Engineering:Local area network

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Short description: Computer network that connects devices over a limited area
A conceptual diagram of a local area network using bus network topology

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.[1] By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits.

Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical network technologies include ARCNET, Token Ring and AppleTalk.


The increasing demand and usage of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation.[2][3]

A number of experimental and early commercial LAN technologies were developed in the 1970s. Ethernet was developed at Xerox PARC between 1973 and 1974.[4][5] Cambridge Ring was developed at Cambridge University starting in 1974.[6] ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977.[7] It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.[8] In 1979,[9] the Electronic voting systems for the European Parliament was the first installation of a LAN connecting hundreds (420) of microprocessor-controlled voting terminals to a polling/selecting central unit with a multidrop bus with Master/slave (technology) arbitration.

The development and proliferation of personal computers using the CP/M operating system in the late 1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was to share storage and printers, both of which were expensive at the time. There was much enthusiasm for the concept, and for several years, from about 1983 onward, computer industry pundits habitually declared the coming year to be, "The year of the LAN".[10][11][12]

In the 1980s, several token ring network implementations for LANs were developed.[13][14] IBM released their own implementation of token ring in 1985,[15][16] IBM claimed that their token ring systems were superior to Ethernet, especially under load, but these claims were debated.[17][18] IBM's implementation of token ring was the basis of the IEEE 802.5 standard.[19] A 16 Mbit/s version of Token Ring was standardized by the 802.5 working group in 1989.[20] IBM had market dominance over Token Ring, for example, in 1990, IBM equipment was the most widely used for Token Ring networks.[21]

In practice, the concept was marred by the proliferation of incompatible physical layer and network protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. A solution appeared with the advent of Novell NetWare which provided even-handed support for dozens of competing card and cable types, and a much more sophisticated operating system than most of its competitors.

Of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. 3Com produced 3+Share and Microsoft produced MS-Net. These then formed the basis for collaboration between Microsoft and 3Com to create a simple network operating system LAN Manager and its cousin, IBM's LAN Server. None of these enjoyed any lasting success; Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT.[22]

In 1983, TCP/IP was first shown capable of supporting actual defense department applications on a Defense Communication Agency LAN testbed located at Reston, Virginia.[23][24] The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department teleconferencing application.[25] This demonstrated the feasibility of employing TCP/IP LANs to interconnect Worldwide Military Command and Control System (WWMCCS) computers at command centers throughout the United States.[26] However, WWMCCS was superseded by the Global Command and Control System (GCCS) before that could happen.

During the same period, Unix workstations were using TCP/IP networking. Although the workstation market segment is now much reduced, the technologies developed in the area continue to be influential on the Internet and in all forms of networking—and the TCP/IP protocol has replaced IPX, AppleTalk, NBF, and other protocols used by the early PC LANs.

Fiber Distributed Data Interface (FDDI), a LAN standard, was considered an attractive campus backbone network technology in the early to mid 1990s since existing Ethernet networks only offered 10 Mbit/s data rates and Token Ring networks only offered 4 Mbit/s or 16 Mbit/s rates. Thus it was a relatively high-speed choice of that era, with speeds such as 100 Mbit/s. By 1994, vendors included Cisco Systems, National Semiconductor, Network Peripherals, SysKonnect (acquired by Marvell Technology Group), and 3Com.[27] FDDI installations have largely been replaced by Ethernet deployments.[28]


Twisted pair LAN cable

In 1979,[9] the Electronic voting systems for the European Parliament was using 10 kilometers of simple unshielded twisted pair category 3 cable—the same cable used for telephone systems—installed inside the benches of the European Parliament Hemicycles in Strasbourg and Luxembourg.[29]

Early Ethernet (10BASE-5 and 10BASE-2) used coaxial cable. Shielded twisted pair was used in IBM's Token Ring LAN implementation. In 1984, StarLAN showed the potential of simple unshielded twisted pair by using category 3 cable—the same cable used for telephone systems. This led to the development of 10BASE-T (and its twisted-pair successors) and structured cabling which is still the basis of most commercial LANs today.

While optical fiber cable is common for links between network switches, use of fiber to the desktop is rare.[30]

Wireless media

In a wireless LAN, users have unrestricted movement within the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Most wireless LANs use Wi-Fi as wireless adapters are typically integrated into smartphones, tablet computers and laptops. Guests are often offered Internet access via a hotspot service.

Technical aspects

Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star.

Simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, or ADSL modem for Internet access. A LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection.[31] Advanced LANs are characterized by their use of redundant links with switches using the spanning tree protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and their ability to segregate traffic with VLANs.

At the higher network layers, protocols such as NetBIOS, IPX/SPX, AppleTalk and others were once common, but the Internet protocol suite (TCP/IP) has prevailed as the standard of choice.

LANs can maintain connections with other LANs via leased lines, leased services, or across the Internet using virtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network (MAN) or a wide area network (WAN).

