Computer Networks

Computer network connects two or more autonomous computers.

The computers can be geographically located anywhere.

Introduction to Computer Networks

LAN, MAN & WAN

Introduction to Computer Networks

Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)

Network in a City is call MAN (Metropolitan Area Network)

Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)

Applications of Networks

Introduction to Computer Networks

Resource SharingHardware (computing resources, disks, printers)Software (application software)

Information SharingEasy accessibility from anywhere (files, databases)Search Capability (WWW)

CommunicationEmailMessage broadcast

Remote computing

Distributed processing (GRID Computing)

LAN

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Local Area Networks (LANs)

Local Area Networks are privately-owned networks within a small area, usually a single building or campus of up to a few kilometers.

Since it is restricted in size, that means their data transmission time can be known in advance, and the network management would be easier.

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Cost reductions through sharing of information and databases, resources and network services.

Increased information exchange between different departments in an organization, or between individuals.

The trend to automate communication and manufacturing process.

Improve the community security.

Increasing number and variety of intelligent data terminals, PCs and workstations.

Motivations for Local Area NetworkingThe growing demand for local area networks is due to technical, economic and organizational factors:

Local Area Networks (LANS) …

LANS: Hardware Devices …

• Network Interface Cards (NICs)

• Repeaters

• Bridges

• Routers

• Switches

Network Topology

The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.

Introduction to Computer Networks

MAN

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Metropolitan area network

• A Metropolitan Area Network (MAN) is a network that is utilized across multiple buildings

• Commonly used in school campuses or large companies with multiple buildings

• Is larger than a LAN, but smaller than a WAN• Is also used to mean the interconnection of several

LANs by bridging them together. This sort of network is also referred to as a campus network

Metropolitan Area Networks (MANs)

• A Metropolitan Area Network is a system of LANs connected throughout a city or metropolitan area. MANs have the requirement of using telecommunication media such as voice channels or data channels.

• Branch offices are connected to head offices through MANs. Examples of organizations that use MANs are universities and colleges, grocery chains, and banks.

Metropolitan Area Networks (MANs)…

WAN

Wide Area Networks (WANS)

WANs connect LANs together between cities

Wide Area Networks (WANS) …

The main difference between a MAN

and a WAN is that the WAN uses Long

Distance Carriers. Otherwise the same

protocols and equipment are used as a

MAN.

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Wide area network

• A Wide Area Network is a network spanning a large geographical area of around several hundred miles to across the globe

• May be privately owned or leased• Also called “enterprise networks” if they are privately owned by

a large company• It can be leased through one or several carriers (ISPs-Internet

Service Providers) such as AT&T, Sprint, Cable and Wireless• Can be connected through cable, fiber or satellite • Is typically slower and less reliable than a LAN• Services include internet, frame relay, ATM (Asynchronous

Transfer Mode)

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Network Interconnection Components

• Networks can be connected to each other through several components– Repeater– Bridge– Router

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Repeater

• Regenerates and propagates all electrical transmissions between 2 or more LAN segments

• Allows extension of a network beyond physical length limitations• Layer 1 of the “OSI model”

HigherLayers

Physical

HigherLayers

PhysicalPhysicalRepeater

Network A Network B

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Bridge

• Connects 2 or more LAN segments and uses data link layer addresses (e.g.MAC addresses) to make data forwarding decisions

• Copies frames from one network to the other• Layer 2 of the “OSI model”

HigherLayers

Physical

HigherLayers

PhysicalPhysical 1

BridgeData Link

23-01-88-A8-77-45

Physical 2

Data Link Data Link Data Link

53-F1-A4-AB-67-4F

Node in Network A Node in Network B

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Router

• Connects 2 or more networks and uses network layer addresses (like IP address) to make data forwarding decisions

• Layer 3 of the “OSI model”

HigherLayers

Physical

HigherLayers

PhysicalPhysical 1

Router

Data Link

Physical 2

Data Link Data Link

A node in Network A A node in Network B

Data Link

Network145.65.23.102

Network137.22.144.6 Network Network