Chapter 2

This Chapter Covers…

• History of networking– Network devices– Cabling– Physical and logical layouts– LANs, MANs, WANs, SAN, VPN

• Bandwidth• Layered model

– OSI– TCP/IP– Differences and similarities between the two models

Evolution of Networking

• Business Applications

• Sneaker Net

• LAN

• WAN

History of Networking

• In 1947 the invention of a semiconductor transistor opened up many possibilities for making smaller, more reliable computers.

• In the late 1950s the integrated circuit that combined several, then many, and now millions, of transistors on one small piece of semiconductor was invented.

• Through the 1960s mainframes with terminals were commonplace, and integrated circuits were widely used.

• In 1977 the Apple Computer Company introduced the microcomputer, also known as the personal computer.

• In 1981 IBM introduced its first personal computer. The user-friendly Mac, the open-architecture IBM PC, and the further micro-miniaturization of integrated circuits led to widespread use of personal computers in homes and businesses.

• In the mid-1980s users with stand-alone computers started to share files using modems to connect to other computers.

• Starting in the 1960s and continuing through the 70s, 80s, and 90s, the Department of Defense (DoD) developed large, reliable, wide-area networks (WANs) for military and scientific reasons.

Networking Devices

• End-user devices • Network devices

– NIC – PCMCIA card – Repeaters– Hubs– Bridges– Switches– Routers

Networking Topology

• Network topology defines the structure of the network

• Physical topology– The actual layout of the wire or media.

• Logical topology– Defines how the media is accessed by the ho

sts for sending data

Physical Topology• A bus topology uses a single backbone cable that is terminated at b

oth ends. All the hosts connect directly to this backbone • A ring topology connects one host to the next and the last host to th

e first. This creates a physical ring of cable • A star topology connects all cables to a central point of concentratio

n • An extended star topology links individual stars together by connecti

ng the hubs and/or switches • A hierarchical topology is similar to an extended star. However, inst

ead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology

• A mesh topology is implemented to provide as much protection as possible from interruption of service. The use of a mesh topology in the networked control systems of a nuclear power plant would be an excellent example

Logical Topology• Broadcast topology

– Each host sends its data to all other hosts on the network medium

– There is no order that the stations must follow to use the network– It is first come, first serve– Ethernet works this way

• Token passing– Controls network access by passing an electronic token sequent

ially to each host– When a host receives the token, that host can send data on the

network. If the host has no data to send, it passes the token to the next host and the process repeats itself

– Two examples of networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI)

– A variation of Token Ring and FDDI is Arcnet• Arcnet is token passing on a bus topology.

Network Protocols

• Protocol suites are collections of protocols that enable network communication from one host through the network to another host

• A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate

• Protocols determine the format, timing, sequencing, and error control in data communication

• Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the original format

Protocols Control…

• How the physical network is built

• How computers connect to the network

• How the data is formatted for transmission

• How that data is sent

• How to deal with errors

Related organizations and committees

• Tthe Institute of Electrical and Electronic Engineers (IEEE)

• American National Standards Institute (ANSI)• Telecommunications Industry Association (TIA)• Electronic Industries Alliance (EIA)• The International Telecommunications Union (IT

U)– Formerly known as the Comité Consultatif Internation

al Téléphonique et Télégraphique (CCITT).

LAN Components

• Computers

• Network interface cards

• Peripheral devices

• Networking media

• Network devices

LAN technologies

• Ethernet

• Token Ring

• FDDI

Wide-area Networks

• WANs connect user networks over a large geographical area

• Allows computers, printers, and other devices on a LAN to share and be shared with distant locations

• Provide instant communications across large geographic areas

• Wide-area networking has also created a new class of workers called telecommuters, people who never have to leave their homes to go to work

WANs Are Designed To Do…

• Operate over a large geographically separated areas

• Allow users to have real-time communication capabilities with other users

• Provide full-time remote resources connected to local services

• Provide e-mail, World Wide Web, file transfer, and e-commerce services

WAN Technologies

• Modems

• Integrated Services Digital Network (ISDN)

• Digital Subscriber Line (DSL)

• Frame Relay

• US (T) and Europe (E) Carrier Series – T1, E1, T3, E3

• Synchronous Optical Network (SONET)

Metropolitan-area Networks

• A MAN is a network that spans a metropolitan area such as a city or suburban area

• A MAN usually consists of two or more LANs in a common geographic area

• Example– a bank with multiple branches may utilize a MAN

• Typically, a service provider is used to connect two or more LAN sites using private communication lines or optical services

• A MAN can also be created using wireless bridge technology by beaming signals across public areas.

Storage-Area Networks (SANs)

• SAN is a dedicated, high-performance network used to move data between servers and storage resources– Because it is a separate, dedicated network, it avoids

any traffic conflict between clients and servers

• SAN technology allows high-speed server-to-storage, storage-to-storage, or server-to-server connectivity – This method uses a separate network infrastructure th

at relieves any problems associated with existing network connectivity

SANs Features

• Performance – SANs enable concurrent access of disk or tape arrays

by two or more servers at high speeds, providing enhanced system performance

• Availability – SANs have disaster tolerance built in, because data c

an be mirrored using a SAN up to 10 kilometers (km) or 6.2 miles away

• Scalability – Like a LAN/WAN, it can use a variety of technologies.

This allows easy relocation of backup data, operations, file migration, and data replication between systems

Virtual Private Network (VPN)

• A VPN is a private network that is constructed within a public network infrastructure such as the global Internet

• Using VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquarters

Benefits of VPNs

• A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet

• VPNs maintain the same security and management policies as a private network

• They are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise customer's network.

Types of VPN

• Access VPNs – Provide remote access to a mobile worker and small office/home

office (SOHO) to the headquarters of the Intranet or Extranet over a shared infrastructure

– Access VPNs use analog, dialup, ISDN, digital subscriber line (DSL), mobile IP, and cable technologies to securely connect mobile users, telecommuters, and branch offices

• Intranet VPNs– VPNs link regional and remote offices to the headquarters of the

internal network over a shared infrastructure using dedicated connections

– Intranet VPNs differ from Extranet VPNs in that they allow access only to the employees of the enterprise

• Extranet VPNs – Extranet VPNs link business partners to the headquarters of the

network over a shared infrastructure using dedicated connections

– Extranet VPNs differ from Intranet VPNs in that they allow access to users outside the enterprise.

Intranets and Extranets

• Intranets– Intranets are designed to permit access by users who

have access privileges to the internal LAN of the organization

– Browser technology is used

• Extranets– Extranets refer to applications and services that are

Intranet based, and use extended, secure access to external users or enterprises

– This access is usually accomplished through passwords, user IDs, and other application-level security