be 255.255.0.0 and the default Class C subnet mask would be 255.255.255.0, indicating that the Network ID is contained in the first two or three octets respectively. The zeros indicate the location of the Host ID.

The sending computer checks the octets of the destination address against its own to determine if the destination computer is on the local network or a remote network. (If the sending computer and the destination computer have the same subnet mask, they are on the same network. If it is different, the sending computer will send the message to a router for delivery.)

continues up tothat you cannot use .000 or .255; these are reserved for broadcast addresses.

Summary of Subnets

Subnet masks are used on TCP/IP networks to determine whether a message is for a computer that resides on the local netw



NETWORK CLASS DEFAULT SUBNET MASK CLASS ID

CLASS A 255.0.0.0 1 - 126

CLASS B 255.255.0.0 128 - 191

CLASS C 255.255.255.0 192 - 223



s r

ve detailed knowledge and experience working with the Registry should attempt to change the default TCP/IP

However, other TCP/IP settings may be established or Network icon in the Control Settings window. Next, click

formation. The appearance of these dialog boxes may vary depending on which operating system you are using.

TCP/IP Configuration ConceptThe Windows Registry database contains the TCP/IP configurations, in addition to othehardware and software configurations. Only administrators who ha

parameters in Registry Editor. changed by first clicking on thethe Protocols tab, right-click on TCP/IP Protocol, and click Properties. This opens the TCP/IP Properties window and you can now click on the appropriate tab and enter your configuration in

IP Address

Here, you may specify a particular IP address, or click the radio button next to “Obtain an ss automatically,” and the computer will capture one from the DHCP server.

information in the appropriate fields.

Default Gateway

.

IP addre

DNS

You can enable or disable DNS. Click the radio button to enable DNS, and enter the

Type the IP address of the gateway routers you have installed on your network. Use the “New” and “Add” command buttons to add a new gateway to the list of installed gateways. Whichever one appears first on the list is considered the default gateway. On some screens, you will need to type in the specified default gateway



WINS

Windows Internet Naming Service (WINS) is central to Microsoft’s networking topology. WINS maps NetBIOS names to IP addresses.

DHCP

Dynamic Host Configuration Protocol (DHCP) is used on a TCP/IP network to send configuration data to clients. This information includes the TCP/IP address configuration, default gateway, and subnet mask configuration. It also includes the DNS configuration.




Keyword Definition

ARP

BOOTP

Class A IP Address

Class B IP Address

Class C IP Address

Default Gateway

DHCP

DNS

FTP

HOSTS file

HTTP

HTTPS

ICMP

ICS

IMAP4

IP

IP Address

LMHOSTS file

NAT

NetBIOS

Octet



Keyword Definition

POP3

Port Number

Proxy Server

SMTP

SNMP

Subnet Mask

Subnetting

TCP

UDP

WINS



r protocols used within TCP/IP.

10. h e leading bit (one on the far left) for a Class A IP address? Class B? Class C?

process of breaking an IP address into _________ and ________

Review Questions Chapter 8 1. What are the four layers that make up the TCP/IP protocol suite?

2. How many primary protocols are used to make the TCP/IP Suite?

3. Name three of the five othe

4. What is the purpose of DNS?

5. What is an FQDN and give an example?


7. Who is responsible for maintaining top-level domains?

8. Which of the name resolution services will work only in Windows?

9. IPv4 addresses consist of a ______ bit number.

W at is the value of th

11. Subnetting is thegroups.

12. What are five reasons to use subnetting?



Chapter 9 – TCP/IP Utilities


Chapter 9 – TCP/IP Utilities One of the advantages of using TCP/IP as your network protocol is that it comes with several utilities that you can use to validate and troubleshoot the network. In addition, you can obtain several third party software packages that will help you manage a network.

Network Managers - SNMP Simple Network Management Protocol (SNMP) is an open protocol that allows third party software vendors to create products to manage networks. Using one of these products, you can remotely monitor any SNMP compatible device. The following are several SNMP managers:

Hewlett-Packard Open View

IBM NetView

InterMapper (Macintosh)

MRTG (Multi Router Traffic Grapher – UNIX)

NetMinder

Sun Net Manager

SNMP utilizes three elements for the complete system:

The management system software

The agent software

Communities

Management Software

This is the primary software package that is used by the administrator. It is run on a single computer and is used to access any SNMP devices and collect data. The data is then compiled in a database called a MIB (Management Information Base). From the database and the software interface, the administrator can create reports and charts that define the status of the network.



Agent Software

the SNMP compliant device. It will respond to commands

t-next: request the next value in a sequence.

DOS prompt.

The agent software resides onissued by the management software. The three commands are:

Get: request data from the device.

Ge

Set: sends a configuration value to a device.

An additional SNMP command is the trap. This command will capture any errors and problems that occur on the agent device and send it to the manager.

Communities

Communities are logical groups consisting of at least one manager and agent (usually several agents are assigned to one manager). The value of using communities is to limit the number of managers and agents. A community can also restrict access, therefore providing a level of security.

Validation Tools TCP/IP provides several command-level tools that can be used to validate various parameters within a network. These commands can be entered from a



hat will allow you to log any events and errors. This

Event Viewer Event Viewer is a Windows utility tincludes critical system errors, and TCP/IP events and errors. Note in the graphic below that an icon indicates that the event is critical (a stop occurred), serious (!), but did not cause a stop, and normal (i).

ROUTE The ROUTE command will show you the routing table and allow you to make edits to it.

olved by both broadcast and the WINS service. Nbtstat -R both purges and reloads the remote name cache table.

NETSTAT This command will display all the TCP/IP protocol statistics. Netstat -a shows all connections and listening ports. Netstat -e shows Ethernet statistics. Netstat -r shows the content of the routing table. Netstat -s shows statistics on a per-protocol basis.

TRACERT A Trace Route command-line utility, TRACERT, shows every router interface that a TCP/IP packet passes through on its way to its destination.

NBTSTAT This command will display NetBIOS over TCP/IP statistics. Nbtstat -c provides the remote name cache with the IP addresses. Nbtstat -n provides local NetBIOS names. Nbtstat -r provides names res



Hint: Use these line commands by click button in your taskbar, clicking Run, r cmd or command.

ing the Startand typing in eithe



TCP/IP also provides several useful troublmo apter.

IPCONFIG/WINIPCFG These commands are the same, and will display the current configuration of a computer. IPC N on the START menu.

IFCIFCthisreac

-

s)

The lowest level test to find out if you have connectivity to a remote host. Ping works at en higher-level TCP-based services cannot.

ping -n pings the IP address more than once.

UP -

system information for the domain. NSLOOKUP -s lists well-known services of clients in the domain.

TROUBLESHOOTING TOOLS eshooting tools. The following three are the

st common and are covered in more detail in the next ch

ONFIG is entered from a DOS prompt and WINIPCFG can be used from RU

ONFIG ONFIG displays the status of the network interface configuration. You should use command when you want to verify a user’s configuration or if there are problems hing a remote host.

ARP ARP will allow you to find the physical address (MAC address) of a computer by using the IP address of that computer. For example, the IP of a host might be 192.168.12.1, andyou would use this IP to find its MAC address or its physical address, which might be 0000-05-67-FF-33. Arp -a displays the current ARP entries (resolved IP to MAC addresseon your client. Arp -s is used to change the IP address of a device.

RARP RARP accomplishes the reverse of the ARP by using the known MAC address to find a host’s IP address.

PING

the IP level, and will often respond even whPing -t performs a continuous ping and

NSLOOKUP This command is used to troubleshoot DNS problems and can display the DNS entry for a given IP address. NSLOOKUP -t shows all records of the type specified. NSLOOKa shows aliases of clients in the domain. NSLOOKUP -d shows all records for the domain. NSLOOKUP -h shows CPU and operating






Keyword Definition

ARP

Event Viewer

IFCONFIG

IPCONFIG

Management Software

NBTSTAT

NETSTAT

NSLOOKUP

PING

RARP

SNMP

TRACERT



yze

Review Questions Chapter 9 1. You are the manager of a large network and have been getting complaints about the

system being slow. What kind of software package can you purchase to help analyour network?

2. In order for your new network management software to monitor the activities of the

entire network, each device will need to be _________ compliant.

3. TCP/IP provides several tools that you can use to validate statistics of your network. List as many as you can.

Chapter 10 – Network Security


etwork Security Chapter 10 – NSecurity is a vital aspect of a network that cannot be ignored. Password practices and procedures, data encryption, and firewalls are critical parts of your network. Select a

urity model that will meet the needs of your network and customize it as your

twork and to their own files (documents

g up E-mail addresses and initial passwords.

There are a number of reasons for maintaining a secure network. Once a company’s files

ing to it they want to do. Limiting access via passwords can prevent an inexperienced user, motivated by curiosity, from wandering into unprotected areas and

Although corrupting and deleting files accidentally can cause serious problems, you must

ss to your network for that matter, can deliberately damage your aos and costing thousands, or even millions, of dollars.

plan that will meet the needs of her particular network. A good plan will include the following considerations:

•

f sers should be held

basic secneeds change.

User and Share Level Users will have different levels of access, depending on the roles they play in your company. All users will have access to the nethey themselves have created). Most users will also be able to access shared files. Very few users will have access to administrative features, such as settin

have been set up for maximum access, unless safeguards are built in, anyone can get into any file and do anyth

inadvertently corrupting or deleting files.

also be prepared for the possibility of malicious intent. A disgruntled employee, or anyone who has accenetwork, creating ch

The best time to set up your network security, or at least have your plan intact, is right up front, before you set up the network. As you might have already deduced, the networkadministrator has complete responsibility for anything that happens to the network. Therefore, she must develop a

• Size of network

• Scope of network

Type and amount of usage of the network

• Who will have access to what

User-level Security

All employees should be assigned user names and passwords, as well as the levels opermission necessary for these individuals to do their jobs. Uaccountable for the security of their individual workstations. Most network security breaches are the work of someone from inside the company. Whether the sabotage is malicious, or an irresponsible prank, the results can be devastating.



hat cess, the user will be inclined to

be less attentive to personal security. Password protection is, among other things, a ere of confidentiality,

and cultivates a conscientious attitude toward security.

User-level security requires the user to logon using a Username and password. A erification method called “authentication” verifies the identity of a person or process. In manner similar to the signature on a document, authentication confirms that messages ceived truly originated from their stated source.

Privacy and confidentiality are important to most users. If the user is not able to trust tthe documents he or she creates are safe from outside ac

gesture of respect for the user and the system. It creates an atmosph

vare

User Logon

Share-level Security

With the share-level security model, passwords are assigned to network resources rather than to users. Users can access a shared resource, such as a template or another type of file. They can then copy the file to a local drive or a personal folder on the server. The user can edit the file as necessary, while the original file remains intact. Information on the shared drive cannot be changed by anyone other than the person who created the file. However, the file can be accessed by anyone who has the password and knows how to use it to access the shared resource.

The systems administrator should have an assistant or backup person who will have total access to the system, should the administrator be unavailable at a time when administrator access is required. A roadmap of all user names and passwords should be kept in a secure place, where the administrator can easily retrieve it.



Password Security



enhance the security of your network. Some will be more suitable to your system than others. Your security needs will

Firewalls

A firewall is designed to prevent access to your network from outside the company. It is plan. If you are accessing the Internet from your

network, you will most likely be using E-mail, at the very least. A firewall will need to be part of your security plan in order to prevent unauthorized access from outside of your network. Some firewalls will only allow E-mail to pass through, or they can be

Firewalls can trace calls and locate the computer trying to break in, but they are not e secrets or other types of proprietary ertain level, they can be host-based,

and work at the application level. Protocol-specific application proxy firewalls may provide increased access control, or auditing, by forwarding application traffic through

ified areas in the network’s security perimeter. As the system administrator, you will be responsible for choosing the type of firewall that best meets your network’s needs.

Security Techniques There are a number of techniques and practices that will

determine which techniques will best meet your system’s needs.

an important part of a network security

configured to suit your specific security needs.

particularly effective if your goal is to protect tradinformation. They can permit or deny traffic at a c

the firewall. Gateway hosts (also called bastion hosts) create fort

Firewall

Blocking Port Numbers

You can block port numbers for security purposes on your firewall or router so as to allow only specific traffic into your network. For example, if you wanted to block Internet traffic from entering your intranet, you would block port 80.

Backing up Data

Another integral part of network security is your backup system. Files need to be backed up daily, and even more often on larger networks. This needs to be handled in such a way that production will not be interrupted, and your company’s files and directories will be safe and available when you need them.



may make more sense to have two medium-sized servers, rather than one larger server, if one goes down the other can maintain network operations. Ideally, the second server ould serve as a backup to the first.

Most file server manufacturers recognize the need for data redundancy and thus, offer server equipment with multiple hard drives that mirror each other. If anything happens to one, the other can take over without compromising network operations. These multiple disks are called disk arrays, and are more commonly known as RAID.

Another more common form of backup is to a tape drive. Although slower than RAID, it is still a viable option.

Backup Options

Before we discuss the different RAID fault tolerance strategies, let’s discuss the various backup methods that are available.

As a computer professional, you know how important a backup plan is to the safety of your network’s data. Nothing will save you time and stress like an effective and thorough backup strategy in case the worst happens and your system crashes.

While planning your backup strategy, you must answer important questions about what to backup, where you will keep the backup information (on-site or off-site), and how often backups will be performed. In addition, your plan will need to include information about who will be in charge of performing the backups, how the backup information will be tested, and the procedure to follow for recovery.

Remember, those who fail to plan, plan to fail, so make sure not to neglect this important part of network security.

There are several options available, called the backup medium, for performing and storing data backups:

Removable Disks

There are two categories of removable disks: Small-Capacity and Large-Capacity. As you might guess, the small-capacity category includes the floppy disk. Floppy disk capacities today, range from 1.44 MB for the standard floppy disk to up to 250 MB capacities for ZIP disks. This backup medium is suitable for small companies.

Large-capacity disks include such options as the removable optical disk, which uses laser technology to read and write information onto a removable disk that has capacities of 128 MB to 650 MBs.

