ENG224 INFORMATION TECHNOLOGY – Part II 5. Introduction to Networking 1 BY S K SATAPATHY

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INFORMATION TECHNOLOGY – Part II5. Introduction to Networking

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5. 5. Introduction to NetworkingIntroduction to Networking

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What is a Network?

A network consists of 2 or more computers connected together, and they can communicate and share resources (e.g. information)

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Why Networking?

• Sharing information — i.e. data communication

• Do you prefer these?

• Or this?

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devices that are connected in various ways in order to communicate and share resources

Usually, the connections between computers in a network are made using physical wires or cablComputer network A collection of computing es

However, some connections are wireless, using radio waves or infrared signals

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• Sharing hardware or software

• Centralize administration and support

• E.g. print document

• E.g. Internet-based, so everyone can access the same administrative or support application from their PCs

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FEATURES1.SPEED2.SHARE DATA/INFORMATION3.CENTRALISED DATA STORAGE.(BACKUP)4.SECURITY5. PRINT SERVICES(NETWORK PRINTER)6.FLEXIBLE ACCESS7.COST

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How many kinds of Networks?• Depending on one’s perspective, we can classify

networks in different ways

• Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless

• Based on network size: LAN and WAN (and MAN)

• Based on management method: Peer-to-peer and Client/Server

• Based on topology (connectivity): Bus, Star, Ring …

:

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• Two main categories:– Guided ― wires, cables– Unguided ― wireless transmission, e.g. radio,

microwave, infrared, sound, sonar

• We will concentrate on guided media here:– Twisted-Pair cables:

Unshielded Twisted-Pair (UTP) cables Shielded Twisted-Pair (STP) cables

– Coaxial cables– Fiber-optic cables

Transmission Media

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• If the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors

Twisted-Pair Cables

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Unshielded Twisted-Pair (UTP)

• Typically wrapped inside a plastic cover (for mechanical protection)

• A sample UTP cable with 5 unshielded twisted pairs of wires

MetalInsulator

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Shielded Twisted-Pair (STP)• STP cables are similar to UTP cables, except there

is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires

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Categories of UTP CablesEIA classifies UTP cables according to the quality:• Category 1 ― the lowest quality, only good for voice,

mainly found in very old buildings, not recommended now• Category 2 ― good for voice and low data rates (up to

4Mbps for low-speed token ring networks)• Category 3 ― at least 3 twists per foot, for up to 10 Mbps

(common in phone networks in residential buildings)• Category 4 ― up to 16 Mbps (mainly for token rings)• Category 5 (or 5e) ― up to 100 Mbps (common for

networks targeted for high-speed data communications)• Category 6 ― more twists than Cat 5, up to 1 Gbps

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Local-area network (LAN) A network that connects a relatively small number of machines in a relatively close geographical area

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LAN and WAN• Local Area Network (LAN)

• Small network, short distance

• A room, a floor, a building

• Limited by no. of computers and distance covered

• Usually one kind of technology throughout the LAN

• Serve a department within an organization

• Examples:

• Network inside the Student Computer Room

• Network inside Building

• Network inside your homeBY S K SATAPATHY

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• Wide Area Network (WAN)• A network that uses long-range telecommunication links

to connect 2 or more LANs(diff network)/computers housed in different places far apart.

• Towns, states, countries• Examples:

• Network of our Campus• Internet

WAN

Student Computer Centre

Your home

USA

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• Example of WAN: Broadband Cable Network

• Cable TV services have been extensively developed in most modern cities

• Cable TV companies try to make use of their coaxial cable installed (that are supposed to carry TV signals) to deliver broadband data services

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Wide-area network (WAN) A network that connects two or more local-area networks over a potentially large geographic distance

Often one particular node on a LAN is set up to serve as a gateway to handle all communication going between that LAN and other networks

Communication between networks is called internetworking

The Internet, as we know it today, is essentially the ultimate wide-area network, spanning the entire globe

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Metropolitan-area network (MAN) The communication infrastructures that have been developed in and around large cities

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LAN : 1. LAN stands for Local Area Network. 2. Used Guided Media 3. A communication network linking a number of stations in same local area. 4. LAN generally provides a high-speed 100 Kbps to 100 Mbps. MAN: 1. MAN stands for Metropolitan Area Network. 2. Use may be Guided or may be Unguided media. 3. This network shares the characteristics of packet broadcasting networks. 4. A MAN is optimized for a large geographical area than LAN. WAN : 1. WAN stands for Wide Area Network. 2. Used Unguided media. 3. A communication network distinguished from a Local Area Network. 4. Its long distance communications, which may or may not be provided by public packet network.

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LAN MAN WAN

1. LAN stands for Local Area Network. 2. Used Guided Media 3. A communication network linking a number of stations in same local area. 4. LAN generally provides a high-speed 100 Kbps to 100 Mbps.

1. MAN stands for Metropolitan Area Network. 2. Use may be Guided or may be Unguided media. 3. This network shares the characteristics of packet broadcasting networks. 4. A MAN is optimized for a large geographical area than LAN.

1. WAN stands for Wide Area Network. 2. Used Unguided media. 3. A communication network distinguished from a Local Area Network. 4. Its long distance communications, which may or may not be provided by public packet network.

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Figure 15.1 Local-area networks connected across a distance to create a wide-area network

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Peer-to-Peer Networks• Peer-to-peer network is also called workgroup• No hierarchy among computers all are equal• No administrator responsible for the network

Peer-to-peer

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• Advantages of peer-to-peer networks:• Low cost• Simple to configure• User has full accessibility of the computer

• Disadvantages of peer-to-peer networks:• May have duplication in resources• Difficult to impliment security policy• Difficult to handle uneven loading(

uneven load balancing even after several practice runs• Where peer-to-peer network is appropriate:

• 10 or less users• No specialized services required• Security is not an issue• Only limited growth in the foreseeable future

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Clients and Servers• Network ClientsClients (WorkstationWorkstation)

• Computers that request network resources or services

• Network ServersServers• Computers that manage and provide network resources

and services to clients

• Usually have more processing power, memory and hard disk space than clients

• Run Network Operating System that can manage not only data, but also users, groups, security, and applications on the network

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• Advantages of client/server networks• Facilitate resource sharing – centrally administrate and

control• Facilitate system backup and improve fault tolerance• Enhance security – only administrator can have access

to Server• Support more users – difficult to achieve with peer-to-

peer networks

• Disadvantages of client/server networks• High cost for Servers• Need expert to configure the network• Introduce a single point of failure to the system

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Documents

ENG224 INFORMATION TECHNOLOGY – Part II 5. Introduction to Networking 1 BY S K SATAPATHY