1.4 Computer networks

History of computer networks

Computer network

Computer network is composed of multiple connected computers that communicate over a wired or wireless medium to share data and other resources.

Network data protocols are used to communicate on the network between computers.

The size and scalability of any computer network are determined both by the physical medium of communication and by the software controlling the communication (i.e., the protocols).

The field of computer networking and today's Internet trace their beginnings back to the early 1960s, a time at which the telephone network was the world's dominant communication network. The global Internet's origin was the Advanced Research Projects Agency Network (ARPANET) of the U.S. Department of Defense in 1969 Nowadays, computer networks are developed rapidly

Classification of computer networks

Networks can be categorized in several different ways, for example,

• By network layer
• By scale
• By connection method
• By functional relationship
• By network topology
• By protocol

Classification by scale

A Local Area Network (LAN) is a group of computers and associated devices that share a common communications line and typically share the resources of a single processor or server within a small geographic area

A Wide Area Network (WAN) is a computer network that spans a relatively large geographical area (diameter of about 200 km)

GAN (Global Area Network) A network spanning a between geographically distinct cities

Classification by functional relationship

Server based (client/server): Computers set up to be primary providers of services such as file service or mail service.

The computers providing the service are called servers

The computers that request and use the service are called client computers.

Peer-to-peer

Various computers on the network can act both as clients and servers.

Example Many Microsoft Windows based computers allow file and print sharing.

Many networks are combination peer-to-peer and server based networks.

Major components of a computer network

A computer network possibly includes :

• Computers: critical elements of any computer network. They can be considered nodes
• A network card, NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network.
• Network media (sometimes referred to as networked media) refers to media mainly used in computer networks : cable, telephone line or wireless.
• Network connection equipments : HUB, SWITCH, ROUTER,etc.
• Network Operating System (NOS) is an operating system that includes special functions for connecting computers and devices into a local-area network (LAN) or Inter-networking. Some popular NOSs for DOS and Windows systems include Novell NetWare, Windows NT and 2000, Sun Solaris and IBM OS/2.
• Network software.
• Network services, for example email.

Network topology

Network topology is the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes .