Local area network

LAN redirects here, for other uses see LAN (disambiguation).

A local area network (LAN) is a computer network covering a small local area, like a home, office, or small group of buildings such as a college. Current LANs are most likely to be based on switched Ethernet or Wi-Fi technology running at from 10 to 10000 Mbit/s. The defining characteristics of LANs in contrast to WANs are: a) much higher data rates, b) smaller geographic range and c) they do not involve leased telecommunication lines.

Technical aspects

Although switched Ethernet is now most common at the physical layer, and TCP/IP as a protocol, historically many different options have been used (see below) and some continue to be popular in niche areas. Larger LANs will have redundant links, and routers or switches capable of using spanning tree protocol and similar techniques to recover from failed links. LANs will have connections to other LANs via routers and leased lines to create a WAN. Most will also have connections to the large public network known as the Internet, and links to other LANs can be 'tunnelled' across this using VPN technologies.

Local Area Network, in computer science, collection of interconnected computers that can share data, applications, and resources, such as printers. Computers in a LAN are separated by distances of up to a few kilometers and are typically used in offices or across university campuses. A LAN enables the fast and effective transfer of information within a group of users and reduces operational costs (see Network).

Other connected computer resources are wide area networks (WANs) and private branch exchanges (PBXs). WANs are similar to LANs but they connect computers separated by longer distances, typically across the country or internationally, and they use specialized and expensive hardware and leased communications services. PBXs provide continuous computer connections for the transfer of specialized data such as telephone transmissions, but they are not ideally suited to send and receive the short bursts of data used by most computer applications

History

In the days before personal computers, a site might have just one central computer, with users accessing this via computer terminals over simple low-speed cabling. Networks such as IBM's SNA (Systems Network Architecture) were aimed at linking terminals or other mainframes at remote sites over leased lines—hence these were wide area networks.

The first LANs were created in the late 1970s and used to create high-speed links between several large central computers at one site. Of many competing systems created at this time, Ethernet and ARCNET were the most popular.

The growth of CP/M and then DOS based personal computer meant that a single site began to have dozens or even hundreds of computers. The initial attraction of networking these was generally to share disk space and laser printers, which were both very expensive at the time. There was much enthusiasm for the concept and for several years from about 1983 onward computer industry pundits would regularly declare the coming year to be “the year of the LAN”.

In reality the concept was marred by proliferation of incompatible physical layer and network protocol implementations, and confusion over how best to share resources. Typically each vendor would have their own type of network card, cabling, protocol, and network operating system. A solution appeared with the advent of Novell NetWare which gave: (a) even-handed support for the 40 or so competing card/cable types, and (b) a much more sophisticated operating system than most of its competitors. NetWare dominated the personal computer LAN business from early after its introduction in 1983 until the mid 1990s when Microsoft introduced Windows NT Advanced Server and Windows for Workgroups.

Of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. Microsoft and 3Com worked together to create a simple network operating system which formed the base of 3Com's 3+Share, Microsoft's LAN Manager and IBM's LAN Server. None of these was particularly successful.

In this same timeframe Unix computer workstation from vendors such as Sun Microsystems, Hewlett-Packard, Silicon Graphics, Intergraph, NeXT and Apollo were using TCP/IP based networking. Although this market segment is now much reduced, the technologies developed in this area continue to be influential on the Internet and in both Linux and Apple Mac OS X networking.

See also

• SOHO network
• Campus area network
• Metropolitan area network
• CHAOSnet
• DECnet
• Wireless LAN
• null modem
• LAN party
• Internetworking
• Personal area network
• Home network

References

• Charp, S. (Ed.). (1994). Networking & telecommunications. "T.H.E." ("Technical Horizons in Education"), 21(10). (EJ 483 802-807)
• Charp, S. (Ed.). (1995). Networking & telecommunications. "T.H.E." ("Technical Horizons in Education"), 22(9). (EJ 501 732-735)
• Communications, computers, and networks. (1991). [Special Issue.] "Scientific American," 265(3).
• Ellis, T. I. (1984). "Microcomputers in the school office. ERIC Digest." Syracuse, NY: ERIC Clearinghouse on Education Management. (ED 259 451)
• Klausmeier, J. (1984). "Networking and microcomputers. ERIC Digest." Syracuse, NY: ERIC Clearinghouse on Information Resources. (ED 253 256)
• Neubarth, M. (Ed.). (1995, October). The Internet in education. [Special issue]. "Internet World," 6(10). (ERIC ED pending, IR 531 431-438)
• Rienhold, F. (1989). "Use of local area networks in schools. ERIC Digest." Syracuse, NY: ERIC Clearinghouse on Information Resources. (ED 316 249)

External links

• Local Area Networks for K-12 Schools
• Use of Local Area Networks in Schools.
• Microcomputers in the School Office
• How to Build a Wireless Home Network (Tutorial)
• The Hitchhiker's Guide to the Internet - A comprehensive guide for information on networking, and removing spyware, adware, trojans and viruses