Tape Backup

This is probably the oldest and most popular backup medium in use today. The tape backup method is inexpensive and simple to implement. It also has large capacities of up to 50 GB for some systems.

Itsosh



Back It Up

Backup Software

Software programs or utilities are available that make backing up data easier and more efficient. Most operating systems come with a backup utility, but usually these won’t have the features available on a third-party backup program.

Full, Differential, and Incremental Backups

There are three backup types available: Full, Differential and Incremental. The Full backup, as its name implies, will backup all selected data on the network. This method will take the largest amount of storage media, but will be the easiest to restore.. This type of backup is usually performed weekly.

The Differential backup is used for backing up only the files that have changed since the last full backup. An archive bit is used to identify the files that have changed. When recovering from a failure, both the last differential backup tape copy and the last full backup tape copies will need to be used.

The Incremental backup is used for daily backups. This will reduce the amount of time needed to perform backups to the server, as only the data that has changed since the last backup will be copied. This method also uses an archive bit to identify which files have changed. To restore, the last full backup and all of the incremental backup tapes will be needed.

Volumes

Volumes are a way to organize storage disks so that the network operating system can store data on a disk. It is a named portion or chunk of disk space. A volume can be part of a disk or an entire disk.

Fault Tolerance and RAID

The ability of a system or component to continue normal operations, despite the presence of hardware or software failures, is called fault tolerance. This usually involves some degree of redundancy, and utilizes different means of dealing with security issues at this level.



s)

NOTE: The acronym for RAID has also been referred to as: “Redundant Array of

a

Disk Mirroring (RAID 1)

Disk mirroring or disk duplexing involves using one or more mirrors of a hard disk. The nt

a Ware,

opy of the data is spread across all of the disks based on a mathematical formula such that any one disk

that it

The following are common RAID (Redundant Array of Independent Diskspecifications:

RAID 0 - Non-redundant striped array (disk striping)

RAID 1 - Mirrored arrays (disk mirroring)

RAID 2 - Parallel array with ECC (disk striping with ECC)

RAID 3 - Parallel array with parity (disk striping with ECC stored as parity)

RAID 4 - Striped array with parity (disk striping with large blocks)

RAID 5 - Striped array with rotating parity (disk striping with parity)

Inexpensive Disks.”

Disk Striping (RAID 0)

The segmentation of logically sequential data, such as a single file, so that segments can be written to multiple disk drives (or other physical devices) in a round-robin fashion is called disk striping. If your processor is capable of reading or writing data faster thansingle disk can keep up, this relatively inexpensive technique can be very useful. However, if anything happens to one of the drives, the data in the stripe set is lost and cannot be retrieved. (Provides no fault tolerance.)

same data is written to two separate hard disks in order to preserve the data in the eveof a device failure. This technique may be applied in either software or hardware, and isstandard feature of RAID systems. Several operating systems, including Novell Netsupport either disk mirroring or disk duplexing.

Disk Striping With Parity (RAID 5)

The most common of RAID strategies, this one uses the parity method of ensuring that the data stored is really the same data that was sent. With this method, a c

in the set can be lost and the other disks will have a copy of all of the informationcontained. If more than one disk is lost, then the data in the entire array is also lost. Typically, administrators are alerted when one disk fails so that they can “regenerate” the RAID set before another disk has a chance to fail.

RAID 6 and Beyond

RAID-6 includes a second disk striping with parity scheme, which provides for even more fault tolerance. This, however, is not being used commercially at the moment to an



-ID-

-3

mmonly used and are not as likely to be on the test.

(generally by using SCSI). A SAN can either be centralized or decentralized. A ts together into one storage system. A RAID

N traditionally have been used for

Network-Attached Storage

ted ject to all the positives and negatives of that

hed to a LAN. It functions faster, since ter. It also has a bare-bones OS (microkernel) for

processing I/O requests.

otect your network from data loss due to power surges and failures. There are several tools on the market that will help prevent data loss from power fluctuations. In

more expensive ones. The equipment described able:

ent of s,

to

large degree. RAID 7 offers a real-time operating system and the functionality of a standalone computer. RAID-10 is comprised of an array of stripes (each stripe equals a RA1 array), which allows for better performance. Cost, as you might guess, is an issue. RAID-53. is like RAID-10, but uses a striping scheme where each stripe is a RAIDarray of disks. Like RAID-10, it offers better performance, but at a greater cost. These types of RAID are not as co

Storage Area Network (SAN)

A SAN (Storage Area Network) is a back-end network connecting storage devices

centralized SAN generally ties many hossystem is the most common example of a centralized SAN. A decentralized SAN connects multiple hosts with many storage systems. SAthe purposes of archiving data that is needed but infrequently used. SANs are channel attached whereas NASs are network attached.

Network-attached storage (NAS) is hard disk storage (RAID) like SAN, but it is treajust like any node on the network and is subidentity. It is assigned an IP address and it is attacit is not dependent on another compu

Fault Tolerance and Power

You need to pr

this case, the best tools seem to be the below is among the best avail

UPS (Uninterruptible Power Supply)

A UPS is battery powered, and guaranteed to provide power to a computer in the evinterruptions in the incoming electrical power. There are different types of UPS deviceand each type provides power for a different length of time.

An Interactive UPS (also called an “intelligent UPS”) connects to the computer's serial port and provides information, such as battery time remaining, allowing the computer shut down before complete loss of power.

Surge Protectors

Surge Protectors, also called surge suppressors, are power strips that provide protection from voltage spikes, surges, and sags in the power supply.



log on to the network.

ation such as budgets, personnel records and other r passwords at least every 30 days. Policies that spell

out pas ill know what is expected of them. This holds users accountable for their actions on the network, and discourages them fr

The mo at are the maximum number of characters and use a combination of letters, symbols, and numbers. Passwords should be changed more frequenchangedays. So, an effective password policy is one in which passwords change on a regular basis, include characters, numbers and symbols, but are easy enough that users can rememdown w

The imphysica No one, no matter who they are, should be given the opportunity to look through another person’s desk while they are not there.

to

their e

effective, management must randomly check to make sure that the policy is being

Evaluate your security policy on a regular basis to ensure that it is up to speed, and e the trouble starts. This is known as a security audit.

Password Practices and Procedures A network administrator may encrypt password information that is automatically sent to the server when users

Users working with sensitive informconfidential data should change thei

sword procedures should be given to all users so they w

om wandering into unauthorized areas.

st effective passwords are ones th

tly in high-security networks. Some “classified” networks require password s every day, but most networks can get by with changing their passwords every 30

ber them. Password security is compromised if a user writes his or her password here it might be seen by others.

portance of users logging off and locking their workstations when they are not lly using them cannot be stressed enough.

If the network administrator needs to use the workstation, he or she will know how accomplish the task. There is no reason for anyone other than the user to access the user’sfiles, so why make them available by not cleaning off your electronic desktop when youleave your workspace?

Many large companies implement a “clean desk policy.” What this means is that if the employees leave their workstations (for any reason) they are required to clean off desks or workstations and lock documents, etc. away. In order for this policy to b

applied.

troubleshoot befor



Encryption

mble passwords on an internal network so that they may not be

rk.

Internet

ndard) is the fastest and easiest method of sending an se the sender and receiver use the same key to decrypt the data.

tion

e The

and the recipient’s private key is used to decrypt it.

Data can be encoded at the sender’s end and decoded at the recipient’s end so that no one, other than the person for whom the message was intended, can understand the message. This practice is called cryptography and the system is called a cryptosystem. Encryption converts regular text into ciphertext by combining the original data with one or more “keys” known only to the sender and recipient. These keys are numbers or strings of characters combined with the original text to create an algorithm.

Encryption is used to scrastolen during logon. It is also used to secure data over VPNs (Virtual Private Networks). A VPN is a network that uses the Internet to connect remote users to an internal netwoEncryption is also used to encrypt E-mail transmissions, and is used extensively for online commerce (e-commerce) and online banking.

Without encryption the Internet would be a hotbed for high-tech thieves who could tap into it and steal information and credit card numbers. Even with encryption, theis not the most secure of environments.

DES (Data Encryption Staencrypted message, becauDES was developed by IBM and is now the most commonly used Private Key encrypsystem used. This method uses a 56-bit private key.

RSA is a public-key cryptosystem for both encryption and authentication. It was inventedin 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman. The name comes from their first initials. The entire security of RSA depends on the difficulty of factoring large primnumbers. RSA (Rivest-Shamir-Adleman) uses both a public key and a private key. recipient’s public key is used by the sender to encrypt the message,



ng a public key and the receiver decrypts it using a private key. If the receiver wishes to respond, the message is

original sender’s public key. The recipient of the response would te key to decrypt the message.

th parties have the same key, which is used to encrypt data and to decrypt it.

ncryption and was developed to not a completely secure encryption

Disaster Recovery

RP) lays out how an organization or business is to deal with

, on

Ensuring the integrity of your network infrastlocation and at backup sites, will ensure a mu quicker recovery.

Viruses

Viruses are those nasty little programs that can wreak havoc on a computer and its data. There are over 60,000 known viruses. The sole purpose of a virus is to replicate and make life miserable for computer users. Many viruses are simple annoyances, but some of them can cause irreparable harm to files. Most viruses are written by hackers who are trying to show off.

Viruses can be spread by various sources including: shareware, files downloaded from the Internet, software from unknown origins, and bulletin boards.

There are four basic types of viruses:

File Infectors: These attach themselves to executable files and spread to other files when the program is run.

Boot Sector: These replace the master boot record (or boot sector on a floppy). They will write themselves into memory any time the computer is booted.

Extra data appended to a message, which identifies and authenticates the sender and message data using public-key encryption, is called a digital signature.

Public Key encryption uses the Diffie-Hellman algorithm and is a one-way type of encryption method. The sender encrypts the message usi

encrypted using thethen use their priva

Symmetric Keys can also be used, but they are less secure. With this method of encryption bo

PGP (Pretty Good Privacy) is based on Public Key eencrypt E-mail messages. As the name implies, it ismethod.

EES (Escrowed Encryption Standard) is known as skipjack and uses an 80-bit key. It is similar to DES, but the use of the 80-bit key makes it much more complex. Skipjack was originally designed to be integrated onto a chip known as a clipper chip.

A disaster recovery plan (Ddisasters. It is designed to offset or minimize the effect of a potential disaster on the business or organization. It should keep the mission-critical functions first and foremostso as to allow the business or organization to quickly resume their activities. Preventishould also be addressed in the plan. Since the financial impact on a business can be severe if even down for an hour, much less a day, it is imperative that all possible disaster scenarios be addressed.

ructure to the best of your ability, both on ch



Trojan Horses: These appear to be legitimate programs, but when loaded, they will go to

ent, just from running a program. re very valuable, they mean that when you open a document

re are several measures you can take to prevent or at least minimize the damage:

virus program—there are several good ones on the market. Make sure it s that you use.

nts applications from writing to the boot section of the hard disk), enable it! This setting must be disabled before installing a new operating system.

Many viruses are transmitted by floppy disks. Be careful when reading floppies of unknown origin or using your disk on unfamiliar machines.

These days, many viruses and macroviruses are transmitted over the Internet. Use extreme caution when you download files, especially if they come from sources other than a manufacturer’s Web site. The most secure protection against Internet-distributed viruses is to make sure you have an antivirus program running at all times (or at least when you’re downloading and first running new files).

Trust no one when it comes to loading programs on your machine.

Keep your anti-virus program updated. Hundreds of viruses are written each month.

work on the system.

Macro Virus: These attach themselves as executable code to documents and run whenthe document is opened. (They can also attach to some kinds of E-mail). It used to be true that you couldn’t get a virus from opening a documUnfortunately while macros ayou are running a program.

Unfortunately viruses have become a way of life in the computer world. With this in mind, the

Purchase an antiis compatible with all of the operating system

If the computer has a BIOS setting that allows you to disable boot-sector writes, (preve





KEYWORDS Exercise . Hint: There’s a glossary in the back of this book. Define each of the following keywords

Keyword Definition

Data Encryption

Differential Backup

Disaster Recovery

Disk Mirroring

Disk Striping

Firewall

Full Backup

Incremental Backup

NAS

Password Security

RAID

SAN

Share Level Security

User Level Security

Volumes



Review Questions Chapter 10 . What are the two requirements of user level logon?

2. In a share level model, passwords are assigned to __________.

does encryption play in your security model?

1

3. What is the function of a firewall?

4. The acronym RAID stands for __________.

5. What are the three common levels of RAID?

6. What purpose



Conclusion


twork Chapter 11 – Troubleshooting a NeBeing a computer and network professional automatically implies that you are a troubleshooter. If fact, troubleshooting comprises perhaps the single largest aspect of working with computer and network hardware and software. After all, if you are the expert, you will most likely be called when there is a problem, not when all is well. The majority of this course has fo networks. This chapter will focus on the application of th g an effective troubleshooter does not come automati ing knowledge (even though it is implied). Troubleshooting is an art and can hat you must learn is how to appro nsome es, ou can em

Basic Troubleshooting As mentioned, troubleshooting is moretechnicians troubleshooting comes naturally, while for others it is a struggle. For those who must endure the struggle, a habit of applying a methodical and determined approach will s econd n rt approach that will lead to successful tro : establish the symptoms, identify the aff , select the most probable cause, implement a solu l effects of the solution and document the soluti ke your next troubleshooting exercise easi

Establish t ptoms:

Defining a problem is not always as sim well defined by the person who calls and co equently the problem, “as reported,” is really just the symptom and not the true cause. To make matte at middle of a job, or when there is a deadline and ded frustr ds to confusion and he cause, not the symptom. As a troubleshooter, y eliminate as many alternatives as possi can focus on the things that might be the cause of the problem. In order to do this, you must be organized.

