LAN,MAN and WAN

Local Area Network(LAN)

It is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media.
ARCNET, Token Ring and other technology standards have been used in the past, but Ethernet over twisted pair cabling, and Wi-Fi are the two most common technologies currently used to build LANs.

LAN is generally limited to specific geographical area less than 2 K.M., supporting high speed networks. A wide variety of LANs have been built and installed, but a few types have more recently become dominant. The most widely used LAN system is the Ethernet system based on the bus topology.
Intermediate nodes (i.e., repeaters, bridges and switches) allow to be connected together to from larger LANs. A LAN may also be connected to another LAN or to WANs and MANs using a “router” device.

There are essentially five components of a LAN:
1) Network devices such as Workstations, printers, file servers which are
normally accessed by all other computers.
2) Network Communication Devices i.e., devices such as hubs, routers, switches etc. used for network connectivity.
3) Network Interface Cards (NICs) for each network device required to access the network. It is the interface between the machine and the physical network.
4) Cable as a physical transmission medium.
5) Network Operating System –software applications required to control the use of network operation and administration.

Characteristics of LAN
· It connects computers in a single building, block or campus, i.e. they work in a restricted geographical area.
· LAN’s are private networks, not subject to tariffs or other regulatory controls.
· LAN’s operate at relatively high speed when compared to the typical WAN
(.2 to 100 MB /sec).
· There are different types of Media Access Control methods in a LAN, the
prominent ones are Ethernet, Token ring.
· The networking is done through Buses or Rings.

ADVANTAGES OF LAN
· It allows sharing of expensive resources such as Laser printers, software and mass storage devices among a number of computers.
· LAN allows for high speed exchange of essential information.
· It contributes to increased productivity. A LAN installation should be studied closely in the context of its proposed contribution to the long range interest of the organization.

DISADVANTAGES OF LAN

· The financial cost of LAN is still high in comparison with many other
alternatives.
· It requires memory space in each of the computers used on the network. This reduces the memory space available for the user’s programs.
· Some type of security system must be implemented if it is important to
protect confidential data.
· Some control on the part of the user is lost. You may have to share a printer with other users. You may face a situation like, for example, the entire network suddenly locking up because one user has made a mistake.

Metropolitan Area Network(MAN)

A metropolitan area network (MAN) is a computer network that used to connect a city or a large campus. A MAN is usually interconnection of many 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:

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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.

Metropolitan Area Network 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.

1) The network size falls intermediate between LAN and WAN. A MAN typically covers an area of between 5 and 50 km diameter. Many MANs cover an area the size of a city, although in some cases MANs may be as small as a group of buildings or as large as the North of Scotland.
2) 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.

Characteristics of MAN
1) It generally covers towns and cities (50 kms)
2) It is developed in 1980s.
3) Communication medium used for MAN are optical fibers, cables etc.
4) Data rates adequate for distributed computing applications.

Wide Area Network(WAN)

A Wide Area Network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, or national boundaries) using private or public network transports. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable.




Characteristics of WAN
1) It generally covers large distances (states, countries, continents).
2) Communication medium used are satellite, public telephone networks which are connected by routers.
3) Routers forward packets from one to another (Table 1) a route from the sender to the receiver.