Networking Fundamentals

Networking 101

What is a network?

A network can be 2 or more devices connected together to share hardware or software, usually sharing the same media/topology, protocol and a client software or service

Local Area Networks

A local area network (LAN) is a collection of computers located in a relatively small area and connected by a common medium.

The pattern in which computers in a LAN are connected is called the topology.

LAN topologies include bus, star, and ring.

Wide Area Networks

Half-Duplex and Full-Duplex Communications

Backbone Network

TopologiesIn this section we will look at the different

topologies used today

Recognizing Different TopologiesRecognizing Different Topologies

-Star--Star--Bus--Bus-

-Mesh--Mesh--Ring--Ring-

Star Topology

A star topology is a group of computers connected at a central location such as a hub or switch.

The failure of one PC will not effect the network.

Bus Topology

In this configuration all PC’s are connected (daisy chained) by one coaxial cable using

terminators and T connectors. If one node fails then everything before that node falls off the

network.

Mesh Topology

In this configuration all PC’s are connected to everything on the

network simultaneously (Redundancy).

Ring Topology

A ring topology looks like a star topology but the technology used is different. Token passing is used allowing only one message at a time to

be sent to avoid collisions.

Networking Technologies

IEEE(Institute of Electrical and Electronics Engineers)

In February of 1980, this institute developed a set of standards called

the 802 project. This project was built to standardized networking technologies for past present and

future.

Networking Technologies

Ethernet(802.3)

The internet operates using Ethernet technology . It was developed by Xerox and has been defined as

802.3 by IEEE. Ethernet is used in the Star and Bus topologies.

Networking Technologies

Wireless(802.11)

There are 2 commonly used wireless standards.

802.11b – 11Mbps802.11g – 54Mbps

Both technologies use a 2.4GHz radio wave band and are used in the Star topology.

Cable Standards

Speed, Length and Cable Type

10Base-T = 10Mbps, 100 meters, Twisted Pair

100Base-T = 100Mbps, 100 meters, (TP)1000Base-T = 1000Mbps, 100 meters,

(TP)

Coaxial Cable

Coaxial Cable Types

  RG-8 RG-58

Application Thick Ethernet

Thin Ethernet

Thickness 0.405 inch 0.195 inch

Connector Type

N BNC with a T-fitting

Cable Category’sThe category of a twisted-pair cable indicates the

tightness of the twist applied to each pair of wires with-in a cable. The twist help prevent EMI and crosstalk. The tighter the twist the

faster the speed.

UTP Cable Grades

EIA/TIA Grade Applications

Category 3 Voice-grade telephone networks, 10-Mbps Ethernet, 4-Mbps Token Ring, 100Base-T4 Fast Ethernet, and 100Base-VG-AnyLAN

Category 4 16-Mbps Token Ring

Category 5 100Base-TX Fast Ethernet, Synchronous Optical Network (SONET), and Optical Carrier (OC3) Asynchronous Transfer Mode (ATM)

Category 5e or higher 1000Base-T (Gigabit Ethernet)

Standard 10-Mbps Ethernet Specifications

Designation Cable Type Topology Maximum Length

10Base5 RG-8 coaxial Bus 500 meters

10Base2 RG-58 coaxial Bus 185 meters

10Base-T Category 3 UTP

Star 100 meters

Fiber Optic Inter-Repeater Link (FOIRL)

Multimode fiber optic

Star 1,000 meters

10Base-F Multimode fiber optic

Star 500–2,000 meters

Fast Ethernet (100 Mbps) Specifications

Designation Cable Type Topology Maximum Length

100Base-TX Category 5 UTP Star 100 meters

100Base-T4 Category 3 UTP Star 100 meters

100Base-FX Multimode fiber optic

Star 412 meters

Gigabit Ethernet (1,000 Mbps) Specifications

Designation

Cable Type Topology Maximum Length

1000Base-T Category 5 or 5E UTP

Star 100 meters

1000Base-LX

Various multimode fiber optic

Star 550–5,000 meters

1000Base-SX

Various multimode fiber optic

Star 220–500 meters

1000Base-LH

Singlemode fiber optic

Star 10 kilometers

1000Base-ZX

Singlemode fiber optic

Star 100 kilometers

1000Base-CX

150-ohm copper Star 25 meters

Cable Standards

Newest Technologies use Fiber, 10G Standard

10GBase-SR = 10Gbps, 82 meters, Fiber10GBase-LR = 10Gbps, 10 kilometers, Fiber10GBase-ER = 10Gbps, 40 kilometers, Fiber

Media ConnectorsRJ-11 = Standard phone jack connector consisting of 2

pairs of wires.

