(1) A device that converts one protocol or format to another. A network gateway converts packets from one protocol to another. An application gateway converts commands and/or data from one format to another. An e-mail gateway converts messages from one mail format to another. See IP gateway, proxy server, cable/DSL gateway, default gateway, media gateway, NAS gateway, wireless gateway, messaging gateway, signaling gateway, WAP gateway, softswitch, EGP, BGP and IGP.

(2) A device that acts as a go-between two or more networks that use the same protocols. In this case, the gateway functions as an entry/exit point to the network. Transport protocol conversion may not be required, but some form of processing is typically performed. See proxy server.

(3) An earth station and computer complex that switches data and voice signals between satellites and terrestrial networks.

(4) An earlier name for router. See router and layer 3 switch.

(5) See Gateway Computer.