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Thursday, July 9, 2009

Quick Tech Tip : Metropolitan Area Networks - MANs

A metropolitan area network, or MAN is basically a bigger version of LAN. MAN is a computer networks usually spanning a campus or a city, which typically connect a few local area networks using high speed backbone technologies. A MAN supports both data and voice. A MAN just has one or two cables and does not contain switching elements.
A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. MANs can also depend on communications channels of moderate-to-high data rates. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. MANs might also be owned and operated as public utilities. They will often provide means for internetworking of local networks. Metropolitan area networks can span up to 50km, with the devices being used such as modem and wire/cable devices.
The standard that has been adopted for MANs is called DQDB (Distributed Queue Dual Bus). DQDB consists of two unidirectional cables or buses to which all other computers are connected. Each bus has a head-end which initiates transmission activity.
There are three important features which discriminate MANs from LANs or WANs:
1. The network size falls intermediate between LANs and WANs. A MAN typically covers an area of between 5 and 50 km range. Many MANs cover an area the size of a city, although in some cases MANs may be as small as a group of buildings.
2. A MAN, its communications links and equipment are generally owned by either a consortium of users or by a network service provider who sells the service to the users.
3. A MAN often acts as a high speed network to allow sharing of regional resources. It is also frequently used to provide a shared connection to other networks using a link to a WAN.

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