The first step is the most critical and ofunderstanding of the problem (the entir eal of time working on the symptoms instead of th are a pad of paper, a pen (or pencil), and go

Be sure to listen carefully to your clien computer or network is your best source of information. Don’t assume that just because you are the expert, the operator doesn’t know what caused the problem. They may not know the technical reason for the failure, but they often hold the keys to the problem. Remember,

cused on the facts and science ofese facts to solve problems. Bein

cally with networkbe learned. W

ach a problem in an organized a basic troubleshooting techniqu

ploy to simplify the process.

d methodical manner. This chapter will begin with and progress with some specific tools that y

of an art form than a science. For some

oon result in it becoming s ature for you. Let’s take a look at an eight-paubleshooting. The eight parts are as followsected area, establish what has changedtion, test the result, recognize the potentiaon. It is proper use of all the parts that will maer.

he sym

ple as it sounds. In most cases, it seemsmplains! But is it really defined? Fr

rs worse, computers never fail

ation often lea

a convenient time. They always fail in the the user must have it fixed now. This ad

stress. Remember, you are looking for tyou must be able to quickly and confidentlble, so that you

ten the most ignored. Without a complete e problem) you can spend a great de cause. The only tools required for this phaseod listening skills.

t or co-worker. The user of the



ou may know how the computer and network runs and can find the technical cause of e failure, but the operator was there before (and after) the problem started and may

recall ecific questions to jog their m probl t occurred. Do not make th rtantly, do not intimidate the user.

Ask a few questions to help identify the occurred before the failure. You may want to cre th these questions (and others specif or taking note

When did you first notice the problem?

What has changed since the computer w (New Software, network or computer m

Show me how to create the error.

Describe any changes in the computer (noise, screen changes, lights, and so forth).

Are you the only one having the proble

Did anyone else use this computer?

he list of questions could go on forever. You will need to create your own list based on the situation. With a little experience, you will be able to identify the best questions for the situation.

Identify the affected area

The next step involves the process of isolating the problem. Isolating the problem is the art of eliminating what you know from what you don’t know. For example, if a keyboard is not working and you connect a known good keyboard to the computer and it works, you have isolated the problem to the keyboard or its cabling. There is no particular approach to follow and there is no substitute for experience. The best you can do is to eliminate any obvious problem and work toward the more complex. The purpose is to narrow the search down to one or two general categories. Be sure to observe the failure yourself. If possible, have someone demonstrate the failure to you. If it is an operator-induced problem, it is important to observe how it is created, as well as the results.

Establish what has changed

The most difficult problems to isolate are the intermittent ones. These never seem to occur when you are present. The only way to resolve these is to be able to re-create the set of circumstances that caused the failure. Sometimes, the process of elimination is all that you can do. This will take time and patience. The user will need to keep detailed records of what is being done before, and when, the failure occurs. One thing that might

yth

the events that led up to the failuemory, or help

em firs

re. You may, however, have to ask some spthem focus on what was going on when thee questions too technical, and most impo

problem and list the events as theyate a form wi

ic to the situation) f s:

as last used?

oved, recent software upgrade.)

m?

T

Conclusion


help in such cases is to tell the user to not do anything with the computer when the y the “evidence” is not disturbed.

this

The first step of any plan should be document and back up. Do not make any ave

Once a plan is created, it is important to follow it through. Jumping around and randomly trying things can often lead to more serious problems. Document every action and its results. If the first plan is not successful (it won’t always be), create a new plan based on what you discovered with the previous plan. Be sure to refer to any assumptions you may have made.

In the case of a network problem, the first step in isolation is to separate a network (hardware) problem from a workstation problem. For example, is the problem occurring on more than one workstation or is it only on one? If you determine that the problem is only on one workstation and the cabling and network card are working properly, then you need to further isolate the problem to determine which program is experiencing difficulty. If for example, you can “see” other computers in the network neighborhood, but you cannot receive any E-mail, then you know for sure that the network is physically working, but something must be wrong in the E-mail software or configuration.

The general procedure for iso art globally and work to

A workgroup or domain

A server or workstation

A workstation or user

problem recurs, but to call you. That wa

Isolation of a problem requires a structured approach. It requires two simple steps, makea plan and follow it.

Select the most probable cause

Make a Plan and Follow it from Beginning to End

Create a planned approach to isolate the problem based on your knowledge at point. Start with the most obvious or easiest solution to eliminate, and move forward. Write down your plan!

assumptions. If you must make any assumptions, write them down. You may hto refer back to them later.

lating network problems is to stlocally. Starting from the top, isolate the problem to:

A WAN or LAN

A segment of a LAN



Once the search has been narrowed, start looking for specific hardware:

Routers

Hubs/Concentrator

Cabling or Connections

Adapters

Software related problems could also be isolated to several causes:

Protocols

Authentications

d confused operators can lead to further problems. Here are a few suggestions for isolating the hardware/software from the operator:

Have another operator perform the wn workstation, as well as the one that is causing problems. It is important

how.

Implement a solution

After locating or at least narrowing the problem to a few possibilities, either repair or replace the defect. With hardware, repair or replacement is usually all that is needed. However, if the problem is software or configuration related, it may require some additional effort. To resolve these types of problems, you must do three things:

Formulate a correction (write down what you think will resolve the problem).

Test the correction (make sure that the changes work).

Implement the solution.

Note: If the problem is software the “before” and “after”

As often as not, the problem may be caused by the operator, and not the hardware or the system. In these cases, you must be careful as to how you resolve the problem while not alienating the operator. Frustrated an

same task on their oto use another operator. This will keep you

removed from the problem and eliminate the “it always works for the expert” syndrome.

Confirm that the operator is using standard operating procedures. This means to have the operator duplicate the problem while you watch – do not tell them

-oriented, be sure to recordchanges.

Resolving operator-induced failures is more difficult than hardware induced failures. In these situations, you must be very careful to treat the cause and not the symptoms. For example, if an operator is afraid of computers in general, no amount of training or instruction will solve a problem until that general fear is removed.

Conclusion


separate the true professional from the amateur. Many troubleshooting

ation that the job is done. Confirmation means to solution and confirm

satisfaction.

did not create other problems. You have not done a professional

ted.

he problem and the repair. This means to document (in writing) the lem, and the repair. In troubleshooting, there is no substitute for

in m (or one like it) happens again. This is one way

to build, maintain, and share experience.

Now we want to and repair services operate on the fix and run principle. The basis for this policy is that once the system is running, you are wasting your time and should be working on the nextproblem. The reality is that the time you spend after the repair can save repeat service calls and shorten the time-cycle for future service calls.

Test the Result

No repair is complete without confirmmake sure that the problem no longer exists. Ask the user to test the

Recognize the potential effects of the solution

Make sure that the fixjob if the repair was completed at the expense of something else. Confirmation of the repair can save you a return trip to repeat the fix or to correct a problem that you creaConfirming the repair may include some form of feedback from the user, or a follow upcall just to make sure all is well.

Document the solution

Finally, document tsymptoms, the probexperience. You must look at every new problem as an opportunity to expand that experience. Keeping a copy of the repair procedure in your technical library may come handy in a year or two when the proble



n, a network troubleshooter will need a few tools to m sier. Networking tools can be divided into two cat ware tools.

Hardwa

Before he integritcabling

Wire C

The wi ts copper wire as well as crimping solderlewire.

Networking and Troubleshooting Tools Just like a good computer repair technicia

ake the process of troubleshooting eaegories: hardware tools and soft

re Networking Tools

we get into the tools that are designed specifically to troubleshoot and ensure ty of your network, let us quickly cover some tools used to setup the network .

rimper

re crimper is a versatile tool that strips and cuss terminals. The narrow nose with its serrated jaws is used for pulling or coiling

Wire Crimper

Down Tool

own tools are used to “punch down” cabling to “blocks” in your wiring rack.

Punch

Punch dThey secure the connection between the wires and the block.

Punch Down Tool

Conclusion


shorted. An open conductor

The name multimeter was derived from its ability to measure several different parameters. You can test for AC and DC volta e meters will let you test for current a than 10 amps). With it you can test various electronic com power in the computer. Most will consist of a digital or analog meter or display, a pair of wires with probes (one black and one red), and a switch for adjusting the range of settings to be measured. The red wire is the positive probe and the black wire is the negative or ground probe. When working with network cabling, we will have to know how to test for continuity.

The purpose of continuity testing is to confirm a complete electrical circuit. For example, it is to check to see that a wire is not broken. Most multimeters have a “continuity” setting, which will indicate a complete circuit by either a light or a sound. When you connect both leads of the meter to each end of the device you are testing, a positive test (the light comes on or it makes a noise) means that the circuit is complete. If the test is negative (no light or noise), the circuit is broken. If your meter does not have a continuity setting, it is still possible to test for continuity. All you need to do is use the resistance setting and test the device. In a wire for example, the resistance reading for continuity would be zero – meaning that current is flowing without resistance. If the wire is broken, the resistance reading will be infinity or maximum – meaning that no current is flowing.

Media Tester

Media testers are usually devices used to test the cabling, whether it be RJ-11 or RJ-45. They can check for continuity and how the pin outs line up. These devices are generally used when you make your own cabling.

Hardware Troubleshooting Tools

Hardware troubleshooting tools are used to confirm the integrity of the cabling. Network cabling is, in principle, very easy to troubleshoot. Since it is made up of wires, you can have only one of two problems. A good cable will provide continuity or current flow from one end to the other. A bad cable will be either open ormeans that the cable is broken and the current will not flow from one end to the other. Ashorted conductor means that the current is flowing to ground or another cable instead ofbeing isolated. These failures are like a water pipe that is broken (open) or has a leak (shorted). There are several tools we can use to check for open and shorted wires. We will start by looking at a multimeter, which is one of the most basic tools for electronic troubleshooting.

The Multimeter

ge, resistance, and continuity. Soms well, but only low amounts (less

ponents, as well as the electrical



Network Tester

Tone ne Locato

A mu r is a universal tool and almost any electrical or electronic technician should have one. The problem when using this tool for testing continuity of a network cable is the length of the cable. If both ends are in the same location, this is not a problem. However, if the cable is a hundred feet long and spans the length of a building, testing for conti an additional wire. You can use a pair of wires (very common in network cables) and connect the two wires at one end, and test at the other end. However, there than not, several airs of wires at one end (the hub or patch panel). The question then becomes which pair goes to which room? Solving these problems with continuity testing can take a long time unless you are just lucky.

Telephone and phone wiring companies use two tools, called tone generators and tone locators, to find pairs of wires in a bundle. The tone generator is connected to the wires at

e known location (the room with the outlet). This applies a signal on the wires. The tone locator is a receiver that is set to the frequency of the generator. When the receiver is placed in close proximity to the wire that has the signal applied, it will emit a tone, thus locating the wires. When used together, these tools are often called a fox and a hound.

Generator and To r

ltimete

nuity will require

are more often p

th

Conclusion


ne Generator

Test Cables

a neloopback and the crossover cable. A loopback cable is just what the name implies. It is a single-ended cable that connects to a network card. It has the transmit and receive wires connected. Any signal placed on the transmit wire will loopback to the receive wire, and

r ou are able to send a signal and have it return, you will know that the network card and the protocol stack are functioning. A crossover cable is similar to a loopback, but is double-ended. The transmit wire on one connector is connected to the receive wire on the other (and vice versa). These cables can be used to

e care they look just like patch cables but are not interchangeable.

Ti

anced tools that may tometer (TDR) is used

to find breaks and shorts in network cabling. By calculating the time it takes a signal to travel the length of a cable and to be reflected back, the location of any break or short can

Protocol Analyzer

onitor and analyze network traffic. Software analyzers, fers, are usually a PC with a special network card. They will

generate reports. Many protocol analyzers ill include a TDR as one of their functions.

To

One method of isolating problems is to use a special cable to remove a workstation from twork and simulate that it is still connected. Two such cables are the hardware

the efore back to the network card. If y

connect two computers into a single network eliminating any other network hardware. Bful when using a crossover cable, because

me Domain Reflectometer

For those who are serious network troubleshooters, there are advwell be worth the time and investment. The Time-Domain Reflec

be determined.

A protocol analyzer is used to malso called packet snifmonitor network traffic, capture packets and w



s

Optical Tester

Optical Testers or optical time domain reflectometers (OTDR) are essentially the same as a TDR, but used for fiber optic cabling. OTDRs also calculate the locations of breakby the amount of time it takes for a signal to travel the length of the cable and back.

Conclusion


aintaining and Troubleshooting Networks aintaining and troubleshooting networks differs from operating system to operating

system. Therefore, you will need to refer to the operating systems’ manuals for detailed troubleshooting procedures. The following table provides some generic troubleshooting concepts:

Network Troubleshooting

MM

Situation Probable Cause

A single workstation does not connect to the network.

Usually these are authentication errors, but can be caused by a disconnected cable.

Authentication A common failure is for a user to be unable to logon. Often these are caused by typos when entering user names and passwords. Some passwords are case-sensitive, and a stuck caps-lock key can cause errors.

Common Mode Failures Common mode failures are generated when one component of a LAN causes the entire LAN to fail. An example would be a network card that begins to continually broadcast useless information and overloads the network. This is sometimes called a broadcast storm.

Loss of Data If data transfers are incomplete or inaccurate, check to ensure all network cabling and connectors are intact.

Network Security Violations (Insufficient Rights or Permissions)

Anything that breaks the integrity of the data on a network is a break of security. You can’t access a resource unless the administrator of the network has allowed you to do so.

Reduced Bandwidth Reduced bandwidth is just like a traffic jam. For some reason, the traffic is not moving, due to either excessive traffic or a bottleneck. A bottleneck is any resource that limits the rate at which network traffic can be moved. It could be the processor, the network, or a disk resource.



Slow Loading of Programs and Files

Fragmentation occurs when the operating system saves, deletes, and moves information. You must defragment the drive. If slow loading persists even after defragmenting, check for memory bottlenecks.

Traffic Overloads As networks grow, so does the traffic. When the amount of traffic exceeds the ability of the network to carry it, the network slows down. These problems can be addressed by segmenting the network and scheduling non-critical work for after hours. For example, tasks like backing up drives or moving large amounts of data can be done at night.

Unauthorized Software You must manage software distribution to ensure users are not loading non-licensed software and computer viruses onto the network drives.