See also


  1. Gary A. Donahue (June 2007). Network Warrior. O'Reilly. p. 5. 
  2. Samuel F. Mendicino (1970-12-01). "Octopus: The Lawrence Radiation Laboratory Network". 
  3. Mendicino, S. F. (29 Nov 1970). "THE LAWRENCE RADIATION LABORATORY OCTOPUS". Courant Symposium Series on Networks ( 
  4. Archived at Ghostarchive and the Wayback Machine: The History of Ethernet. 2006. Retrieved September 10, 2011.
  5. "Ethernet Prototype Circuit Board". Smithsonian National Museum of American History. 1973. 
  6. "A brief informal history of the Computer Laboratory". University of Cambridge. 20 December 2001. 
  7. "ARCNET Timeline". ARCNETworks magazine. Fall 1998. 
  8. Lamont Wood (2008-01-31). "The LAN turns 30, but will it reach 40?". Computerworld. 
  9. 9.0 9.1 European Parliament Archives (January 25, 2021). "Archivist". 
  10. Metcalfe, Robert (Dec 27, 1993). "Will The Year of the ISDN be 1994 or 1995?". InfoWorld 15 (52). Retrieved June 14, 2021. "'The Year of The LAN' is a long-standing joke, and I freely admit to being the comedian that first declared it in 1982...". 
  11. "Quotes in 1999". " will remember numerous computer magazines, over numerous years, announcing 'the year of the LAN.'" 
  12. Herot, Christopher. "Christopher Herot's Weblog". "...a bit like the Year of the LAN which computer industry pundits predicted for the good part of a decade..." 
  13. J. Noel Chiappa (April–June 2014). "Early Token Ring Work at MIT". IEEE Annals of the History of Computing 36 (2): 80–85. doi:10.1109/MAHC.2014.14. 
  14. Pelkey, James. "14.18 Proteon in Chapter 14 - Internetworking: Emergence 1985-1988". The History of Computer Communications. 
  15. "IBM TOKEN-RING NETWORK" (in en-US). 1985-10-15. 
  16. Crabb, Don (24 March 1986). "Major Vendors Differ On Network Approach". InfoWorld 8 (12): 27. 
  17. IEEE 802.3 Local Area Network considerations. IBM. GG22-9422-0. 
  18. David R. Boggs; Jeffrey C. Mogul; Christopher A. Kent (1988). "Measured capacity of an Ethernet: myths and reality". ACM SIGCOMM Computer Communication Review 25 (1): 123–136. doi:10.1145/205447.205460. 
  19. Internetworking Technologies Handbook. 2004. ISBN 9781587051197. 
  20. "IEEE Standards Association". 
  21. Urs Von Burg; Martin Kenny (December 2003). "Sponsers, [sic Communities, and Standards: Ethernet vs. Token Ring In The Local Area Networking Business"]. Industry and Innovation (Taylor & Francis Ltd) 10 (4): 351–375. doi:10.1080/1366271032000163621.,%20Communities,%20and%20Standards_%20Ethernet%20vs.%20Token%20Ring%20in%20the%20Local%20Area%20Networking%20Business.pdf. 
  22. Wayne Spivak (2001-07-13). "Has Microsoft Ever Read the History Books?". VARBusiness. 
  23. Scott, W. Ross (May 1, 1984). "Updated Local Area Network Demonstration Plan". MITRE Corporation Working Paper (WP83W00222R1). 
  24. Havard (II.), Richard (17 June 1986). MITRENET: A Testbed Local Area Network at DTNSRDC.. Ft. Belvoir Defense Technical Information Center: Defense Technical Information Center. pp. i. 
  25. Scott, W. Ross; Cavedo, Robert F. (September 1, 1984). "Local Area Network Demonstration Procedures". MITRE Corporation Working Paper (WP83W00595). 
  26. Scott, W. Ross (August 1, 1984). "Local Area Network Alternative "A" Demonstration Analysis (DRAFT)". MITRE Corporation Working Paper (WP84W00281). 
  27. Mark Miller (March 21, 1994). "Wading Through Plethora of Options Poses Challenge for Life on the Fast LAN". Network World: pp. 41, 44, 46–49. 
  28. A. Selvarajan, Subrat Kar, T. Srinivas (2003). Optical Fiber Communication: Principles and Systems. Tata McGraw-Hill Education. pp. 241–249. ISBN 9781259082207. 
  29. "Italian TV network RAI on the voting system". 25 January 2021. 
  30. "Big pipe on campus: Ohio institutions implement a 10-Gigabit Ethernet switched-fiber backbone to enable high-speed desktop applications over UTP copper", Communications News, 2005-03-01,, "As alternatives were considered, fiber to the desk was evaluated, yet only briefly due to the added costs for fiber switches, cables and NICs. "Copper is still going to be a driving force to the desktop for the future, especially as long as the price for fiber components remains higher than for copper."" 
  31. "A Review of the Basic Components of a Local Area Network (LAN)". 

External links