RJ-45 = Common Ethernet cable connector. Used to connect network devices together for communications

and contain 4 pairs of wires.

Cable Standards

Patch Cable

A patch cable is a straight through cable that relies on a switch or hub to cross the send and

receive wires.

Crossover Cable

A crossover cable is used for a direct connection when no hub or switch is used. It looks identical to a Patch cable except that pins (1 and 3) and (2 and 6) are crossed (Send and Receive wires).

Network Components

HubsA hub is a device that has multiple ports which many

connections can be made. Hubs bear no real intelligence and are generally used to simply connect

segments of networks together.

Network Components

SwitchesA Switch looks similar to a hub but has intelligence. A switch controls traffic by learning its environment and

more effectively transmitting data to decrease network

traffic.

Network Components

RouterA router is a device that forwards traffic from one network

to another, this makes the internet possible. When a router receives a message it determines if it belongs to its network and either receives or sends it on. It is also known as a Gateway meaning that it can translate data

from one format to another.

Network Components

FirewallA firewall is a software or hardware system that separates a computer or

network from one another. Firewalls are used to filter data coming in and out of PC’s and networks acting much like an

administrator .

What Is a Virus? A virus is a software routine that is deliberately designed

to attach itself to another piece of software on a computer, perform some preprogrammed activity, and spread to other computers on the network.

The worst types of viruses are engineered to irretrievably destroy all or part of the data stored on the computer by wiping out hard drives.

Potentially damaging programs such as viruses, Trojan horses, and worms can find their way onto a network through file downloads, e-mails, or even removable disks.

Like biological viruses, computer viruses are designed to replicate themselves by infecting other pieces of software.

A virus on an infected removable disk can migrate to the computer’s hard drive and infect the code on the hard drive.

How Viruses Can Spread Throughout a Network

Virus Types

Boot sector viruses Executable file viruses Polymorphic viruses Stealth viruses Macro viruses Worms Trojan horses

Network Components

Mac AddressA MAC address (Media Access Control) also

referred to as a physical address is burned into each NIC card much like a serial number and no 2 cards are alike.

The first 3 sets of numbers identify the manufacturer while the last 3 sets identify

the ID number i.e. 00-05-1B-00-4B-F6

Network Protocols

Two of the basic protocols used today are:

TCP/IPand

NetBui

NetBEUI Characteristics

Original Microsoft Windows default networking protocol

Designed for small local area networks (LANs)

Does not support Internet communications

Does not need configuration

TCP Characteristics

TCP is the acronym for Transmission Control Protocol.

TCP is Connection oriented Reliable

It is used to carry large amounts of data. It provides services that Internet Protocol

(IP) lacks.

TCP/IP History

Developed in the 1970s Created for use on the ARPANET Used by UNIX Predates the PC, the Open Systems

Interconnection (OSI) model, and Ethernet

Platform and operating system independent

IP Address

Identifies the computer to the network

Required for TCP/IP communication Must be unique on the network Must not be chosen at random Must be assigned by a network

administrator

The Four TCP/IP Layers

Link. Includes Serial Line Internet Protocol (SLIP) and Point-to-Point Protocol (PPP)

Internet. Includes Internet Protocol (IP), Internet Control Message Protocol (ICMP), and Internet Group Membership Protocol (IGMP), plus some dynamic routing protocols

Transport. Includes Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

Application. Includes Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP)

The OSI Model and the TCP/IP Model

Basic TCP/IP Client Configuration Parameters

IP address Subnet mask Default gateway Domain Name System (DNS)

server address

Other TCP/IP Parameters

Parameter Function

Subnet mask Indicates which Internet Protocol (IP) address bits identify the network and which identify the hostRequired for TCP/IP communication

Default gateway

Identifies the router that the computer should use to access other networks

DNS server addresses

Identifies the DNS servers that the client will use to resolve host and domain names into IP addresses

The Local Area Connection Properties Dialog Box

IP Address Characteristics

32-bit value that contains a network identifier and a host identifier

Expressed in dotted decimal notation

Assigned to network interface adapters, not computers

IP Address Assignments

Every network interface adapter on a network must have The same network identifier as the others

on the network A unique host identifier

The Internet Assigned Numbers Authority (IANA) assigns network identifiers, but you typically obtain network addresses from an Internet service provider (ISP).

Network administrators assign host identifiers.

