A computer network is a group of computers linked to each other through a transmission medium that enables the computer to communicate with another computer and share their resources, data, and applications. There are mainly three types of computer networks based on their size: 1. Local Area Network (LAN) • A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. • LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users. • It is limited in size, typically spanning a few hundred meters, and no more than a mile. • It is fast, with speeds from 10 Mbps to 100 Mbps. • LAN’s can be either wired or wireless. Twisted pair, coax or fibre optic cable can be used in wired LAN’s. • Nodes in a LAN are linked together with a certain topology. These topologies include: Bus ,Ring & Star Fig: LAN 2. Metropolitan Area Network (MAN) • A metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus. • A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. • A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. • A MAN often acts as a high speed network to allow sharing of regional resources. • Examples of MAN: Telephone company network that provides a high speed DSL to customers and cable TV network.
Fig: MAN 3. Wide area network (WAN) • WAN covers a large geographic area such as country, continent or even whole of the world. • A WAN is two or more LANs connected together. The LANs can be many miles apart. • To cover great distances, WANs may transmit data over leased high-speed phone lines or wireless links such as satellites. • Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data. • The world's most popular WAN is the Internet. Fig: WAN
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