Introduction to Computer Networks(Part 1)

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

• Hardware (computing resources, disks, printers)
• Software (application software)                

   Information Sharing

• Easy accessibility from anywhere (files, databases)
• Search Capability (WWW)

   Communication

• Email
• 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.

Advantages:

• strong central 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

Disadvantages:

•  Expensive dedicated hardware
• Expensive network OS software and client licenses
•  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.

Advantages:

• 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 operation
• Lower cost for small networks

Disadvantages:

• 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