A metropolitan area network (MAN) is a medium-size computer network. A MAN is larger than LAN, but smaller than WAN. MAN is usually characteried by very high-speed connections using a high-capacity backbone network technology (eg. optical fibers or other digital media) as well as providing up-link services to WANs (or WAN) and the Internet. MAN links between LANs have been built with wireless links using either microwave, radio, or infra-red laser transmission.
Distributed Queue Dual Bus (DQDB) is the MAN standard specified by the Institute Of Electrical And Electronics Engineers (IEEE) as IEEE 802.6. Using this standard, a MAN extends up to 30-40 km, or 20-25 miles.
Three important features of MANs are used to discriminate MANs from LANs or WANs:
The network size of MANs are between LANs and WANs. A MAN typically covers an area of between 5 and 50 km diameter. Generally, MANs cover an area the size of a city. But in some cases MANs may be as small as a group of buildings (similar to LANs) or as large as a part of a city.
A MAN is not generally owned by a single organisation but usually used by many individuals and organizations. They sell the service to the users. This level of service provided to each user must therefore be negotiated with the MAN operator, and some performance guarantees are normally specified.
A MAN often acts as a high speed network to allow sharing of regional resources (similar to a large LAN). It is also frequently used to provide a shared connection to other networks using a link to a WAN.
With the development of Internet services and a variety of value-added services, MANs will require more wider bandwidth and higher speed. Nowadays MANs have been in a “bottleneck” of business development. In addition, several types of operations on integrated access and management of MANs also make higher technology requirements. As a result, MANs must be continued developing in some time to come to satisfy those requirements.