Editing Network switch (section)

{{Technical|introduction|date=May 2024}}
{{Short description|Networking hardware that forwards packets based on hardware address}}
{{Use American English|date = March 2019}}

[[File:2550T-PWR-Front.jpg|thumb|upright=1.7|[[Avaya]] [[ERS 3500 and ERS 2500 series|ERS 2550T-PWR]], a 50-port [[Ethernet]] switch]]

A '''network switch''' (also called '''switching hub''', '''bridging hub''', '''Ethernet switch''', and, by the [[IEEE]], '''MAC bridge'''<ref>IEEE 802.1D</ref>) is [[networking hardware]] that connects devices on a [[computer network]] by using [[packet switching]] to receive and forward data to the destination device.

A network switch is a multiport [[network bridge]] that uses [[MAC address]]es to forward data at the [[data link layer]] (layer 2) of the [[OSI model]]. Some switches can also forward data at the [[network layer]] (layer 3) by additionally incorporating [[routing]] functionality. Such switches are commonly known as layer-3 switches or [[multilayer switch]]es.<ref name=layer3>{{cite web|author=Thayumanavan Sridhar |url=http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_1-2/switch_evolution.html |title=Layer 2 and Layer 3 Switch Evolution |series=The Internet Protocol Journal |volume=1 |issue=2 |publisher=Cisco Systems |website=cisco.com |date=September 1998 |access-date=2014-08-05}}</ref>

Switches for [[Ethernet]] are the most common form of network switch. The first MAC Bridge<ref>{{Cite journal|last1=Stewart|first1=Robert|last2=Hawe|first2=William|last3=Kirby|first3=Alan|date=April 1984|title=Local Area Network Connection|journal=Telecommunications}}</ref><ref>W. Hawe, A. Kirby, A. Lauck, "An Architecture for Transparently Interconnecting IEEE 802 Local Area Networks", technical paper submitted to the IEEE 802 committee, document IEEE-802.85*1.96, San Diego CA, October 1984.</ref><ref>{{Cite book|last1=Hawe|first1=William|title=Advances in Local Area Networks|last2=Kirby|first2=Alan|last3=Stewart|first3=Robert|publisher=IEEE Press|year=1987|isbn=0-87942-217-3|pages=Chapter 28}}</ref> was invented<ref>{{cite patent |title=Bridge circuit for interconnecting networks |country=US |number=4597078}}</ref> in 1983 by Mark Kempf, an engineer in the Networking Advanced Development group of [[Digital Equipment Corporation]]. The first 2 port Bridge product (LANBridge 100) was introduced by that company shortly after.  The company subsequently produced multi-port switches for both Ethernet and [[FDDI]] such as GigaSwitch.  Digital decided to license its MAC Bridge patent in a royalty-free, non-discriminatory basis that allowed IEEE standardization.  This permitted a number of other companies to produce multi-port switches, including [[Kalpana, Inc.|Kalpana]].<ref>{{cite web |title=The 10 Most Important Products of the Decade |author=Robert J. Kohlhepp |date=2000-10-02 |access-date=2008-02-25 |publisher=Network Computing |url=http://www.networkcomputing.com/1119/1119f1products_5.html |archive-url=https://web.archive.org/web/20100105152318/http://www.networkcomputing.com/1119/1119f1products_5.html |archive-date=2010-01-05}}</ref> Ethernet was initially a [[Shared medium|shared-access medium]], but the introduction of the MAC bridge began its transformation into its most-common point-to-point form without a [[collision domain]].  Switches also exist for other types of networks including [[Fibre Channel]], [[Asynchronous Transfer Mode]], and [[InfiniBand]].

Unlike [[repeater hub]]s, which broadcast the same data out of each port and let the devices pick out the data addressed to them, a network switch learns the Ethernet addresses of connected devices and then only forwards data to the port connected to the device to which it is addressed.<ref>{{cite web
 | url = http://www.ccontrols.com/pdf/Extv3n3.pdf
 | title = Hubs Versus Switches – Understand the Tradeoffs
 | year = 2002 | access-date = 2013-12-10
 | website = ccontrols.com }}</ref>