Conclusion


rotocols

are unable to see any other workstations or e and

nd TRACERT commands to test the network. prompt. TRACERT allows you to trace the

o hat a packet takes to its destination. It also lets you know the tim es in handy if you need to see where exactly on your

r going.

opback address. This will test the protocol stack in the ss is 127.0.0.1. Remember this address, because as a

Troubleshooting Scenarios The following summarizes some possible scenarios that you may encounter and how to provide a solution:

Misbehaving P

You have just installed a new workstation and servers on the network. If you are using TCP/IP, you can confirm your hardwarprotocols by using the IPCONFIG, PING, aThese commands work from a command“h ps’ (routers encountered) t

e that it takes. This comint anet or on the Internet your packet is

The first step is to PING the locomputer. The loopback addrenetwork professional, you will use it often.

PING th ck Addres

The next step is to NFIG to ge about your rkstation. On a Windows 95/98 computer, you can use the WINIPCFG command from the RUN dialog box in the START menu. This command will give the s me results as IPCONFIG from DOS, but looks better and includes the MAC address of the network adapter card. On a Macintosh system, open the TCP/IP Control Panel to use these utilities.

e Loopba s

use IPCO t details wo

a



Notice that the IP addr

If you are using Wind k like the following. This command is only x and ME and will not work on a Windows NT,

P, or 2003 sys

ess of this computer is 195.55.48.6.

ows, WINIPCFG, your dialog box will loo for Windows 9

2000, X tem.

WINIP G

You can now PING that address to determine if the network card and protocol stack for the computer are working properly.

CF

Conclusion


5.48.

Continue the process by PINGing another workstation, the server, and so on. With each ep, you will be testing a larger portion of the network. If at any stage, you receive a essage like the following, you have encountered a problem.

PING 195.5 6

stm

Problem PING Found a

yo reach a host computer, then there is a problem with the protocol. ddress, or the computer you are PINGing is

t u mply m not logged on to the netw

r t e ipxping com

Cable Problems

rk or they don’t. The biggest problem with em that since they wor

connections and loose connectors cause most cable problems. Here are some suggestions hen

IfUsually this m

u are unable toeans you have the wrong IP a

no sing the TCP/IP protocol. It could siork.

ean that it is

Fo he IPX/SPX networks, use th mand.

Cabling problems are simple: either they woth is that we often assume ked yesterday, they must be okay. Poor

w you suspect cable problems:



Any time a computer was moved and it suddenly stops responding to the network, cable.

on the adapter card. If present, they will let you know if the card is working and if it can access the network.

IC Indicator Lights

Many network cards have from one to three r yellow) next to the cable connector. These lights can be seen from the back of the computer. The actual function of each light will depen turer and you may have to check the documentation that came with the c er or not the card can detect the pre is being transmitted. If no lights are can be sure t being detected, while green lights indicate that all is well.

Name Resolu

You are testin workstati see the workstation by its domain name. You know that the IP con ause you can PING the IP address. How do you ne the prob

One network problem encounter lier, we learned that workstations, s, have two ess number, (which the computers like) and the other is we humans like). Somewhere in the system is a table or data number to na vise versa. ain Name Server). To resolve this problem, you will need to use slookup.” With nslookup, you can connect direc access the information stored there.

Another place to look for name on a local LAN) is in the HOSTS and LMHOSTS files. These are text files that are used to statically map local and remote hostnames and NetBIOS names ectively. If these files are being used, you can find them on the host in the systemroot\system32\driver directory. The difference etween HOSTS and LMHOSTS is that HOSTS is used in place of DNS and LMHOSTS

is used in place of WINS.

Performance

You think that your network is performing without problems, but are starting to get complaints that “the network is slow.” What are you going to do?

These problems are often difficult to resolve because there are a vast number of possibilities as to the cause. If there is a sudden change in performance, the first thing to do is find out what has changed. Any new hardware or applications (including upgrades) are always good candidates for the problem. Beyond that, we need to look at four limiting factors on performance.

suspect a loose or disconnected

Replace any suspect drop or patch cables with a known good one.

Check the indicator lights

N

LED lights (green o

d on the manufacard for details. In general, they will indicate wheth

sence of a network and when dataon, you that the network is no

tion

g a new on and are unable tonection is good bec

determi lem?

ed is name resolution. Ear names. One is the IP addr or hostthe IP address name (which

base that provides the translations fromme and That location is the DNS (Dom

a TCP/IP utility called “ntly to the DNS and

resolution problems (

to IP addresses, resp

b

Conclusion


Bandwidth and Throughput

oughput are not the same thing, but are interrelated. You can

t and is measured in Mbps (Megabits per second). The bandwidth is the number of packets that can move past a point at any given time (also measured in Mbps). Think of the bandwidth as the number of lanes on the highway (the more lanes, the more packets that can be moved). Just like our highway, if the traffic gets too congested, everything slows down.

The perfo anc ly be as fast as th e entire system. Therefore, if any one component is performing poorly, it will affect the entire network.

Latency

Small de s in are caused by s called latency. Routers and switches that connect any two s cause these delays. Latency delays, for the most part, are negligible, but can be measured and will affect performance in large networks.

Application Efficiency

Any application th not designed to work over a ne will be unable to take full advantage of network protocols. This can slow down data transfer. For example, some network operating systems will allow for burst mode operation. This means that for a small amount of time, it can send data at a faster than rated speed. An application will have to be designed to take advantage of burst mode in order to use it.

Server/Workstation Limits

Nothing will slow down a network more than a sluggish server. A server that is operating its CPU at 100% will have to delay processing of each request until it complet s cu his may require the requestor to continue to resend its request, adding to the network load. A server with a memory deficiency will have to w in k cache. Reading and writing from a disk is much slower than from memory.

Resolving performance problems can be easy, after you identify the problem. The trick is knowing how the network performed when it was good and how it performs now. The answer lies in creating a performance baseline. A baseline is simply a record of performance criteria at a given time. To create a baseline, you will need to run a series of tests and record the performance. For example, if you are experiencing slow printing, you can print the same document at different times throughout the day and record the time it takes to print. From this information, you will know the high, slow, and average time to print the document. Then, at a later date, you can re-test the printer performance under the same conditions and determine if things have changed.

Bandwidth and thrthink of a network as a super highway and the vehicles as being packets of information. The speed limit, or maximum speed that traffic can move, is the throughpu

rm e of a network will on e slowest link in th

lay packet movement that devices iegments of a network can

at was twork

es it rrent request. T

rite formation to a dis



alled performance monitor for the server or network statistics software for th s has a built in performance monitor as part of its administrative tools. W monitor and collect data for a variety of events. With th ill be able to monitor such events as processor time, available memory, etc. Similar software packages (usually as part of a network analyzer) will collect data for packets/sec, percent of network utilization, etc.

The key to monitoring network performance is statistics. Network statistics will come from two sources – the server and the network. To collect these statistics, you will need to use some software c

e network itself. Windowith this activated, you can

is tool, you w

s Performance Monitor Window

Conclusion



Keyword Definition

Bandwidth

IPCONFIG

Latency

Media Tester

Multimeter

Performance Monitor

PING

Punch Down Tool

TDR

Throughput

Tone Generator

Tone Locator

WINIPCFG

Wire Crimper



1 1 are e primary steps to take when troubleshooting?

2. A r rep lem, are y with the troubleshooting pro ss?

3. You are troubleshooting a cable roblem. You have found the cabinet with the patch p l an t need to know which of the 50 cables goes to the accounting office. What would be the best tool to help you locate the cable in question?

4. You have located the cable in question #3, and think it might be shorted l w ld yo nd the shor

th a TCP/IP network and want to confirm the protocol stack in a . What utility can you use to confirm that the protocol stack is

. What is the loopback IP address?

7. You need to know the IP address of a work hat TCP/IP utility can you use to d th kst

8. You have just connected a workstation to the network. What is the easiest way to tell if net ne

. What is the difference between bandwidth and throughput?

10. You have a Windows 2000 network and received complaints that the server is running slowly. What utility can you use to determine the performance of the server?

Conclusion

Review Questions Chapter 1. What

the thre

fte airing a prob ou finished ce

p ane d hub, bu

. What tooou u need to fi t?

5. You are working wispecific workstationgood?

6

station. Wation? fin e IP address of the wor

the work card can “see” the twork?

9

Conclusion


This concludes our Network+ Training & Test Preparation guide. We hope that you have ork+ training journey as much as we have enjoyed providing it to you.

as often, as you like. To measure your retention of these materials, start taking s that are on the CD-ROM that was included with this course. After

king a practice exam, be sure to review any areas that need improvement. When you are consistently achieving scores in the 90% range, y ready to sit for your certification exam.

The following “Appendix A” is an excellent source of review material, and don’t forget to use the Glossary. When you are ready to schedule your exam, be sure to refer back to the beginning of this book for tips expe t the exam site.

We love to hear from our students, so if you have any questions, or if you just want to let us know how you are doing, we’d be happy to hear from you!

Remember, at Specialized Solutions, our success ectly tied to the success that our students have with our training and certification products.

hank you for allowing us to be your training partner and please let us know if we can help with any of your future training needs.

enjoyed your Netw

Remember, the best thing about a self-study course is that you are able to review it as much, andthe practice examta

ou are

on what to ct a

is dir

T



Appendix A – Tech Summary


Appendix A – Tech Summary The following tables summarize key information found in this course:

-4-3 Rule When installing coaxial Ethernet cabling, you must conform to the 5-4-3 rule.

• Maximum of 5 segments in a series.

• Maximum of 4 repeaters.

• Only 3 segments can contain nodes.

Coaxial Cable Types Not all coaxial cables are the same. They are specified based on their impedance. Impedance is a unit of measurement for resistance to AC voltages. It is expressed in ohms. In order for the network to operate at peak performance, all electronic components must operate at the same impedance. Using the wrong cable will cause poor performance and/or failure of the network.

5

Uses Type Impedance – Ohms

10Base5 Thicknet RG-8 50

10Base5 Thicknet RG-11 50

10Base2 Thinnet RG-58 50

Cable TV RG-59 75

ARCnet RG-62 93



Cable Description

RG-58 /U lid copper core. So

RG-58 A/U Stranded wire core.

RG-58 C/U Military spe tion of RG-58 Acifica /U.

RG-59 Broadband transmission, such as cable television.

RG-6 Larger in diameter and rated for higher frequencies

transmissions. than RG-59, but also used for broadband

RG-62 ArcNet netw orks.

Ethernet Cabling

Cable Type

Topology Max. Length

(meters)

Speed Mbps

Nodes Per

Segment

Max Segments

Max. Repeaters

Max Segments

with Nodes

10Ba axial Thicknet

4 3 se5 Co Bus 500 10 100 5

10Base2 Coaxial Thinnet

4 3 Bus 185 10 30 5



UTP Cable Categories

Category Wire Specs Uses

1 & 2 Suitable only below 4 Mbps. Voice ONLY

3 Fotwists pe

ps ur twisted pairs with three 10 Mbr inch.

4 Fotw

bps. ur twisted pairs with 4 ists per inch.

Data grade up to 16 M

5 Four twisted pairs with 5 twists per inch.

Data grade up to 100 Mbps.

IBM Cable Types (Token Ring) IBM has created its own standards for their Token Ring Networks.

Type Wire Specs Uses

1 Two STP solid core 22 AWG wires – maximum length 101 meters (331 feet).

Connect between terminals and distribution boxes or between different wiring closets.

2 Six twisted pairs, two STP and four UTP – maximum length 100 meters (328 feet).

Same as type 1, but adds voice capability along with data.

3 Four UTP with two twists per inch – 22 or 24 AWG wire –maximum cable length is 45 meters (148 feet).

Lower cost alternative to type 1 or 2. Cannot be used for 16 Mbps Token Ring. Voice-grade cable.

4 Not Defined

5 Two 62.5/125-micron multi-mode fibers.

Fiber Optic

6 Two STP – 26 AWG wire. Data patch cables.

7 Not Defined

8 Two STP – 26 AWG. Contains a shield for use under carpets.

9 Two STP –26 AWG wire. Plenum grade.



IEEE 802.x Standards The IEEE 802 standards work in the Physical and Data Link layers of the OSI Model. They also divide the Data Link Layer into two sub-layers: Logical Link Control and Media Access Controls.

802.x Standard Basis of Standard

802.1 Internetworking

802.2 Logical Link Control Sub Layer

802.3 CSMA/CD Ethernet

802.4 Token Bus LAN

802.5 Token Ring LAN

802.6 Metropolitan Area Networks (MAN)

802.7 Broadband Technologies

802.8 Fiber Optic Technologies

802.9 Hybrid Voice/Data Networks

802.10 Network Security

802.11 Wireless Networks

802.12 High Speed LANs



IRQ assignments can vary from computer to computer; however, there are some that are e and some that can be changed. The following is a standard configuration

IRQ Assignments

always the samfor IRQ settings:

IRQ Function Available for Change

0 System Timer No

1 Keyboard Controller No

2/9 Available Yes

3 COM2, COM4 Usually

4 COM1, COM3 Usually

5 LPT2 Usually-Often used for NICs.

6 Floppy Controller No

7 LPT1 Usually

8 Real-time Clock No

10 Available Yes

11 SCSI/available Yes

12 Available Yes

13 Math Coprocessor If no math coprocessor

14 Primary IDE No

15 Secondary IDE Usually



In addition to IRQs you may have to set the Base I/O address. The following are common address assignments:

200 to 20F – Game Port

210 to 21F

220 to22F

230 to 23F – Bus Mouse

240 to 24F

260 to 26F

270 to 27F - LPT3

280 to 28F

290 to 29F

2A0 to 2AF

2B0 to 2BF

2C0 to 2CF

2D0 to 2DF

2E0 to 2EF – COM2

300 to 30F – Network Adapter Card

310 to 31F – Network Adapter Card

320 to 32F – Hard Disk Controller (For PS/2 Model 30)

330 to 33F

340 to 34F

350 to 35F

360 to 36F

370 to 37F - LPT2

380 to 38F

390 to 39F



3A0 to 3AF

Modes)

3E0 to 3EF

3F0 to 3FF – Floppy Disk Controller

3B0 to 3BF – LPT1

3C0 to 3CF – EGA/VGA

3D0 to 3DF – CGA/MCGA (also EGA/VGA in color video

OSI Model



SI Model and Connectivity Devices: O

Layer Number

Name Devices

7 Application Computers

6 Presentation

5 Session

4 Transport

Gateways

3 Network Routers

2 Data Link Bridges Brouter

1 Physical NICs, Hubs, Repeaters Switches

Subnet Masking . Subnet masks are used to divide an IP address into its network address and host address

Subnet masks are assigned according to the following three classes:

Class IP Address Default Subnet Mask

Number of Networks

Number of Host

A 001.x.x.x to 126.x.x.x 255.0.0.0 126 16,777,214

B 128.x.x.x to 191. x.x.x 255.255.0.0 16,384 65,534

C 192.x.x.x to 223. x.x.x 255.255.255.0 2,097,152 254



ed on a network device. Common ports are as llows:

TCP/IP Ports A port is a virtual outlet that can be openfo

Service Port

FTP 21

TELNET 23

SMTP 25

HTTP 80

POP3 110

TCP/IP Utilities TCP/IP provides many tools for troubleshooting networks. Here are some command-line

configuration.

