Senin, 15 Oktober 2012

Metropolitan area network


metropolitan area network (MAN) is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks (or WAN) and the Internet.
The IEEE 802-2002 standard describes a MAN as being:[1]
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.
Authors Kenneth C. Laudon and Jane P. Laudon (2001) of Management Information Systems: Managing the Digital Firm 10th ed. define a metropolitan area network as:
A Metropolitan Area Network (MAN) is a large computer network that spans a metropolitan area or campus. Its geographic scope falls between a WAN and LAN. MANs provide Internet connectivity for LANs in a metropolitan region, and connect them to wider area networks like the Internet.
It can also be used in cable television.

[edit]Implementation

Some technologies used for this purpose are Asynchronous Transfer Mode (ATM), FDDI, and SMDS. These technologies are in the process of being displaced by Ethernet-based connections (e.g., Metro Ethernet) in most areas. MAN links between local area networks have been built without cables using either microwaveradio, or infra-red laser links. Most companies rent or lease circuits from common carriers because laying long stretches of cable can be expensive.
DQDBDistributed-queue dual-bus, is the metropolitan area network standard for data communication. It is specified in the IEEE 802.6standard. Using DQDB, networks can be up to 20 miles (30 km) long and operate at speeds of 34 to 155 Mbit/s.
Several notable networks started as MANs, such as the Internet peering points MAE-WestMAE-East, and the Sohonet media network.[citation needed]

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