Editing Network switch (section)

== Role in a network ==
Switches are most commonly used as the network connection point for hosts at the edge of a network. In the [[hierarchical internetworking model]] and similar network architectures, switches are also used deeper in the network to provide connections between the switches at the edge.

In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, [[Fibre Channel]], [[RapidIO]], [[Asynchronous Transfer Mode|ATM]], [[ITU-T]] [[G.hn]] and [[802.11]]. This connectivity can be at any of the layers mentioned. While the layer-2 functionality is adequate for bandwidth-shifting within one technology, interconnecting technologies such as Ethernet and [[Token Ring]] is performed more easily at layer 3 or via routing.<ref>{{cite web | url = http://www.redbooks.ibm.com/redpapers/pdfs/redp0168.pdf#page=23 | title = Token-Ring to Ethernet Migration | date = February 2002 | access-date = 2015-08-11 | author1 = Joe Efferson | author2 = Ted Gary | author3 = Bob Nevins | publisher = [[IBM]] | format = PDF | page = 13 | archive-url = https://web.archive.org/web/20150924111914/http://www.redbooks.ibm.com/redpapers/pdfs/redp0168.pdf#page=23 | archive-date = 2015-09-24 | url-status = dead }}</ref> Devices that interconnect at the layer&nbsp;3 are traditionally called [[Router (computing)|routers]].<ref>{{cite web
 | url = http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_1-2/switch_evolution.html
 | title = The Internet Protocol Journal - Volume&nbsp;1, No.&nbsp;2: Layer&nbsp;2 and Layer&nbsp;3 Switch Evolution
 | date = September 1998 | access-date = 2015-08-11
 | author = Thayumanavan Sridhar | publisher = [[Cisco Systems]]
}}</ref>

Where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide [[Firewall (computing)|firewall]],<ref>[http://cisco.com/en/US/products/hw/modules/ps2706/ps4452/index.html Cisco Catalyst 6500 Series Firewall Services Module], Cisco Systems, 2007</ref><ref>[http://www.3com.com/products/en_US/detail.jsp?tab=features&sku=3C17546&pathtype=purchase3Com Switch 8800 Firewall Module], 3Com Corporation, 2006</ref> network [[intrusion detection]],<ref>[http://cisco.com/en/US/products/hw/modules/ps2706/ps5058/index.html Cisco Catalyst 6500 Series Intrusion Detection System (IDSM-2) Module], Cisco Systems, 2007</ref> and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.<ref>[https://web.archive.org/web/20031007183603/http://www.checkpoint.com/support/technical/online_ug/firewall-14.0/config.htm Getting Started with Check Point Fire Wall-1], Checkpoint Software Technologies Ltd., n.d.</ref>

Through [[port mirroring]], a switch can create a mirror image of data that can go to an external device, such as [[intrusion detection system]]s and [[packet sniffer]]s.

A modern switch may implement [[power over Ethernet]] (PoE), which avoids the need for attached devices, such as a [[VoIP phone]] or [[wireless access point]], to have a separate power supply. Since switches can have redundant power circuits connected to [[uninterruptible power supplies]], the connected device can continue operating even when regular office power fails.

In 1989 and 1990, [[Kalpana, Inc.|Kalpana]] introduced the first multiport [[Ethernet]] switch, its seven-port EtherSwitch.<ref name="networkcomputing_2000">{{cite web |title=The 10 Most Important Products of the Decade |author=Robert J. Kohlhepp |date=October 2, 2000 |access-date=February 25, 2008 |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=January 5, 2010}}</ref>