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Introduction to Computer Networks

Network and networking

A group of computers and other devices connected together is called network and the concept of connected computers sharing resources is called networking. The computers can be geographically located anywhere.

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

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

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

Applications of Networks:
Resource Sharing

(computing resources, disks,

-Software (application software)

Information Sharing

-Easy accessibility from anywhere (files,

-Search Capability (WWW)


-Message broadcast

Remote computing
Distributed processing (GRID Computing)
Preserving information
Protecting information

There are three roles for computers in LAN:

-Clients- which use but do not provide network resources
-Peers- which both use and provide network resources
-Server- which provide network resources

Based on the roles of the computers attached, networks are divided into three types:

-server-based/client-server: containing clients and the servers that support them
-Peer /peer-to-peer: which have no servers and use the network to share resources among
independent peers.
-Hybrid network: which is a client-server network that also has peers sharing resources.

Server-based: Sever based networks are defined by the presence of servers on the network that provide security and administration of the network. Server-based networks divide processing tasks between clients and servers. Clients
request services and servers deliver them. Server computers are more powerful than client computers.


-sentral security Central file storage
-Ability to share expensive equipment
-Optimized dedicated server
-Less intrusive security
-Free of users from the task of sharing
-Easy manageability of large number of users


-Expensive dedicated hardware
-Expensive network OS software and client
-A dedicated network administrator

Peer Networks: Peer networks are defined by a lack of central control over the network. Users simply share disk space and resources Peer networks are organized into workgroups. Workgroups have very little security control.


-No extra investment in server hardware or
software is required
-Easy setup
-No network administrator required
-Ability of users to control resources sharing
-No reliance on other computers for their
-Lower cost for small networks


-Additional load on computers because of
resource sharing
-Inability of peers to handle as many network connections as servers
-Lack of central organization
-No central point of storage
-Weak and intrusive security
-Lack of central management


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