Computer Networks - An Overview
Definition and overview of Local Area Network (LAN) and Wide Area Network (WAN)
A Network, in IT-related parlance, consists of two or more computing devices linked together in order to share data. Networks are built using a combination of computer hardware and software. The most simple network simply connects two computers (or other computing devices such as printers or scanners) through a cable or wire. A LAN, or Local Area Network, is a set of connected computers and peripherals like printers or scanners that are located in a small area like a school or office building. Computers on a LAN may share files and printers and a connection to the outside - to other LANs and the Internet. A Wide Area Network (WAN) connects LANs or individual computers located in diverse locations, perhaps across metropolises or continents. While LANs use equipment like ethernet cables that may be acquired commercially, WANs are built by large telecommunications companies such as AT&T with special equipment. The Internet is a WAN that connects LANs and other wide area networks across the globe. Wireless networks utilize radio waves and/or microwaves to create channels of communication. Wireless networking is a more modern alternative to regular networks that rely on copper or fiber optic cabling between devices.
Fig 1a: A Local Area Network
Most home computers are connected to the Internet through twisted pair 'Ethernet' cables that are in turn connected to the Internet Service Provider - usually a telephone company - through the telephone or TV cable line. Larger institutions with sizeable LANs have a rack that contains wiring connections and equipment; certain types of cables connect such racks to other LANs and the Internet. High-speed fibre optic cable is used to send Internet traffic across long distances; twisted pair and coaxial cables are sometimes used for remote areas.
Fig 1b: A Wide Area Network
Networks may be designed according to the Client-server model or the peer-to-peer model. The Client-server model features a central 'server' which is a computer or set of computers that store e-mail, Web pages, files and applications. They receive requests for different resources from the client computers and service these requests in a set order. In a peer-to-peer network, all computers are configured to perform the same functions and contain the same software.
