Network switch

The first MAC Bridge[3][4][5] was invented[6] in 1983 by Mark Kempf, an engineer in the Networking Advanced Development group of Digital Equipment Corporation.

Digital decided to license its MAC Bridge patent in a royalty-free, non-discriminatory basis that allowed IEEE standardization.

[7] Ethernet was initially a 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.

Multiple data cables are plugged into a switch to enable communication between different networked devices.

This allows computers to have dedicated bandwidth on point-to-point connections to the network and also to run in full-duplex mode.

In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband technology.

These modules often contain a transceiver that connects the switch to a physical medium, such as a fiber optic cable.

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, ATM, ITU-T G.hn and 802.11.

[20] 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,[21][22] network intrusion detection,[23] and performance analysis modules that can plug into switch ports.

Bridges also buffer an incoming packet and adapt the transmission speed to that of the outgoing port.

In contrast to routers, spanning tree bridges must have topologies with only one active path between two points.

[26][27] Switches are available in many form factors, including stand-alone, desktop units which are typically intended to be used in a home or office environment outside a wiring closet; rack-mounted switches for use in an equipment rack or an enclosure; DIN rail mounted for use in industrial environments; and small installation switches, mounted into a cable duct, floor box or communications tower, as found, for example, in fiber to the office infrastructures.