IPCONFIG Displays the basic local host configuration – IP address, the subnet address, the subnet mask, and default gateway.

PING Sends a test packet to a specified address. If all is well, it will return. Use the loopback address (127.0.0.1) to test the IP architecture and configuration.

ARP Used to see the entries in the Address Resolution table (uses IP addresses to find MAC addresses).

RARP Uses a MAC address to find an IP address.

utilities:

IFCONFIG Shows the Linux user’s network interface



ROUTE Used to see the local routing table and to add entries to it. Use ROUTE PRINT to display contents, ROUTE ADD to add entries and ROUTE DELETE to remove entries.

NBSTAT Used to check the resolution of NetBIOS names to TCP/IP addresses.

NETSTAT Used to check the status of current IP connections.

TRACERT Used to verify the route to a remote host. (Pronounced Trace Route.)

NSLOOKUP Used to verify entries on a DNS server.

Topology Review

In a bus topology, all computers are connected in a series.

In a star topology, all computers are connected to a hub.



In a ring topology, a circle.

ll computers are logically connected in a

In a mesh topology, all computers are connected to each other.



ransmission Media TMedia Bandwidth

(Mbps) Nodes/Segment Maximum Nodes

per Network Maximum Cable Length (meters)

UTP 4-100 1 1024 100

STP 16-155 Varies 260 100

CTh

10 oaxial icknet

100 300 500

CTh

90 185 oaxial innet

10 30

FiO

2000 1024 2000 ber ptic

1

Infrared 1-10 32 NA Varies

Troubleshooting Tools

Hardware Uses

o test voltages, resistance, and continuity of nic devices and circuitry.

Volt/Ohm Meter Used telectro

Cable Tester TDR – checks and locates breaks in cables.

Oscilloscope An electronic device that graphically displays frequency and malso beUsed with TDR to locate cable breaks.

Pr lso c to capture packet

agnitude of analog signals. Can used for precise voltage measurements.

otocol Analyzer A alled a network analyzer. Used s on a network and analyze them.



Software Uses

PeMonitor

Use to lay various performance parameters found on workstations, serversfor net

Ev Displa

SNMP Simple monitor network devices (servers, hubs, interface cards, routers, and bridges).

rformance monitor and graphically disp

, and networks. Used to provide information work baselines.

ent Viewer ys or prints a list of events.

Network Management Protocol – used to



Appendix B – Useful Web Sites


Appendix B – Useful Web Sites

Microsoft: http://www.microsoft.com

Novell http://www.novell.com

Other Helpful Sites http://www.cnet.com



Appendix C – Network Standards Organizations


Appendix C – Network Standards Organizations The networking industry is ful ards. This appendix will summarize several of the important standards used in the network industry. For additional information, sea

AThis is one of the most common standards in the computing industry, let alone the networking industry. The Ameorganization of industry and bstandards. In the computing in ASCII character set. This is a common code for basic ch mbers. ANSI also is States representa izations like ISO and CCITT (see below).

CCITT The CCITT (Comité Consultatif Internationale de Télégraphie et Téléphonie) is an international organization also known as the International Telegraph and Telephone Consultative Committee. As its name implies, it is responsible for establishing standards for communication. Perhaps the most famous standards are the “V” standards for modems and Faxes.

EIA The Electronics Industries Association (EIA) is a group of American manufacturers of electronic equipment. It is prominent in developing standards for the interface between data processing equipment and communication equipment. Perhaps the most well known standard is the RS-232 standard for serial communication via DB-9 and DB-25 connector.

l of standards and committees making new stand

rch for these organizations on the Internet.

NSI

rican National Standards Institute (ANSI) is an usiness groups who develop trade and communication dustry, it is perhaps best known for the development of the

aracters and nutive on several international organthe United



IEEE The IEEE (Institute of Electrical and Electronic Engineers, Inc.) publishes many standards for electrical and electronic equipment. Since they cover a wide variety of equipment, the IEEE is subdivided into committees. The one that is important to networking professionals is called the IEEE 802.x committee. These standards are used for equipment operating in the Physical and Data link layers of the OSI Model. See Appendix A for a summary of the 802.x sub-committees.

ISO The International Standards Organization (ISO) is responsible for establishing international standards for all services and manufactured product. A major ISO contribution to the network community was the development of the OSI (Open System Interconnection) model. Be careful to not get ISO and OSI confused.

SAG SAG or SQL Access Group is working in conjunction with ISO to develop interoperability standards. As you may guess from its name, its emphasis is on SQL or the Structured Query Language. This is a common platform for transferring data from one database application to another. As long as both are SQL compliant, the data can be smoothly transferred.

Appendix D – How to Register for the Exam


Appendix D – How to Register for the Exam

To Register for the Network+ Exams Register for the Network+ Certification Exam by calling 1-888-895-6116 for Prometric or 1-877-551-7587 for VUE. Tests are given at both Prometric and VUE Authorized Testing Centers. To register via the Internet, go to www.2test.com for Prometric or www.vue.com for VUE.

When you call, please have the following available:

Social Security Number or Testing ID

Two forms of ID (one with photo)

Mailing address and telephone number.

Date you wish to take the test.

Method of payment, credit card or voucher.

The test is available to anyone who wants to take the test. Payment is made at the time of registration, either by credit card, or by requesting an invoice be sent to you or your employer. Vouchers and coupons are also redeemed at this time. Individuals may retake the test as often as they like. Payment must be made each time you take the test. Prices subject to change without notice, and may be obtained by calling Prometric or VUE.



Appendix E – Glossary



Access Method A way of accessing the network.

ACK Acknowledgment message confirming receipt of the data packet.

Active Hub Regenerates or amplifies a signal when it is passed through.

Analog Signal A continuously variable signal, or a circuit or device designed to handle such signals; opposite of digital.

AppleShare The file server on an AppleTalk network.

AppleTalk The Apple networking protocol.

Application Software, program; these three terms are often used interchangeably.

Application Layer The highest layer of the OSI Model, it supplies functions to applications, or computers on the network (nodes), so they can communicate with other applications or nodes.

Application Server A dedicated server for applications.

ARCNet Attached Resource Computer Network

ARP Address Resolution Protocol

Attenuation The signal loss due to the physical properties of copper wire that happens over distance.

AWG American Wire Gauge AWG is the standard that describes wire thickness. The AWG wire number decreases as the wire thickness increases.

Bandwidth The difference between the lowest and highest transmission channel frequencies, usually expressed in cycles per second (Hertz or Hz), or bits per second (bps).



Base I/O Port Address The channel through which data flows between a computer’s hardware (such as a NIC) and the CPU.

Base Memory Address The location in a computer’s RAM of the beginning of the buffer area that is reserved for use by the NIC.

Baseband Uses the entire capacity of the cable as a single channel.

Beaconing A process used to identify any area on the network that may be experiencing problems.

BNC Connector British Naval Connector

BOOTP BOOTstrap Protocol

Boot Prom Boot Programmable Read Only Memory is used on networks that utilize diskless workstations.

Bridge Hardware that connects one network with another.

Broadband Broadband allows two or more channels to share the bandwidth of the cable or medium. The signal flow is uni-directional.

Buffer A bus driver. Can also refer to a class of memory registers and devices that match data transfer speeds between computers and hardware (peripherals). An area of memory that holds information for a peripheral device until it can be processed.

Bus Topology A LAN in which all workstations are connected to a single cable.

Carrier Companies contracted to carry our data over long distances.

Cellular Networking A form of mobile computing.

Class A IP Address IP Address used by very large networks, such as IBM, GM, or DEC.

Class B IP Address IP Address used by medium-sized networks, such as Microsoft; these are all in use at the present time.

Class C IP Address Class C IP addresses are used for smaller networks that do not exceed 254 hosts.



Client User computer “being served” by another computer, called a server.

Client Software Software used by the client.

Clocking The method used by the NIC to count and pace the number of signals that it sends and receives.

Coaxial Cable An electrical cable consisting of a solid piece of metal wire surrounded by insulation, which is, itself, surrounded by a tubular piece of plastic.

Concentrator Same as a hub.

Cooperative Multitasking A form of multitasking, in which it is the responsibility of the currently running task to give up the processor, to allow other tasks to run.

CRC Cyclic Redundancy Check, or Cyclic redundancy Code, is a number derived from, stored, or transmitted with a group of data in order to detect data corruption.

Crosstalk The signal bleed that occurs between individual wires in a cable.

CSMA/CA Carrier Sense Multiple Access with Collision Avoidance

CSMA/CD Carrier Sense Multiple Access with Collision Detection

CSNW Carrier Sense NetWare

CSU/DSU Changes the frame types between the LAN and WAN

Data Information, as recognized by a computer and transmitted across a variety media, from computer or network to another, using a specific protocol, or language.

Data Encryption Data that is encoded for security reasons, at the sender’s level and then decoded at the recipient’s level.



Data Link Layer The Data Link layer is the second lowest layer in the OSI model. It is the last stop before the data packets are placed on the media for transmission. The Data Link layer splits data into frames, which are large areas of data that are split into smaller non-contiguous blocks, for sending on the Physical layer. It also receives acknowledgement frames. It performs error checking and re-transmits frames that were not received correctly.

Default Gateway When you type the IP address of the gateway routers you have installed on your network, whichever one appears first on the list is considered the default gateway.

Demand Priority This access method is designed for the 100 Mbps Ethernet standard 100VG-AnyLAN

DHCP Dynamic Host Configuration Protocol - A method for leasing and maintaining that lease for IP addresses and related information to clients.

Digital Signal Baseband uses digital signals over a single frequency. (Simple “on” or “off” signal.)

Disaster Recovery Being able to recover data from a disaster.

Disk Mirroring The use of two or more hard disks that “mirror” the main one, so that one can take over for the other if it fails.

Disk Striping Also called data striping, this is the dividing into segments of logically sequential data, such as an individual file, so that the segments can be written to multiple disk drives, in a round-robin fashion. If the processor is capable of reading or writing data faster than a single disk can supply or accept it, the second disk can locate the next segment while data is being transferred from the first disk.

DMA (Direct Memory Access)

A limited form of bus mastering, DMA allows a device to read and write memory without intervention by the CPU.

DNS Domain Name System



DSMN DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems.

DUN Dial-up Networking

EISA Bus Extended Industry Standard Architecture is a PC bus that converts the PC bus from 16-bits to 32-bits.

Ethernet A local area network (LAN) recognized as the industry standard.

EtherTalk A way to run AppleTalk on coaxial cable using an EtherTalk NB NIC.

Event Viewer A Windows NT utility that will allow you to log any events and errors.

FAT File Allocation Table

Fax Server A server on a network that is configured to provide both incoming and outgoing fax services to the entire network.

Fiber-Optic Cable Optical fibers carry digital signals in the form of modulated pulses of light.

File Server A network’s central computer, with a very large amount of storage space for shared files.

Firewall A set of programs running on a network’s gateway server that monitors incoming and outgoing traffic and allows only authorized packets to be transmitted or received.

Frame Relay An improved version of X.25 packet switching technology.

Frames A group of bits containing address information, error detection, and other control information, sent over a communications channel.

FTP File Transfer Protocol

Full-Duplex Data can travel in both directions at once.



Gateway A computer that acts as a translator, that enables two networks, using different protocols, to communicate with each other.

GSNW Gateway Service for NetWare

Half-Duplex Half-Duplex can send transmissions both ways (send and receive), but only one at a time.

Header The portion of a packet that contains source and destination addresses, and other information. It precedes the actual data.

HOSTS and LMHOSTS files

Text files that are used to look up and resolve names to IP addresses. HOSTS is used for DNS and LMHOSTS is used for WINS.

HTTP Hypertext Transfer Protocol

HTTPS HyperText Transport Protocol Secure

Hub The center of a cabling system or a network with star topology architecture.

Hybrid Topology A network topology that combines bus, star, or ring topologies.

ICA Independent Computing Architecture

ICMP Internet Control Message Protocol, defined in STD 5, RFC 792, is an extension to the Internet Protocol (IP) that allows for the generation of error messages, test packets, and informational messages related to IP.

ICS Internet Connection Sharing

IFCONFIG Shows the user’s network interface configuration

IMAP4 Internet Messaging Access Protocol

Interoperability The ability of software and hardware to communicate, even though there may be multiple machines from multiple vendors.

IP Internet Protocol

IP Address This 32-bit host address defined by the Internet Protocol in STD 5, RFC 791, is usually represented in dotted decimal notation.



IPCONFIG DOS command that tells you the IP address for your computer.

IPsec A security protocol that works at network layer

IRQ Interrupt Request causes the processor to temporarily suspend normal instruction execution and to start executing an interrupt handler routine.

ISA Bus Industry Standard Architecture refers to the bus architecture used in the IBM PC.

ISDN Integrated Services Digital Network is a set of communication standards that allows a single wire or optical fiber to carry voice, data, and video data sources.

Kerberos A system for user authentication

L2TP Layer 2 Tunneling Protocol

LAN Local Area Network

Laser Transmissions A wireless network standard that uses laser beams for the transmission of data.

