Alocal area network (LAN) is acomputer network that interconnects computers within a limited area such as a residence, campus, or building,[1][2][3] and has itsnetwork equipment and interconnects locally managed. LANs facilitate the distribution of data and sharing network devices, such as printers.
The LAN contrasts thewide area network (WAN), which not only covers a larger geographic distance, but also generally involvesleased telecommunication circuits orInternet links. An even greater contrast is theInternet, which is a system of globally connected business and personal computers.
Ethernet andWi-Fi are the two most common technologies used for local area networks; historical network technologies includeARCNET,Token Ring, andLocalTalk.
Most wired network infrastructures utilizeCategory 5 orCategory 6twisted pair cabling withRJ45 compatible terminations. This medium provides physical connectivity between theEthernet interfaces present on a large number of IP-aware devices. Depending on the grade of cable and quality of installation, speeds of up to 10 Mbit/s, 100 Mbit/s, 1 Gbit/s, or 10 Gbit/s are supported.
In awireless 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, convenience, and flexibility.[4] Most wireless LANs consist of devices containingwireless radio technology that conforms to802.11 standards as certified by theIEEE. Most wireless-capable residential devices operate at both the 2.4GHz and 5 GHz frequencies and fall within the 802.11n or 802.11ac standards.[5] Some older home networking devices operate exclusively at a frequency of 2.4 GHz under 802.11b and 802.11g, or 5 GHz under 802.11a. Some newer devices operate at the aforementioned frequencies in addition to 6 GHz underWi-Fi 6E.Wi-Fi is a marketing and compliance certification for IEEE 802.11 technologies.[6] TheWi-Fi Alliance has tested compliant products, and certifies them for interoperability. The technology may be integrated intosmartphones,tablet computers andlaptops. Guests are often offeredInternet access via ahotspot service.
A conceptual diagram of a LAN at a small business office; this example includes two rooms, each with aswitch, as well as afile server, and a mix of wired and wireless connections. This is thestar topology.
Advanced LANs are characterized by their use of redundant links with switches using theSpanning Tree Protocol to prevent loops, their ability to manage differing traffic types viaquality of service (QoS), and their ability to segregate traffic withVLANs. Anetwork bridge binds two different LANs or LAN segments to each other, often in order to grant a wired-only device access to a wireless network medium.
Network topology describes the layout of interconnections between devices and network segments. At thedata link layer andphysical layer, a wide variety of LAN topologies have been used, includingring,bus,mesh andstar. The star topology is the most common in contemporary times. Wireless LAN (WLAN) also has its topologies: independent basic service set (IBSS, anad-hoc network) where each node connects directly to each other (this is also standardized asWi-Fi Direct), or basic service set (BSS, an infrastructure network that uses anwireless access point).[8]
Various topologies that may be used in a centralised wired LAN: star, ring, bus, and tree
DHCP is used to assign internal IP addresses to members of a local area network. A DHCP server typically runs on the router[9] with end devices as its clients. All DHCP clients request configuration settings using the DHCP protocol in order to acquire theirIP address, adefault route and one or moreDNS server addresses. Once the client implements these settings, it will be able to communicate on thatinternet.[10]
At the higher network layers, protocols such asNetBIOS,IPX/SPX,AppleTalk and others were once common, but theInternet protocol suite (TCP/IP) has prevailed as the standard of choice for almost all local area networks today.
LANs can maintain connections with other LANs via leased lines, leased services, or across theInternet usingvirtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as ametropolitan area network (MAN) or awide area network (WAN).
Local area networks may be connected to theInternet (a type ofWAN) via fixed-line means (such as aDSL/ADSL modem[11]) or alternatively using a cellular or satellitemodem. These would additionally make use of telephone wires such asVDSL andVDSL2, coaxial cables, orfiber to the home for running fiber-optic cables directly into a house or office building, or alternatively a cellular modem orsatellite dish in the latter non-fixed cases. WithInternet access, theInternet service provider (ISP) would grant a single WAN-facingIP address to the network. A router is configured with the provider's IP address on the WAN interface, which is shared among all devices in the LAN bynetwork address translation.
Agateway establishesphysical anddata link layer connectivity to a WAN over a service provider's native telecommunications infrastructure. Such devices typically contain acable,DSL, oroptical modem bound to anetwork interface controller for Ethernet. Home and small business class routers are often incorporated into these devices for additional convenience, and they often also have integratedwireless access point and 4-port Ethernetswitch.
TheITU-TG.hn andIEEEPowerline standard, which provide high-speed (up to 1 Gbit/s) local area networking over existing home wiring, are examples of home networking technology designed specifically forIPTV delivery.[12][relevant?]
