A Metropolitan Area Network (MAN) is a network which connects various computers, resources and users in a geographical spread larger than a Local Area Network (LAN) but has a smaller area than a Wide Area Network (WAN). Thus, several LANs could be connected by the use of bridges and backbone lines. Here a backbone line is merely a transmission line that carries data gathered from smaller lines which are interconnected to it. As compared to a LAN, which may be limited to a building or a couple of buildings on campus, a MAN covers a large area from Five to Fifty Kilometre in diameter. Many of the MANs may cover almost an area of the size of a city or they may be limited to a group of buildings, of course depending on the need.
A MAN serves a role similar to an Internet Service Provider (ISP) but this may be for corporate users with large LANs. A MAN may not generally be owned by a single proprietor or organisation. A MANs communication links, its equipment, its various services may be owned by a group of users or by a single service provider who may sell the service to the users. Thus, each user in a MAN can negotiate the level of service provided to him/her.
A MAN can be a private or public network. An example of a private MAN can be a large department which is spread over several buildings. Also, an example of a public MAN is the infrastructure which a telecommunication operator installs in a city in order to provide internet services to its customers situated in the part of a city.
Advantages of using a MAN
- It offers centralised management of data enabling us to connect many fast LANs
- With the use of optical fibres nowadays, MANs have become faster and efficient.
- Saves cost when it comes to handing data as compared with a
To understand MAN better, let us briefly understand LANs first.
A LAN is a communication network which connects computers in a local setup i.e. within a building or a group of buildings. LANs usually are under a single administrative authority. Most of the resource and data sharing in a LAN is assumed to be shared with trusted users.
The use of physical means such as cables, optical fibres, Ethernet card etc usually makes LANs very high speed. A LAN connects to other LANs through a router and also to the larger MAN via such Routers. Various communication protocols are followed in establishing such connections.
(A diagram representing MAN in the network hierarchy. Various LANs are connected to a MAN as can be seen in this diagram. Then the MAN is within the scheme of a larger WAN. )
How does a MAN work?
A MAN is generally used to connect LANs which are geographically dispersed. Thus, its main goal is to establish a communication link between two independent LAN nodes. A Metropolitan Area Network (MAN) usually uses Optical Fibre to be established. It can also be established via copper and wireless technologies, depending upon the network requirements such as speed, latency and budget.
A MAN network is established using switches and routers. A router is a network device which helps data packets to reach their appropriate node by the use of information stored in their headers and address according to some network protocol.
A bridge simply connects two different LANs and a multiple-port bridge is known as a switch. It (the switch) is selective in forwarding information packet to only the required machine or node. Simply speaking, a switch keeps an eye on the data transfer.
Technologies needed to develop a MAN
The various technologies needed to implement a Metropolitan Area Network (MAN) are FDDI (Fibre Distributed Data Interface), ATM (Asynchronous Transfer Mode) and SMDS (Switched Multi Megabit Data Service).
Most popular among these technologies is the ATM. In ATM data is transmitted in the form of small identical fixed-size packets called as cells. Thus data is transferred over time in a reliable and uniform fashion. Uniform packet size (in ATM mode) ensures efficiency and effective bandwidth usage.
FDDI technology is standard for data transfer over a LAN. Its range may be extended to 200 kilometres, thus supporting many a thousand of users. It uses optical fibre as its basic infrastructure and hence the name FDDI. And this may be the reason that FDDI is referred to as MAN or WAN technology.
SMDS is a 1990s technology which is used to connect LAN, MAN or WAN to exchange data. It is a connectionless technology which means data is transferred by storing it into a header, which then reaches its destination in an independent way through a network.
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