Latency The time it takes for a packet to go from sender to receiver, across a network connection.

LLC Logical Link Control – a sublayer of the Data Link Layer

LocalTalk AppleTalk networks are usually called LocalTalk.

MAC Media Access Control – a sublayer of the Data Link Layer. The MAC address is the address that is hard-wired onto the NIC by the manufacturer, it’s “hardware address.”

Mail Server Server used for E-mail.

MAN Metropolitan Area Network

Management Software The primary software package used by the administrator.

MAU/MSAU Multistation Access Unit in a Token Ring network, a device to attach multiple network stations in a star topology, internally wired to connect the stations into a logical ring.



MCA Bus Micro Channel Architecture, a 32-bit bus, introduced by IBM for its PS/2 computer line, totally incompatible with the original PC bus.

Media A method of data transmission.

Media Tester Tool used for testing the continuity and pin-outs of a cable

Mesh Topology Every device is connected to every other device by separate cables and has redundant paths.

MHS Message Handling System – A standard defined by ITU-T as X.400 and by ISO as Message-Oriented Text Interchange Standard (MOTIS). MHS provides the functions for global E-mail transfer among local mail systems, and is used by CompuServe, among others.

Microwave Transmissions

A wireless network standard that uses microwave signals for data transmission.

Multimeter One of the most basic tools for electronic troubleshooting.

Multistation Access Unit A type of hub. The actual ring in a Token Ring network is in the hub.

Multitasking Performing multiple tasks simultaneously.

Narrow-Band Radio Single Frequency Radio. The transmitter and receiver are tuned to the same frequency. Much like your local radio station.

NAS Network Attached Storage

NAT Network Address Translation

NBTSTAT NetBIOS Statistics

NDS NetWare Directory Services

NetBIOS Names used with WINS; protocol as well

Network A group of computers linked together for the purpose of sharing resources.

Network Adapter Card Also known as a network interface card. Provides the physical connection to the network cable.



Network Administrator The individual who has complete responsibility for maintaining a network.

Network Interface Card (NIC)

An adapter circuit board installed in a computer that provides a physical connection to a network.

Network Layer The hardware that is used to construct the network plays an important role at this layer. The network layer handles all the routing information as packets travel from one network to another.

Non-Routable Protocol A protocol that cannot be routed or passed through routers on a network.

NOS Network Operating System

NTFS NT File System

NTSTAT A TCP/IP utility command that will return information regarding the status of a network.

NWLink A Windows NT service that allows for interoperability with the NetWare NOS.

Octet Each part of an IP Address that contains eight bits of data is called an octet.

OSI Refers to the OSI (Open Systems Interface) Model.

Packets A generic term used to describe a unit of data. A “packet” may also refer to a frame or datagram, depending on the protocol. A packet actually refers to Application layer data units (APDU).

Passive Hub Acts as a connection point only.

Password Security A user has to enter a password to gain access to the network or to shared resources.

Patch Cable They extend the connection between the computer and the hub or between two hubs.

PCI Bus A 32-bit architecture bus for PC expansion cards.

PCMCIA Card PCMCIA (Personal Computer Memory Card International Association) cards are credit card sized expansion buses that are used in portable computers (laptops) to provide the same expandability enjoyed by desktop computers, including network connectivity.



Peer-to-Peer All the computers on the network can act as either a client or server, depending upon the needs of the user.

Performance Monitor A software tool that is used to monitor the performance of a network server. Although included as part of Windows NT, many third-party applications are available.

Peripheral A hardware device, such as a printer or scanner.

Physical Layer The Physical layer is the lowest layer in the OSI Model. This layer determines the interface hardware and the medium that will be used to transmit the data from the Data Link layer.

PING A way of testing the server to see if it is alive and functioning, and running on TCP/IP.

Plenum The space between the ceiling and the floor above; used to circulate air through a building.

Port Number Defines a channel between a device and the processor.

POP3 Post Office Protocol 3

PPP Point-to-Point Protocol

PPTP Point-to-Point Tunneling Protocol

Preemptive Multitasking Introduced in version 3.5 of Windows 3.1, this feature has a different scheme called cooperative multitasking, which means that a process can take control of the CPU and check for other processes. The preemptive feature allows NT to hand out slices of CPU time, and even if a process takes full control, other processes will still run.

Presentation Layer The Presentation layer formats data exchange, converting character sets and encrypting data, allowing incompatible processes in the Application layer to communicate with the Session layer.

Print Server Dedicated server for printing.

Protocol Stack A group of protocols that are used to communicate between computers on a network. The OSI model is the ideal protocol stack.



Proxy Server One that serves many clients through only one connection; For example, the user is connecting to the Internet via a secondary source, i.e. the proxy server.

Punch Down Tool Used for “punching” down wire to a block

RAID Redundant Arrays of Independent Disks

RARP Uses a MAC address to find an IP address.

RAS A service provided by Windows NT that allows most of the services provided by a network, including support for dialup and logon, to be accessed via a modem.

Redirector/Requester Redirects a call from one port to another. For example, redirects a print job from the local port to the network printer.

Reflective Infrared The signal is beamed towards a central unit, which then routes the signal appropriately.

Repeater Used to increase cable distances in network environments.

Resources The services or peripherals that are shared over the network.

Ring Speed In Token-Ring networks, the ring speed on the NIC is set to either 4 Mbps or 16 Mbps.

Ring Topology In a Ring topology, the devices are connected in a continuous loop.

RJ-11 Connector Connector used with standard telephone wire. Flat cable with 2 or 4 conductors.

RJ-45 Connector Connector used with UTP and STP network cables. Will hold up to 4 pairs of conductors.

Routable Protocol A protocol that can be routed over the internet or through routers on a network.

Router A device that forwards packets between networks.

SAN Storage Area Network



Satellite Microwave A wireless network that utilizes microwave signals to transmit data.

Scatter Infrared Transmission rates are slower with this type, as the signal is designed to bounce off of walls, ceilings, etc. until it reaches the receiver. The effective distance of the signal is limited to about 100 feet.

SDH Synchronous Digital Hierarchy

Security The system used to protect data on a network from unauthorized use.

Server A computer on a network that provides services to other computers.

Server Software Software that resides on a server.

Session Layer The Session layer handles such things as security authentication, data transfer, acknowledgments (ACK), connection establishment and release.

Sharing Allowing files to be shared from one computer to another.

Shielded Twisted Pair A type of cable in which pairs of conductors are twisted together to prevent possible cross-talk from nearby wiring.

Simplex A uni-directional data channel, as opposed to duplex.

Single-Frequency Radio Narrow-Band Radio Transmission

SLIP Serial Line Internet Protocol, defined in RFC 1055, is software that allows the Internet Protocol (IP), normally used on Ethernet, to be used over a serial link.

SMAU Smart Multistation Access Unit

SMTP Simple Mail Transfer Protocol is used to transfer E-mail between computers, usually over Ethernet.

SNMP Simple Network Management Protocol, the Internet standard protocol defined in STD 15, RFC 1157, was developed to manage nodes on an IP network. SNMP is not limited to TCP/IP.



SONET Synchronous Optical Network

Spread-Spectrum Radio Spread-spectrum broadcasts over a range of frequencies, so it is less susceptible to eavesdropping. This type of transmission is commonly used to connect multiple LAN segments together.

SSL Secure Sockets Layer

Star Topology A LAN topology in which all workstations are wired directly to a central workstation called a hub. If the hub fails, the entire network goes down.

Subnet Mask Using binary addition, a router can determine what addresses are local and what addresses are for other subnets within the network.

Subnetting The process of subdividing a network into logical units.

TCP/IP Transmission Control Protocol over Internet Protocol, the official protocol of the Internet.

TDR Time-Domain Reflectometer – A cable tester.

Terminator A connector that has a built-in resistor in order to absorb signals and eliminate signal bounce.

Terrestrial Microwave A form of microwave communication used for earth-based communication between two buildings, or across large flat open areas, such as bodies of water or deserts.

Thicknet An Ethernet cable variant commonly known as 10base5, that uses a large diameter, rigid coaxial cable with multiple shielding and an impedance of 50 ohms. Maximum segment length is 500 meters.

Thinnet A type of coaxial cable whose maximum segment length is 185 meters.

Throughput The maximum speed that “traffic” can move, measured in Mbps (Megabits per minute).

Token Passing An access method used in a Token Ring topology.

Token Ring A LAN topology that uses an access method called token passing.

TokenTalk A way to run AppleTalk in a Token Ring (IEEE 802.5 Standard) environment.



Tone Generator Connected to the wires at the known location (the room with the outlet), this applies a signal on the wires. The “fox.”

Tone Locator A receiver set to the frequency of the generator. When the receiver is placed in close proximity to the wire that has the signal applied, it will emit a tone, thus locating the wires. The “hound.”

TRACERT Trace Route command in NT allows you to specify a remote host and report back on each subsequent router and the times it takes to traverse those routers in a command line interface. Additionally named traceroute in UNIX environments.

Trailer The part of a data packet that contains the error corrections information.

Transceiver A device that transmits and receives data.

Transport Layer The Transport layer is responsible for packaging (and un-packaging) the data for transport, and for the error-free delivery of the transmitted data.

UDP User Datagram Protocol, defined in STD 6, RFC 768 is a connectionless protocol, which, like TCP, is layered on top of IP.

UNIX A major operating system that is primarily used on minicomputers and has many features that are favored in the engineering and scientific environments.

Unshielded Twisted Pair Twisted network cables that do not have any shielding.

Vampire Tap Connectors that utilize sharp teeth to pierce the cable jacket to make the connection. Used on transceivers.

VLAN Virtual LAN

WAN Wide Area Network

WINIPCFG A command used to display the current configuration of a Windows computer.

Wire Crimper Tool for stripping and cutting wire



WINS SERVER A way for Microsoft hosts to register themselves, resolve and also release the mapping of their network NetBIOS name to an IP address.

Zones A named Subnetwork used for expanding the LocalTalk network or for relieving traffic on a larger network. AppleTalk can incorporate other types of networks, such as Token Ring, using zones



Appendix F – Chapter Review Questions and Answers



The following are the questions found at the end of each chapter along with the correct answers.

Review Questions Chapter 1

1. What is the key difference between a local area network and a wide area network?

A LAN is the basic building block (and smallest) of a network. It is confined to a limited area. A WAN is not geographically limited. A WAN is created by connecting LANs together. LANs typically also have much faster communication speed than WANs.

2. What is the main reason for networking computers?

To share resources, such as data, applications, and peripheral devices.

3. What is a “sneaker net”?

The “old fashioned” way computer users shared resources by taking a file on a floppy disk to the computer that had the services they needed to use. Dragging a printer from computer to computer for users to utilize is another form of a sneaker net.

4. Name some advantages of having centralized documents.

Files are easily accessed by all users. Access can be denied to unauthorized users (security), data backups can be more easily and routinely performed.

5. What does MAN stand for and why is it no longer in use?

Metropolitan Area Networks have been replaced by the Internet.

6. Name some advantages of a Peer-to-Peer network.

Simple to install, configure, and manage (each user manages their own computer) for a small number of workstations (10 or less), inexpensive to install (no need to buy expensive server).

7. Name some disadvantages of a Peer-to-Peer network.

No security, loss of performance occurs if expanded over 10 workstations. Workstations need to be close together (in a relatively small area, like one office).



8. Name some advantages of a Server-based network.

Centralized location of resources (server). File and resource security available to limit unauthorized access. Ease of data backups. Can be expanded as network grows. Centralized administration. Increased performance on large networks.

9. Name some disadvantages of a Server-based network.

Expensive to install (will need to purchase expensive server). More difficult to install and configure, more difficult to manage (needs an administrator).

10. Name the three basic topologies.

The three basic topologies are: Bus, Star, and Ring.

11. What is the difference between a physical and logical topology?

Physical topologies are the actual wires and hardware that we can see. They represent what the topology looks like. Logical topologies represent the way that a networks functions.

12. Name two media access methods

The access methods are CSMA/CD CSMA/CA, Token Passing, and Demand Priority.


1. What is the difference between an operating system and a network operating system?

Network operating systems are specialized operating systems designed to function in a network environment. Some NOSs function as the operating system that runs a computer’s stand-alone functions as well as its network interfaces.

2. What is the difference between preemptive and non-preemptive multitasking?

Multitasking means that a computer has the ability to perform more than one task at a time. Preemptive multitasking means that the operating system can take control of the processor without a task’s permission. Non-preemptive multitasking is when the task decides when it is done with the CPU.



3. What is the purpose of the redirector?

The redirector (in Novell NetWare it is called the requester) forwards requests away from the local bus, redirecting them to the server. The purpose of the redirector is to make network resources look like local resources to the application.

4. NetWare is designed as an operating system that will overlay _____________ environments.

NetWare is a reliable operating system that provides excellent performance and security. It is designed as an operating system that will overlay multi-operating system environments.

5. What is NDS?

NDS (NetWare Directory Services) is the core of the NetWare operating system. It is a hierarchically organized database that provides security, name service, messaging, routing, web-publishing, management, and file and print services. Organization of network resources such as users, groups, servers, and volumes is also handled with NDS.

6. What are the minimum hardware requirements for installing Novell NetWare version 5?

Pentium Class or Higher CPU, 64 MB RAM, 550 MB of free hard drive space.

7. Define interoperability.

Interoperability describes the ability of an operating system to interact with other operating systems.

8. Unlike NetWare, Windows NT combines the _____________ and the ___________________ into one.

Windows NT combines the operating system and the network operating system into one.

9. What is NTFS?

NTFS is the file system in Windows NT and it must be utilized in order to take full advantage of NT’s security features.




NT uses domains in order to accomplish its security goals. A domain is simply a group of workstations with a shared security database.

11. What are the minimum hardware requirements for Windows NT Server?

476DX-3 CPU, 16 MB RAM, 125 MB free hard drive space.

12. Name some of the services and protocols that Microsoft included with Windows NT to ensure interoperability with NetWare.