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 theLawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation.[13][14]
The development and proliferation ofpersonal computers using theCP/M operating system in the late 1970s, and laterDOS-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 sharestorage andprinters, 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".[22][23][24]
In practice, the concept was marred by the proliferation of incompatiblephysical layer andnetwork protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, andnetwork operating system. A solution appeared with the advent ofNovell 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, onlyBanyan Vines had comparable technical strengths, but Banyan never gained a secure base.3Com produced3+Share and Microsoft producedMS-Net. These then formed the basis for collaboration betweenMicrosoft and 3Com to create a simple network operating systemLAN Manager and its cousin, IBM'sLAN 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 introducedWindows NT.[25]
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.[26][27] The TCP/IP-based LAN successfully supportedTelnet,FTP, and a Defense Department teleconferencing application.[28] This demonstrated the feasibility of employing TCP/IP LANs to interconnectWorldwide Military Command and Control System (WWMCCS) computers at command centers throughout the United States.[29] However, WWMCCS was superseded by theGlobal 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 replacedIPX,AppleTalk,NBF, and other protocols used by the early PC LANs.
Econet was Acorn Computers's low-cost local area network system, intended for use by schools and small businesses. It was first developed for theAcorn Atom andAcorn System 2/3/4 computers in 1981.[30][31]
In the 1980s, several token ring network implementations for LANs were developed.[32][33] IBM released its own implementation of token ring in 1985,[34][35] It ran at4 Mbit/s.[36] IBM claimed that their token ring systems were superior to Ethernet, especially under load, but these claims were debated;[37][38] while the slow but inexpensive AppleTalk was popular for Macs, in 1987InfoWorld said, "No LAN has stood out as the clear leader, even in the IBM world".[39] IBM's implementation of token ring was the basis of the IEEE 802.5 standard.[40] A 16 Mbit/s version of Token Ring was standardized by the 802.5 working group in 1989.[41] IBM had market dominance over Token Ring, for example, in 1990, IBM equipment was the most widely used for Token Ring networks.[42]
Fiber Distributed Data Interface (FDDI), a LAN standard, was considered an attractive campusbackbone 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 includedCisco Systems,National Semiconductor, Network Peripherals, SysKonnect (acquired byMarvell Technology Group), and3Com.[43] FDDI installations have largely been replaced by Ethernet deployments.[44]
^Sadiku, Matthew N. O.; Tembely, Mahamadou; Musa, Sarhan M. (2017-05-30)."Home Area Networks: A Primer"(PDF).International Journal of Advanced Research in Computer Science and Software Engineering.7 (5):634–635.doi:10.23956/ijarcsse/SV7I5/208 (inactive 11 October 2025). Archived fromthe original(PDF) on 2017-07-09.{{cite journal}}: CS1 maint: DOI inactive as of October 2025 (link)
^Berger, Lars T.; Schwager, Andreas; Pagani, Pascal; Van Rensburg; Piet Janse (February 2014)."Introduction to the Power Line Communication Channel and Noise Characterisation". In Berger, Lars T.; Schwager, Andreas; Pagani, Pascal; Schneider, Daniel M (eds.).MIMO Power Line Communications: Narrow and Broadband Standards, EMC, and Advanced Processing. Devices, Circuits, and Systems. CRC Press. pp. 3–38.doi:10.1201/b16540-3.ISBN9781466557529.Archived from the original on 2015-10-17. Retrieved2014-05-19.
^Metcalfe, Robert (Dec 27, 1993)."Will The Year of the ISDN be 1994 or 1995?".InfoWorld.15 (52).Archived from the original on June 14, 2021. RetrievedJune 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...
^"Quotes in 1999".Cafe au Lait Java News and Resources.Archived from the original on 2016-04-14. Retrieved2011-02-25....you will remember numerous computer magazines, over numerous years, announcing 'the year of the LAN.'
^Herot, Christopher."Christopher Herot's Weblog". Retrieved2023-10-21....a bit like the Year of the LAN which computer industry pundits predicted for the good part of a decade...
^Scott, W. Ross (May 1, 1984). "Updated Local Area Network Demonstration Plan".MITRE Corporation Working Paper (WP83W00222R1).
^Havard (II.), Richard (17 June 1986).MITRENET: A Testbed Local Area Network at DTNSRDC. Ft. Belvoir Defense Technical Information Center: Defense Technical Information Center. p. i.
^Scott, W. Ross; Cavedo, Robert F. (September 1, 1984). "Local Area Network Demonstration Procedures".MITRE Corporation Working Paper (WP83W00595).
^Scott, W. Ross (August 1, 1984). "Local Area Network Alternative "A" Demonstration Analysis (DRAFT)".MITRE Corporation Working Paper (WP84W00281).
