Editing Local area network (section)

== Infrastructure and technicals ==
[[File:Simple_LAN_example_diagram_in_two_rooms.png|thumb|A conceptual diagram of a LAN at a small business office; this example includes two rooms, each with a [[Network switch|switch]], as well as a [[file server]], and a mix of wired and wireless connections. This is the [[star topology]].]]
Simple LANs in office or school buildings generally consist of cabling and one or more [[network switch]]es; a switch is used to allow devices on a LAN to talk to one another via [[Ethernet]]. A switch can be connected to a [[Router (computing)|router]], [[cable modem]], or [[ADSL modem]] for [[Internet]] access. LANs at residential homes usually tend to have a single router and often may include a [[wireless repeater]]. A LAN can include a wide variety of other network devices such as [[Firewall (computing)|firewall]]s, [[Load balancing (computing)|load balancers]], and [[Network intrusion detection system|network intrusion detection]].<ref>{{cite web |title=A Review of the Basic Components of a Local Area Network (LAN) |url=http://networkbits.net/lan-components/local-area-network-lan-basic-components/ |url-status=usurped |archive-url=https://web.archive.org/web/20201026082752/http://networkbits.net/lan-components/local-area-network-lan-basic-components/ |archive-date=2020-10-26 |access-date=2008-04-08 |publisher=NetworkBits.net}}</ref> A [[wireless access point]] is required for connecting wireless devices to a network; when a router includes this device, it is referred to as a [[wireless router]].

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 [[VLAN]]s. A [[network 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 the [[data link layer]] and [[physical layer]], a wide variety of LAN topologies have been used, including [[ring network|ring]], [[bus network|bus]], [[mesh network|mesh]] and [[star network|star]]. The star topology is the most common in contemporary times. Wireless LAN (WLAN) also has its topologies: independent basic service set (IBSS, an [[Wireless ad hoc network|ad-hoc network]]) where each node connects directly to each other (this is also standardized as [[Wi-Fi Direct]]), or basic service set (BSS, an infrastructure network that uses an [[wireless access point]]).<ref>{{Cite web |url=https://www3.nd.edu/~mhaenggi/NET/wireless/802.11b/topology.htm |title=Network Topologies |access-date=2024-12-11 |website=www3.nd.edu}}</ref>[[File:LAN topology.gif|thumb|Various topologies that may be used in a centralised wired LAN: star, ring, bus, and tree|400x400px|center]]

=== Network layer configuration ===
[[Dynamic Host Configuration Protocol|DHCP]] is used to assign internal IP addresses to members of a local area network. A DHCP server typically runs on the router<ref>[http://www.whatismyip.com/ip-faq/what-is-dhcp/ What is DHCP?] {{Webarchive|url=https://web.archive.org/web/20131207234400/http://www.whatismyip.com/ip-faq/what-is-dhcp/|date=2013-12-07}}. whatismyip.com.</ref> with end devices as its clients. All DHCP clients request configuration settings using the DHCP protocol in order to acquire their [[IP address]], a [[default route]] and one or more [[DNS server]] addresses. Once the client implements these settings, it will be able to communicate on that [[Internetwork|internet]].<ref>{{Cite journal |last1=Roy G. Perry College of Engineering, Prairie View A&M University, Prairie View, TX 77446, United States |last2=Sadiku |first2=Matthew N. O. |last3=Tembely |first3=Mahamadou |last4=Roy G. Perry College of Engineering, Prairie View A&M University, Prairie View, TX 77446, United States |last5=Musa |first5=Sarhan M. |last6=Roy G. Perry College of Engineering, Prairie View A&M University, Prairie View, TX 77446, United States |date=2017-05-30 |title=Home Area Networks: A Primer |url=http://ijarcsse.com/docs/papers/Volume_7/5_May2017/SV7I5-0208.pdf |journal=International Journal of Advanced Research in Computer Science and Software Engineering |volume=7 |issue=5 |pages=634–635 |doi=10.23956/ijarcsse/SV7I5/208 |doi-broken-date=2024-11-12}}</ref>

=== Protocols ===
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 for almost all local area networks today.

=== Connection to other LANs ===
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).

=== Connection to the Internet ===
Local area networks may be connected to the [[Internet]] (a type of [[Wide area network|WAN]]) via fixed-line means (such as a [[DSL]]/[[ADSL]] modem<ref>{{Cite web |title=Configuration example for connecting a LAN to the Internet through an ADSL modem |url=https://support.hpe.com/techhub/eginfolib/networking/docs/routers/hsr6800/5200-3506_l2-wan_cg/content/482615561.htm |access-date=2024-12-06 |website=support.hpe.com}}</ref>) or alternatively using a cellular or satellite [[modem]]. These would additionally make use of telephone wires such as [[Very High Speed Digital Subscriber Line|VDSL]] and [[Very High Speed Digital Subscriber Line 2|VDSL2]], coaxial cables, or [[fiber to the home]] for running fiber-optic cables directly into a house or office building, or alternatively a cellular modem or [[satellite dish]] in the latter non-fixed cases. With [[Internet access]], the [[Internet service provider|Internet service provider (ISP)]] would grant a single WAN-facing [[IP 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 by [[network address translation]]. 

A [[Residential gateway|gateway]] establishes [[Physical layer|physical]] and [[data link layer]] connectivity to a WAN over a service provider's native telecommunications infrastructure. Such devices typically contain a [[Cable modem|cable]], [[DSL modem|DSL]], or [[Modem#Optical modem|optical modem]] bound to a [[network interface controller]] for Ethernet. Home and small business class routers are often incorporated into these devices for additional convenience, and they often also have integrated [[wireless access point]] and 4-port Ethernet [[LAN switching|switch]]. 

The [[ITU-T]] [[G.hn]] and [[IEEE]] [[Power line communication|Powerline]] standard, which provide high-speed (up to 1&nbsp;Gbit/s) local area networking over existing home wiring, are examples of home networking technology designed specifically for [[Internet Protocol television|IPTV]] delivery.<ref name="BERGU142">{{cite book |author1=Berger, Lars T. |title=MIMO Power Line Communications: Narrow and Broadband Standards, EMC, and Advanced Processing |author2=Schwager, Andreas |author3=Pagani, Pascal |author4=Van Rensburg |author5=Piet Janse |date=February 2014 |publisher=CRC Press |isbn=9781466557529 |editor1=Berger, Lars T. |series=Devices, Circuits, and Systems |pages=3–38 |chapter=Introduction to the Power Line Communication Channel and Noise Characterisation |doi=10.1201/b16540-3 |access-date=2014-05-19 |editor2=Schwager, Andreas |editor3=Pagani, Pascal |editor4=Schneider, Daniel M |chapter-url=http://www.crcnetbase.com/doi/abs/10.1201/b16540-3?queryID= |archive-url=https://web.archive.org/web/20151017135609/http://www.crcnetbase.com/doi/abs/10.1201/b16540-3?queryID= |archive-date=2015-10-17 |url-status=live}}</ref>{{Relevance inline|date=December 2024}}