NWLink is a protocol based on Novell’s IPX/SPX and is used for communication between the two systems. GSNW (Gateway Services for NetWare) provides the gateway between an NT domain and the NetWare server. CSNW (Client Services for NetWare) allows NT workstations to use file and print services on a NetWare server. FPNW (File and Print Services for NetWare) allows NetWare clients to access NT file and print services. DSMN (Directory Service Manager for NetWare) is used to integrate user and group account information between NT and NetWare. Migration Tool for NetWare is used to convert NetWare accounts to NT.

13. What OS is similar to UNIX and is a publicly open system?

Linux

14. What type of computer was developed by Apple computer in 1984?

The Macintosh

15.What type of network would utilize Windows for Workgroups as an operating system?

Windows for Workgroups is a version of Windows 3.1 that includes the ability to run a peer-to-peer network.

Review Questions Chapter 3 1. Who developed the OSI model?

The OSI model was developed by ISO (International Organization for Standardization).

2. Name the seven layers of the OSI model.

Application, Presentation, Session, Transport, Network, Data Link, and Physical

3. A network adapter card operates at the _______ layer of the OSI model

Network layer



4. A bridge operates at the ________ layer of the OSI model.

Data Link layer

5. A router operates at the _________layer of the OSI model.

Network Layer

6. Data compression takes place at the __________ layer of the OSI.

Presentation layer

7. Which OSI layer is responsible the MAC address?

The Data Link layer

8. What is the function of the Application Layer?

The Application layer is responsible for communication between a user’s application and the network. This is not the actual application or program, simply a support layer that allows an application to use the network by acting as a translator.

9. The ____________ layer is responsible for the mechanical and electrical functions of transmitting data over a network.

Physical

10. What is the function of the Presentation Layer?

The Presentation layer is the translator for the network. It translates data into a format that is compatible with the network and back into a format that is compatible with the computer.

11. Which OSI layer is responsible for establishing, managing, and ending connections?

The Session layer

12. What is a MAC address?

The MAC address is another name for the 12-digit (6-byte) hexadecimal address that is hardwired on the NIC by the manufacturer. It is a computer’s physical address.

13. Which part of this MAC address is the Device ID?

D3-B4-01

14. Which OSI layer makes routing decisions?

The Network layer



15. Which OSI layer is responsible for delivering data in sequence, without duplication and error free?

The Transport layer

16. The Data Link layer has been split into two sub-layers. What are they?

The Logical Link (LLC) layer and the Media Access Control (MAC) layer

17. What is the function of a Gateway?

A gateway translates between two networks that use different protocols. A computer with special software serves as a gateway and allows for communication between completely dissimilar networks.

18. Which IEEE standard defines the Logical Link Control (LLC) sub-layer?

802.2

19. What are NDIS and ODI?

They are Network Adapter Card interface specifications. They are incompatible with each other. NDIS (Network Driver Interface Specification) was co-developed by Microsoft and 3Com, while ODI (Open Data Link Interface) was co-developed by Novell and Apple. The purpose of these standards is to allow operating system vendors to write multiple drivers for the same NIC. This way more than one protocol can be bound to a single NIC.

20. Describe protocol binding.

In order to function, a protocol must be bound to the NIC. This binding process is what links the protocol stacks to the NIC driver. It is possible to bind two protocols the one NIC (such as TCP/IP and IPX/IPX) or to have two NICs with one protocol bound to each one. The order in which these protocols are bound to the NIC determines which one the network operating system will attempt to use first.

21. Which is faster, connection-oriented communication or connectionless communication?

Connectionless communication is faster, but connection-oriented communication is more reliable.

22. . Name as many routable protocols as you can remember.

AppleTalk, DECnet, IPX/SPX, PPP, PPTP, SLIP, SMB, SNA, TCP/IP, UDP, X.25, XNS

23.. You have expanded your NetBEUI network into two segments and are using an intelligent router to optimize network traffic. Will this work? Why or Why not?



No, NetBEUI is a non-routable protocol.


1. What is the maximum segment length of Thinnet?

185 meters

2. What is the maximum segment length of Thicknet?

500 meters

3. What type of connectors are used with Coaxial cable?

BNC connectors

4. What is the purpose of a transceiver?

A transceiver is a device that both transmits and receives data on a network.

5. How is a vampire tap connected?

They utilize sharp teeth that puncture the cable to make the connection.

6. What is the purpose of plenum cabling?

Plenum grade cabling is used in the plenum (the space between the ceiling and the floor above, which is used to circulate air in a building). Fire codes usually call for special cable in this area because PVC cable gives off poisonous gas and fumes when burned, which would end up being circulated throughout the building.

7. What is the maximum segment length of UTP?

100 meters

8. What is the transmission speed of category 5 cabling?

Up to 100 Mbps



9. What is the most popular of the cable types?

UTP is the less expensive of the twisted pair cable types. It is also flexible and easy to install, making it the most popular cable type.

10. Which twisted pair cabling is less sensitive to EMI?

STP is insulated with a foil mesh between the wire pairs, which results in less sensitivity to EMI and crosstalk.

11. What type of connector is used with twisted pair cable?

RJ-45 connectors

12. What is the most expensive cable type?

Fiber-Optic cable is the ideal cable type for networking. However, it is the most expensive and most difficult to install.

13. What is the least expensive of the cable types?

UTP is the least expensive of the cable types. It is also flexible and easy to install, making it the most popular cable type.

14. List some advantages of fiber-optic cable.

Fiber-optic supports extremely high bandwidths, segment lengths of up to several miles, and it is not subject to EMI or eavesdropping.

15. What does AWG stand for and what is it?

American Wire Gauge (AWG) is the standard that describes wire thickness. The AWG wire number decreases as the wire thickness increases.

16. Describe baseband.

Baseband uses the entire capacity of the cable as a single channel.

17. Describe broadband.

Broadband allows two or more channels to share the bandwidth of the cable, making the signal flow unidirectional.

18. What is the difference between simplex, half-duplex, and full-duplex communication?

Simplex communication is one way, can receive but not send. For example, a pager. Half-duplex communication can send or receive, but not at the same time. For example, a CB radio. Full-duplex can send and receive signals at the same time. For example, the telephone.



19. What is the function of a network adapter card?

Network Adapter Cards or Network Interface Cards (NICs) are used to connect the computer to the network. (They make the physical connection to the network.) NICs translate the data that computers can understand into signals that can be transmitted over the network medium and back again.

20. In Token Ring networks, what are the two ring speeds available?

In a Token Ring network if the correct ring speed is not selected a computer will not be able to connect to the network. The two choices available are 4 Mbps and 16 Mbps.

21. Where would you expect to find a PCMCIA card?

PCMCIA (Personal Computer Memory Card International Association) cards are credit card sized expansion buses that are used in portable computers (laptops) to provide the same expandability enjoyed by desktop computers, including network connectivity.

22. What are some of the reasons you would need to install a wireless network?

To create a temporary network, to backup a cable-based network, to provide a mobile network environment, for areas where running cable would be impossible or unsightly, outdoor installations and to connect to remote sites such as a ship or oil platform.

23. What are the four basic wireless transmission types?

Infrared, Laser, Radio, and Microwave

24. Which is the most secure type of radio wireless network?

Spread-Spectrum Radio is more secure than Single-Frequency Radio (Narrow-Band Radio) because it broadcasts over a range of frequencies instead of just one.

25. Which microwave transmission type is used to transmit globally?

Satellite microwave is used to transmit globally; Terrestrial microwave is used to transmit over shorter distances.


1. What are the three primary access methods?

CSMA/CD & CSMA/CA, Token Passing, and Demand Priority



2. Describe the difference between the two different contention methods CSMA/CD and CSMA/CA.

CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection and CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance. Both CSMA/CD and CSMA/CA listen to the network cable to determine if it is free (Carrier Sense), if no data is traveling, a CSMA/CD computer will transmit. If there is another computer on the network that transmitted at exactly the same time, a data collision will occur, and both sets of data will be destroyed. CSMA/CD detects that a collision has occurred and waits a specified amount of time before re-transmitting. With CSMA/CA the process is much the same except that instead of just transmitting when it senses that the cable is free, it will send a signal that it is about to transmit. This will cause any other computer that was about to transmit to wait and so data collisions are avoided. This extra step can slow down network traffic, so CSMA/CA is not the most popular of the two contention methods.

3. Why isn’t token passing considered a contention method?

A computer on a token passing access method network must possess the token in order to transmit data. Therefore, only one computer at a time will transmit in this kind of architecture, and so, no contention.

4. Describe how data is transmitted in Token Ring architecture

A token, which is a special kind of packet, is circulated around the ring from computer to computer in a Token Ring network. A computer that wants to send data onto the network waits until the token is passed to it and takes possession of it. The transmitting computer encodes the token with the data that it wants to transmit, as well as header and trailer information that contain the destination and source addresses, as well as error control information. It then passes the token back out onto the ring where it travels on until it reaches the destination computer. The destination computer copies the data into its buffer and adds some acknowledgment information (or re-transmittal information if it detected errors) and releases the frame back out onto the network where it travels back to the source computer. Assuming that the data was transmitted error-free, the source computer removes the “used” frame from the network and creates a new “free” token to release back out onto the network.



5. What happens if two computers using the demand priority access method transmit at exactly the same time?

If the hub receives two transmissions at exactly the same time the one with the highest priority is processed first. If the two transmissions have the same priority level, they are processed at the same time by alternating between the transmissions.

6. How is data transmitted over the network cable?

In packets or frames. (Small chunks of data at a time.)

7. What is CRC and what part of the packet is it usually located in?

CRC (Cyclical Redundancy Check) is a mathematical calculation that is calculated at the source computer and included in the trailer of the packet. When data arrives at the destination computer, the calculation is redone and if it calculates as it did at the source computer it is assumed that the data arrived intact.

8. What sort of information do packet headers contain?

The header contains information such as an alert signal that announces that data is being transmitted, the source and destination addresses and clocking information.

9. What does the “T” in 10BaseT indicate?

The first part indicates transmission speed (10 means it transmits at 10 Mbps), the second part “Base” indicates that it uses baseband (single channel) technology and the last part indicates the cabling type, or maximum segment length in the case of coaxial cable. (“T” indicates Twisted-pair).

10. What is the maximum segment length in 10Base2?

185 Meters. The “2” in this case means 2 times 100 meters, but in the case of Thinnet coaxial cable the maximum segment length is 185 meters.

11. What type of connectors are used in 10Base5?

BNC connectors

12. What type of cable is used in 10BaseFL?

Fiber-Optic

13. Name the two main 100 Mbps Ethernet Standards.

100VG-AnyLAN, also called 100BaseVG, VG, and AnyLAN. The VG stands for Voice Grade. 100BaseX is sometimes called Fast Ethernet. It has different specifications depending upon the type of cabling used (hence the “X” in the area that indicates cable type).



14. Which IEEE Specification defines Ethernet?

The IEEE 802.3 standard

15. Which IEEE Specification defines Token Ring?

The IEEE 802.5 standard

16. What are the two transmission speeds of Token Ring?

4 Mbps and 16 Mbps

17. How are data collisions avoided in the Token Ring architecture?

A computer must posses the token in order to transmit data. Since no other computer can transmit while one computer has the token, data collisions are avoided.

18. Describe beaconing as it applies to Token Ring architecture.

The active monitor (which is the first computer to go online) is responsible for monitoring network activity to make sure that frames are being sent and received accurately. It also ensures that only one token is traveling the ring at a time and investigates any frames that have traveled around the ring more than once. It does this by transmitting a signal every seven seconds. This signal is called beaconing and it travels from computer to computer. If a computer doesn’t receive an expected signal from its upstream neighbor it will notify the monitor that a problem may exist.

19. Which way does data travel in a Token Ring network?

Which way data travels in a Token Ring network is a matter of convention. IEEE 802.5 says it travels clockwise, while IBM says that it travels counter-clockwise. It can be either depending upon how it is set up. The main thing is that data only travels in one direction on a Token Ring network. It is more commonly set up to travel clockwise, however.

20. What is a SMAU?

SMAU stands for Smart Multistation Access Unit. This is a hub that has all of the features of an active hub (regenerates or amplifies the signal) with additional capabilities such as certain network management functions. A SMAU may have the capability to shut down a connection that is producing errors thereby allowing the rest of the network to function.

21. Describe a MIC connector.

MIC (Media Interface Connectors) are connectors that have neither male nor female ends. Any connector can be connected to another MIC connector. They are also called hermaphrodite connectors.



22. How does a computer on a LocalTalk network obtain its address?

When a computer first comes online in a LocalTalk network it randomly selects an address from a range of allowable addresses. It then broadcasts the address to determine if any other computer on the network is using it. If no other computer is using the address, it stores it to use each time it connects to the network.

23. What is the purpose of AppleShare?

AppleShare is the name of the file server on an AppleTalk network. It also provides a print server.

24. What type of access method is utilized by an ARCNet network?

Token-passing.

25. How does data flow in an ARCNet network?

The token is passed around the network in numerical order. It first goes to computer #1 and then #2, etc. It does this even if computer #1 is at the opposite end of the network from computer #2.


1. What are the two tools required to initiate a network design?

All you need to start a network project is a pencil and some paper.

2. What are the two areas of concern when starting a network project?

You will need to consider the customer and the network goals.

3. What are the two most prominent reasons to choose a peer-to-peer network?

The best reasons for using peer-to-peer are its simplicity and low cost.

4. What is the number one reason for choosing a client/server network?

The number one reason for using a client/server network is security.

5. Is NetBEUI a good protocol to use with a large WAN?

No, NetBEUI is a non-routable protocol and will not interface with routers.



6. Your client is installing a small Ethernet network and trying to save money at the same time. However, he intends to expand the network in the future. Give one reason why you should recommend that he spend a little more now and install CAT 6 cabling instead of CAT 5.

It will be less costly to install CAT 6 now than to replace the CAT 5 later when the network needs to be upgraded from 100 Mbps to 1 Gbps to handle the higher traffic.

7. You are expanding your network and will need to invest in 50 to 100 new network cards. Your accounting office found a really good deal on network cards, but they are not all the same. Why should you refuse this offer?

