COMPUTER NETWORKS

A computer network is a set of devices which communicate and share resources. These devices are mostly computers, and sometimes stand-alone hard disk, telephones, printers and terminals (processorless computers which must rely on other computers to work)

Server and Client

A computer network interaction is based on the client server architecture. When considering a single interaction, one computer is the server and the other one is the client. The server is the computer which is offering its resources, usually programmed to wait until someone asks for its resource. The client is the computer which uses the resource, which sends the request to waiting server.

E.g. when sending a document to the printer, the user’s computer is the client while the printer is the server; when retrieving personal emails, the user’s computer is the client which connects to the mail server asking for available emails. When   talking to a friend on an internet chat, the interaction is composed of two difference interactions: the user’s computer as a client is connected to the chat room’s computer acting as a server, and the friend’s computer does the same interaction.

The same computer may be the client for a service and the server for another service. For example, a library computer may have a CD inside its reader shared to the network (server for the CD) and may be at the same time by a user to print his own documents (client for the printer)

Area: Computer networks are commonly divided into three categories:

·        Local Area Network (LAN or Intranet), a LAN is a system wherebyindividual PCs are connected together within acompany or organization

·        Wide Area Network (WAN or Internet) as the name impliesallows you to connect to other computers over awider area (i.e. the whole world).

·        Virtual Private Network (VPN) is a way to recognize a computer, even though connected via internet, will be considered as part of the LAN, for as long as it remains connected. VPN is typically required to identify portable computers connected via wireless connection.

Uses of Network

If ten people are working together within an office it makes sense for them all to be connected.

• In this way the office can have a single printer and all ten people can print to it.

• In a similar way other devices such as modems or scanners can be shared.

• Even more useful is the ability to share information when connected to a network.