IP Address Classes

IP Address Class First Bit/Byte Values

Class First Bits First Byte Values

A 0 1–127

B 10 128–191

C 110 192–223

IP Addressing Rules

All the bits in the network identifier cannot be set to zeros.

All the bits in the network identifier cannot be set to ones.

All the bits in the host identifier cannot be set to zeros.

All the bits in the host identifier cannot be set to ones.

What Is a Subnet Mask?

A subnet mask is a 32-bit binary number that indicates which bits of an IP address identify the network and which bits identify the host.

The 1 bits are the network identifier bits and the 0 bits are the host identifier bits.

A subnet mask is typically expressed in dotted decimal notation.

Subnet Masks for IP Address Classes

Class Subnet Mask

A 255.0.0.0

B 255.255.0.0

C 255.255.255.0

Private Network Addresses

Class Network Addresses

A 10.0.0.0 through 10.255.255.255

B 172.16.0.0 through 172.31.255.255

C 192.168.0.0 through 192.168.255.255

IPv6 Addressing

Expands IP address space from 32 to 128 bits

Designed to prevent the depletion of IP addresses

Uses XX:XX:XX:XX:XX:XX:XX:XX notation

Telnet

Telnet provides remote control capabilities.

Telnet clients can execute commands on a server and view the results.

Telnet was designed for UNIX systems. All Windows versions include a Telnet

client.

FTP

You can use the File Transfer Protocol (FTP) to transfer files between computers, create and remove directories, rename and delete files, and manage access permissions.

All Windows computers have a command-line FTP client.

Windows 2000 and Windows NT servers have an FTP server built into Microsoft Internet Information Services (IIS).

UDP Characteristics

UDP is the acronym for User Datagram Protocol.

UDP is defined in RFC 768. It is a connectionless protocol. It is used primarily for brief

request/reply transactions.

DHCP

Dynamically allocates IP addresses from a pool

Reclaims unused addresses Prevents IP address duplication Supplies all TCP/IP parameters

The HOSTS File

A HOSTS file is a lookup table containing a list of host names and their equivalent IP addresses.

Each computer has its own HOSTS file. As the Internet grew, the HOSTS file

became impractical, and the Domain Name System (DNS) eventually replaced it.

DNS Characteristics

DNS defines A hierarchical namespace for

computer networks A service for resolving names into IP

addresses

The DNS Namespace

The DNS Name Resolution Process

Ping Characteristics

Supplied with virtually every TCP/IP implementation

Tests connectivity to another TCP/IP system

Syntax: ping target

Ping Output (Typical)

Pinging cz1 [192.168.2.10] with 32 bytes of data: 

Reply from 192.168.2.10: bytes=32 time<10ms TTL=128

Reply from 192.168.2.10: bytes=32 time<10ms TTL=128

Reply from 192.168.2.10: bytes=32 time<10ms TTL=128

Reply from 192.168.2.10: bytes=32 time<10ms TTL=128

Ping statistics for 192.168.2.10:Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:Minimum = 0ms, Maximum = 0ms, Average = 0ms

Types of Remote Network Connections

Computer to Internet service provider (ISP)

Computer to private network Computer to computer Network to network

Public Switched Telephone Network (PSTN) Technical name for the standard voice

telephone system Also known as the Plain Old Telephone

Service (POTS) Works with asynchronous modems to

transmit data between computers at almost any location

Typically uses copper-based, twisted-pair cable with RJ-11 jacks

Modems

A modem (modulator/demodulator) is required to convert a computer’s digital signals to the analog signals used by the PSTN.

At the other end of the connection, another modem converts the analog signals back to digital.

Modem Communications

Virtual Private Network (VPN) Communications

The remote user connects to the Internet by using a modem to dial in to a local ISP.

The network is permanently connected to the Internet and has a server that is configured to receive incoming VPN connections.

The remote computer and the network server establish a secured connection across the Internet. This technique is called tunneling, because

the connection runs across the Internet inside a secure conduit.

Integrated Services Digital Network

Integrated Services Digital Network (ISDN) is a high-speed digital dial-up service that uses the standard PSTN infrastructure.

It is used primarily for Internet connections, but it also supports special devices such as ISDN telephones and fax machines.

The Basic Rate Interface (BRI) provides two64-Kbps B channels and one 16-Kbps D channel.

The Primary Rate Interface (PRI) provides 23 64-Kbps B channels and one 64-Kbps D channel.

For computer connections, ISDN requires a Network Terminator 1 (NT-1) and a terminal adapter.

