v  The Local Area Network (LAN) is a network that is usually contained within a room, floor, or building.

v  A local area network is usually privately owned and links the devices in a single office, building or campus of up to a few kilometers in size. Depending on the needs of an organization and the type of technology used, a LAN can be as simple as two PCs and printer in someone’s whole office or it can extend throughout a company and include voice, sound, and video peripherals.

v  A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Rarely are LAN computers more than a mile apart.

 

v Characteristics of LAN

       The defining characteristics of LANs, in contrast to Wide Area Networks (WANs), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.

       Initially, LANs were limited to a range of 185 meters or 600 feet and could not include more than 30 computers.

       Today, a LAN could connect a max of 1024 computers at a max distance of 900 meters or 2700 feet.

       LANs are designed to allow resources to be shared between personal computers or workstations. The resources to be shared can include hardware (e.g. a printer), software (e.g. an application program), or data.

       A common example of LAN, found in many business environments, links a work group of task-related computes, for example, engineering workstations or accounting PCs.

       One of the computers may be given a large capacity disk drive and become a server to the other clients. Software can be stored on this central server and used as needed by the whole group. In this example, the size of the LAN may be determined by licensing restriction on the number of users per copy of software, or by restrictions on the number of users licensed to access the operating system.

       In addition to size, LANs are distinguished form other types of networks by their transmission media and topology. In general, a given LAN will use only one type of transmission medium. The most common LAN topologies are bus, ring, and star. Traditionally, LANs have data rates in the 4 to 16 Mbps range. Today, however, speeds are increasing and can reach 100 Mbps.

       In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network. Computers connected to the file server are called workstations. The workstations can be less powerful than the file server, and they may have additional software on their hard drives.

       On most LANs, cables are used to connect the network interface cards in each computer.

       Ethernetover unshielded twisted pair cabling, and Wi-Fi are the two most common technologies currently, but ARCNET, Token Ring and many others have been used in the past.

v  A MAN is a Metropolitan Area Network, which is an intermediate step between LAN and WAN. Typically, a WAN is kept to one geographic region. A campus network that connects multiple buildings in a given area is an example of a MAN.

v  A metropolitan area network is designed to extend over an entire city. It may be a single network such as a cable television network, or it may be a means of connecting a number of LANs into a larger network so that resources may be shared LAN-to-LAN as well as device-to-device.

v  Metropolitan area networks, or MANs, are large computer networks usually spanning a city. They typically use wireless infrastructure or Optical fiberconnections to link their sites.

v  A Metropolitan Area Network (MAN) covers larger geographic areas, such as cities or school districts. By interconnecting smaller networks within a large geographic area, information is easily disseminated throughout the network. Local libraries and government agencies often use a MAN to connect to citizens and private industries.

v  A MAN may be wholly owned and operated by a private company, or it may be a service provided by a public company, such as a local telephone company. Many telephone companies provide a popular MAN service called Switched Multi-megabit Data Services (SMDS).

 

v  A MAN is optimized for a larger geographical area than is a LAN, ranging from several blocks of buildings to entire cities.

v  MANs can also depend on communications channels of moderate-to-high data rates.

v  A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations.

v  MANs might also be owned and operated as public utilities. They will often provide means for internetworking of local networks.

v  Metropolitan area networks can span up to 50km, devices used are modem and wire/cable

 

v  Implementation of MAN

       Some technologies used for this purpose are ATM, FDDI, and SMDS. These older technologies are in the process of being displaced by Ethernet-based MANs (e.g. Metro Ethernet) in most areas.

       MAN links between LANs have been built without cables using either microwave, radio, or infra-red laser links.

       DQDB, Distributed 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 30 miles long and operate at speeds of 34 to 155 Mbit/s.

       Several notable networks started as MANs, such as the Internet peering points MAE-West, MAE-East, and the Sohonetmedia network.[citation needed]

 

 

v  A Wide Area Network (WAN) connects different LANs over great distances. The connection between LANs is usually a dial-up connection (shown in the next section) or a leased line from a national telephone carrier.

v  A wide are network provides long-distance transmission of data, voice, image, and video information over a large geographical area that may comprises a country, a continent or even the whole world.

v  Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries).

v  Or, less formally, a network that uses routers and public communications links.

v  In contrast to LAN (which depends on their own hardware for transmission), WANs may utilize public, leased, or private communication devices, usually in communication and can therefore span an unlimited number of miles.

v  A WAN that is wholly owned and used by a single company is often referred to as an enterprise network.

v  The largest and most well-known example of a WAN is the Internet.

v  Characteristics of WAN

             Covers a long distance [more than 1 kilometer (> 1 km)]

             Usually spans several locations (even world wide)

             Usually has a larger number of users (100’s or even 1000’s)

             Implemented as a client-server model

v  WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations.

v  Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization’s LAN to the Internet.

v  WANs are often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. Leased lines can be very expensive.

v  Instead of using leased lines, WANs can also be built using less costly circuit switching or packet switching methods.

v  Network protocols including TCP/IPdeliver transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relayare often used by service providers to deliver the links that are used in WANs. X.25 was an important early WAN protocol, and is often considered to be the “grandfather” of Frame Relay as many of the underlying protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.

v  Performance improvements are sometimes delivered via WAFS or WAN Optimization.