Definition of switch in The Network Encyclopedia.

What is a switch?

Any device that can control the flow of electrical signals. A number of special-purpose switches are used in networking. For example, the following types of switches are used to control access to computers by printers, keyboards, and monitors:

  • Matrix switches:
    Have a keypad for mapping input ports to output ports and are typically used to connect several printers to several workstations


  • Code-operated switches:
    Use a data string sent by the PC to select the printer port to be used


  • Port-contention or scanning switches:
    Use several input ports but only one output port and monitor the input ports continually for data to route to the output port


  • KVM switches:
    Allow one keyboard/video-monitor/mouse to be used for several servers



In the context of controlling data flow within a network, the term “switch” is also used to describe a data-link layer device that routes frames between connected networks. Data flow switches include

  • Local area network (LAN) switches:
    Used to route Ethernet frames over a TCP/IP internetwork; also called Ethernet switches


  • Asynchronous Transfer Mode (ATM) switches:
    Used to switch ATM cells at high speeds over an ATM network


In the context of high-speed Ethernet networks, the term “switch” usually refers to an Ethernet switch. Thus, the phrase “routers and switches” is understood to mean “routers and Ethernet switches.”

The term “switch” can also refer to a device used at a telco central office (CO) for establishing connections in circuit-switched services or for forwarding packets in packet-switched services.