ISDN Connections

DSL Service Types Service Transmission Rate Link

Length Applications

High-bit-rate Digital Subscriber Line (HDSL)

1.544 Mbps full-duplex (using two wire pairs) or 2.048 Mbps full-duplex (using three wire pairs)

12,000 to 15,000 feet

Used by large networks as a substitute for T-1 leased line connections, LAN and private branch exchange (PBX) interconnections, or frame relay traffic aggregation

Symmetrical Digital Subscriber Line (SDSL)

1.544 Mbps full-duplex or 2.048 Mbps full-duplex (one wire pair)

10,000 feet

Same as HDSL

Asymmetrical Digital Subscriber Line (ADSL)

1.544 to 8.448 Mbps downstream; 16 Kbps to 640 Kbps upstream

10,000 to 18,000 feet

Internet/intranet access, remote LAN access, virtual private networking, video on demand, Voice over IP

ADSL Connections

CATV Networks Broadband networks owned by cable

television companies Provide Internet access through the

same cable used for television signals

Run at 512 Kbps or more Bandwidth shared with other users

in the area Provide Internet connections only

CATV Connections

Satellite Connections

Provide Internet access only Usually downstream only Require a dial-up connection for

upstream traffic

PPP

Stands for Point-to-Point Protocol Used for dial-up Internet connections and

other wide area network (WAN) technologies

What Is Fault Tolerance?

Depending on the organization, an equipment failure or other service interruption can mean lost productivity, lost revenue, and sometimes lost lives.

Fault-tolerance mechanisms enable a computer or a network to continue operating despite the failure of a major component.

When network functions are absolutely critical, the fault-tolerance mechanisms can be elaborate.

In most cases, however, fault-tolerance mechanisms protect only a few key components from outages due to hardware or software faults.

Mirroring

Mirroring is an arrangement in which two identical hard drives connected to a single host adapter always contain identical data. The two drives appear to users as one logical

drive. Whenever users save data to the mirror set,

the computer writes it to both drives simultaneously.

If one hard drive unit fails, the other takes over immediately until the malfunctioning drive is replaced.

RAID Redundant array of independent disks (RAID) is a

comprehensive data availability technology with various levels that provide all of the functions of mirroring, duplexing, volumes, and disk striping.

Although RAID is available as a software product that works with standard disk drives, many high-end servers use dedicated RAID drive arrays, which

Consist of multiple hard drive units in a single housing Often have hot swap capability

Hot swapping is the ability to remove and replace a malfunctioning drive without shutting off the other drives in the array, so the data is continuously available to network users during the drive repair.

RAID Levels

Level Technology Function

0 Disk striping Enhances performance by writing data to multiple disk drives, one block at a time; provides no fault tolerance.

1 Disk mirroring and duplexing

Provides fault tolerance by maintaining duplicate copies of all data on two drives. Disk mirroring uses two drives connected to the same host adapter, and disk duplexing uses two drives connected to different host adapters.

2 Hamming error-correcting code (ECC)

Ensures data integrity by writing error-correcting code to a separate disk drive; rarely implemented.

3 Parallel transfer with shared parity

Provides fault tolerance by striping data at the byte level across a minimum of two drives and storing parity information on a third drive. If one of the data drives fails, its data can be restored by using the parity information.

RAID Levels (Cont.)

Level Technology Function

4 Independent data disks with shared parity

Identical to RAID 3, except that the data is striped across the drives at the block level.

5 Independent data disks with distributed parity

Provides fault tolerance by striping both data and parity across three or more drives instead of using a dedicated parity drive, as in RAID 3 and RAID 4.

6 Independent disks with two-dimensional parity

Provides additional fault tolerance by striping data and two complete copies of the parity information across three or more drives.

7 Asynchronous RAID

Proprietary hardware solution that consists of a striped data array and a separate parity drive, plus a dedicated operating system that coordinates the disk storage activities.

NAS

Network attached storage (NAS) uses a dedicated storage appliance that connects directly to the network and contains its own embedded operating system.

NAS is essentially a multiplatform file server.

Computers on the network can access the NAS appliance in a variety of ways.

SANs A Storage Area Network (SAN) is a separate

network installed at a local area network (LAN) site that connects servers to disk arrays and other network storage devices.

SANs make it possible to use dedicated storage hardware arrays without overloading the client network with storage-related traffic.

SANs typically use the Fibre Channel protocol to communicate, but they can theoretically use any network medium and protocol.

Network Redundancy