Local area network
LAN redirects here, for other uses see LAN (disambiguation). |
Local area network scheme |
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 home, office, or college. Current LANs are most likely to be based on switched
Ethernet or
Wi-Fi technology running at 10, 100 or 1,000
Mbit/s.
The defining characteristics of LANs in contrast to
WANs (wide area networks) are: their much higher data rates; smaller geographic range; and that they do not require leased telecommunication lines.
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.
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 were 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, and the TCP/IP protocol has now almost completely replaced
IPX,
AppleTalk,
NETBEUI and other protocols used by the early PC LANs.
*
SOHO network*
Campus area network*
Metropolitan area network*
CHAOSnet*
DECnet*
Wireless LAN*
null modem*
LAN party*
Internetworking*
Personal area network*
Home network*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)
*
Local Area Networks for K-12 Schools*
Use of Local Area Networks in Schools.*
Microcomputers in the School Office*
Techworld explores the changing nature of the LAN