First, you cannot be sure that they will meet the specifications of your network. Also, having to maintain a variety of network cards will increase the workload of your IS department – it is better to standardize network cards in a large network.

8. Your company just bought ten new computers and all are guaranteed to meet the minimum requirements of Windows XP. Was this a good purchase?

No – the minimum requirements are just enough to run the NOS, but not enough to run it efficiently.

9. How do you know if a new piece of hardware will work with Windows XP?

Check the Windows Catalog on the web at www.microsoft.com/windows/catalog.


1. What is the difference between a hub and a MAU?

Hubs are used with Ethernet networks and MAUs are used with Token Ring networks.

2. What is the difference between an active hub and a passive hub?

Active hubs are used to connect nodes and boost the signal strengths. An active hub requires some input power. Passive hubs are used only to make connections.



3. Define a repeater, a bridge, a router, and a gateway.

Repeater - A repeater is a device that is used to extend the cable lengths of a network segment. They do not translate or filter any information. They do however, amplify the signal thereby compensating for signal loss due to long cables. Repeaters work in the Physical layer of the OSI model.

Bridge - A bridge does the same things as a repeater but has one additional feature. A bridge can be used to isolate segments on a LAN, thus reducing the traffic for each segment. Bridges work in the Data Link layer of the OSI model.

Router - A router has all the features of a bridge, but it can switch packets across multiple networks. They can also determine the best path for “routing” traffic and filter broadcast traffic to the local segment. Not all network protocols will work with a router. For example, NetBEUI is not routable.

Gateway - Gateways make it possible to connect different network architectures. Think of a gateway as a computer that acts as a translator between two networks that don’t speak the same language.

4. What is analog communication?

Analog communication is based on PSTN or public switched telephone network.

5. A form of digital line that is capable of 1.544 Mbps transmissions is called?

T1

6. Name three advanced WAN environments.

Frame Relay, ISDN, and SONET

7. What are the two components of remote network accessing?

RAS (remote access server) and DUN (dial up networking).

8. Name three RAS protocols.

SLIP, PPP, PPTP and L2TP

9. Name four forms of RAS security.

Auditing, Callback Security, Security host, and PPTP filtering.

10. Describe the difference between BAUD and bps.

BAUD rate is the number in cycles per second of the carrier signal of a modem. BAUD is limited to 2400 bps. A bps or bit per second is the actual data transmission rate of a modem. In older modems, BAUD and bps were the same thing.




1. What are the four layers that make up the TCP/IP protocol suite?

The four layers of TCP/IP are: Application, Transport, Internet and Network Interface.

2. How many primary protocols are used to make the TCP/IP Suite?

There are five primary protocols: they are – TCP, UDP, IP, ICMP, and ARP.

3. Name three of the five other protocols used within TCP/IP

Additional protocols are: POP3, SMTP, FTP, SNMP, and HTTP.

4. What is the purpose of DNS?

The Domain Name System is used to resolve host names into IP addresses.

5. What is an FQDN and give an example?

FQDN is a Fully Qualified Domain Name. An example is HTUhttp://www.microsoft.comUTH.


A domain is a group of computers that share a common general purpose.

7. Who is responsible for maintaining top-level domains?

The InterNIC (Internet Network Information Center) is responsible for top-level domain names.

8. Which of the name resolution services will work only in Windows?

WINS

9. IPv4 addresses consist of a ______ bit number.

32

10. What is the value of the leading bit (one on the far left) for a Class A IP address? Class B? Class C?

Class A 01-126 (leading bit is 0)

Class B 128-191 (leading bit is 1)

Class C 192-223 (leading bits 11)



11. Subnetting is the process of breaking an IP address into _________ and ________ groups

Subnetting is the process of breaking an IP address into Umeaningful U and UmanageableU groups.

12. What are five reasons to use subnetting?

Connect physically remote local networks

Connect a mix of network technologies (Ethernet and Token Ring)

Allow an unlimited number of hosts to communicate

Reduce network traffic by limiting broadcast and local traffic to a single segment


1. You are the manager of a large network and have been getting complaints about the system being slow. What kind of software package can you purchase to help analyze your network?

Network Management Software is used to analyze network traffic and network status.

2. In order for your new network management software to monitor the activities of the entire network, each device will need to be _________ compliant.

SNMP (Simple Network Management Protocol)

3. TCP/IP provides several tools that you can use to validate the statistics of your network. List as many as you can.

Event Viewer, ROUTE, NBTSTAT, NETSTAT and TRACERT.




1. What are the two requirements of user level logon?

The user must type in a Username and a Password.

2. In a share level model, passwords are assigned to __________.

Resources

3. What is the function of a firewall?

A firewall is used to prevent unauthorized access to your network from outside via the Internet. It can also be configured to prevent unauthorized transmissions from leaving your network.

4. The acronym RAID stands for____________?

Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks.

5. What are the three most common levels of RAID?

RAID 0 Non-redundant striped array

RAID 1 Mirrored arrays

RAID 5 Striped array with parity

6. What purpose does encryption play in your security model?

Encryption encodes a message so that it cannot be read if it is intercepted during transmission.




1. What are the three primary steps to take when troubleshooting?

The three steps to troubleshooting are: Define the Problem, Isolate the Problem, and Repair the Problem.

2. After repairing a problem, are you finished with the troubleshooting process?

NO – You still need to confirm the repair and document the problem and solution.

3. You are troubleshooting a cable problem. You have found the cabinet with the patch panel and hub, but need to know which of the 50 cables goes to the accounting office. What would be the best tool to help you locate the cable in question?

The best tool for isolating a single cable from many is the tone generator or tone locator. The fox and hound.

4. You have located the cable in question #3, and think it might be shorted. What tool would you need to find the short?

TDRs (Time-Domain Reflectometers) are used to locate shorts in cables.

5. You are working with a TCP/IP network and want to confirm the protocol stack in a specific workstation. What utility can you use to confirm the protocol stack is good?

PING the loopback IP.

6. What is the loopback IP address?

127.0.0.1

7. You need to know the IP address of a workstation. What TCP/IP utility can you use to find the IP address of the workstation?

You can use IPCONFIG from a DOS prompt or if using Windows, WINIPCFG from the RUN command.

8. You have just connected a workstation to the network. What is the easiest way to tell if the network card can “see” the network?

If the network card has indicator lights, you should see the green light that indicates that the network card has detected the presence of a network.



9. What is the difference between bandwidth and throughput?

Bandwidth is the amount of traffic that a network can handle at a given time. Throughput is the maximum speed that a message can be transmitted.

10. You have a Windows 2000 network and received complaints that the server is running slow. What utility can you use to determine the performance of the server?

Performance Monitor



Index

1

100BaseX, 136 100VG-AnyLAN, 136 10Base2, 135 10Base5, 135 10BaseFL, 135 10BaseT, 135

A

access method, 128 Active Directory, 59 active hubs, 41 Address Resolution Protocol, 87 Analog, 109 AppleShare, 142 AppleTalk, 142 Application Layer, 68 application server, 31 ARCNet, 143 ARP, 87 ATM, 186 attenuation,78 attributes, 54 AUI connector, 87 AWG, 106

B

backbone, 33 backup utility, 246 Bandwidth, 106 Banyan VINES, 60 base 106 Beaconing, 139 binding, 83 BNC, 97 Boot Prom’s, 300 Boot Sector, 251 BOOTP, 211 BRI, 186 bridge, 78 Broadband, 106

Broadband Optical Telepoint, 117 brouter, 79

C

Carrier Sense Multiple Access with Collision Detection (CSMA/CD, 38,128

Carriers, 180 Category 3, 80 Category 5,136 Cellular Networking, 118 Change, 57 Circuit-switched, 184 Class A, 215 Class B, 215 Class C, 215 client software, 52 Client Software, 52 clients, 31 Clocking, 109 cloud, 88 coaxial cable, 97 Computer compatibility, 171 connection-oriented, 83 continuity, 263 CSMA/CD, 38,80 CSNW, 59 CSU/DSU, 181 Cyclical Redundancy Check (CRC), 139

D

Data Link Layer, 58 Data Protection, 40 DECnet, 85 demand priority, 129 DES (Data Encryption Standard), 250 Differential backup, 246 Digital, 97 Direct Memory Access (DMA), 99 DLC, 88 DMA, 110 domain, 58 domain controller, 58



Domain Name Service (DNS), 209 Domain Reflectometer (TDR), 265 DSMN, 59 Dynamic Host Control Protocol

(DHCP), 211

E

EES, 251 EISA, 113 EMI, 164 environment, 29 Ethernet, 38 EtherTalk, 142 Event Viewer, 235

F

Fast Ethernet, 39 FAT, 57,303 fault tolerance., 246 FDDI - Fiber Distributed Data, 186 fiber-optic, 103 File Infectors, 251 fire codes, 106 firewall, 244 FPNW, 59 Frame Relay, 184,303 FTP, 74 Full backup, 246 Full Control, 57 Full-Duplex, 106

G

gateway, 79 gateways, 79 Gateways, 179 Gigabit Ethernet, 136 ground probe, 263 Group policies, 59 GSNW, 59

H

Half-Duplex, 106,304 headers, 132 Headers, 132

HOSTS file, 211 HTTP, 207 HTTPS, 207 hubs, 40 hybrid topologies, 35

I

I/O port number, 111 IBM cabling, 103 IBM Type 3 UTP, 140 ICA, 193 ICMP, 90,206 ICS, 212 IFCONFIG, 287,304 IMAP4, 206 Incremental backup, 226 Infrared, 116 Institute for Electrical and Electronic

Engineers, Inc. (IEEE), 80 Internet Control Message Protocol, 206 Internet Protocol (IP), 86 interoperability, 58 IP, 205 IP address, 214 IPCONFIG, 237 IPsec, 192 IPv6, 217 IPX, 85 IRQ, 111 ISA, 113,305 ISDN, 186

K

Kerberos, 193

L

L2TP, 193 LAN, 30 Laser, 116,245 LAT, 88 Layer Two Tunneling Protocol, 193 Linux, 60 LLC, 71 LMHOSTS, 211 LocalTalk, 142



logical topology, 35 LSL, 85

M

Macintosh, 61 Macro Virus, 252 Managing User Accounts, 52 MAU, 140,305 MAUs - Multiple Access Units, 140,305 media access methods, 38 Media Compatibility, 171 Media Tester, 263 mesh topology, 35 MHS, 55 MIB (Management Information Base),

233 MIC (Media Interface Connectors), 140 Microwave, 118 MLID, 85 modem, 188 MSAU, 40,305 Multimeter, 263 multitasking, 48,306

N

NAT, 212 NBTSTAT, 288 NCP, 85 NDIS, 82 NDS (NetWare Directory Services), 54 NetBEUI, 89 NETBIOS, 89 NETSTAT, 235 NetWare, 54 NetWare Client32 for DOS, 56 NetWare Client32 for Macintosh, 56 NetWare Client32 for OS/2, 56 NetWare file server, 54 NetWare Print Services, 55 NetWare security, 54 Network Adapter Cards, 109 Network Layer, 70 Network Neighborhood, 49 Network standards, 134 Network Time Protocol (NTP), 87 Network-attached storage (NAS), 248

NFS, 87 No Access, 45 NOS – Network Operating System, 47 NSLOOKUP, 237 NTFS, 49,307 Null-Modem, 190 NWLink, 86

O

ODI, 82 Open Systems Interface or

Interconnection (OSI), 67 operating system, 47 OS/2, 51

P

Packet switching, 88 Packet-Radio Networking, 118 packets, 75 parallel communication, 109 passive hub, 40 Passwords, 241 Patch Panel, 102 PCI, 113 PCMCIA, 113 peer-to-peer, 32 Peer-to-peer LANs, 49 PGP, 251 physical topologies, 35 Ping, 237 PING, 237 plenum, 106 PPP, 90,192 PPTP, 90,192 Preemptive multitasking, 48,308 PRI, 187 protocol, 38 protocols, 38 proxy server, 212 Punch Down Tool, 250

R

Radio, 117 RAID, 245 RARP, 237



Read, 57 redirector, 53 Reflective Infrared, 117 relative humidity, 164 Remote Access Server or RAS, 190 removable disks, 245 removable optical disk, 245 repeater, 178 requester, 53 ring topology, 34 RIP, 87 ROUTE, 235 router, 78 routers, 78 RPC, 90 RSA, 250

S

SAP, 86 Satellite Station Networking, 118 Scatter Infrared, 310 SDH, 187 security, 310 Security, 310 segment, 33 serial communication, 109 Server room, 164 Server Software, 52 server-based network, 31 Server-based network, 31 servers, 31 sharing applications, 29 signal bounce, 33 Simple Network Management Protocol

(SNMP), 207 Simplex, 106 SLIP, 90,191 SMAU, 140,310 SMB, 86 SMDS, 187 SMTP, 87,207 SNA, 86 sneaker net, 29 SNMP, 90,207 Software analyzers, 265 SONET, 187 SPX, 85

SSL, 193 Standards, 80 star topology, 34 Storage Area Network (SAN), 248 STP, 101 Subnetting, 219

T

tape backup, 245 TCP, 86,204 Telnet, 87 terminator, 311 thicknet, 97 Thinnet, 97 throughput, 273 TLS, 193 token passing, 38 token ring, 35 topology, 33 TRACERT, 235 Trailer, 132 transceiver, 99 Transport Layer, 69 Trivial File Transfer Protocol (TFTP),

87 Trojan Horses, 252 troubleshooting, 257 trunk, 33 twisted-pair, 100

U

UDP, 86,205 UNIX, 59 User Datagram Protocol (UDP), 86 UTP, 101

V

vampire taps, 100 virtual connections, 76 Viruses, 251 VLAN, 185 VPN’s (Virtual Private Networks), 250



W

UWANU, 30 Windows 2000, 50 Windows 95/98, 49 Windows for Workgroups, 137 WINS, 210 Wire Crimper, 262 Wireless, 19, 36

wireless network, 36 Wireless NICs, 112 workstation, 31

X

X.25, 88 XDR, 90 XNS, 88

Documents

Network