gateway

An intermediate system (interface, relay) that attaches to two (or more) computer networks that have similar functions but dissimilar implementations and that enables either one-way or two- way communication between the networks. (See: bridge, firewall, guard, internetwork, proxy server, router, and subnetwork.)

Tutorial: The networks may differ in any of several aspects, including protocols and security mechanisms. When two computer networks differ in the protocol by which they offer service to hosts, a gateway may translate one protocol into the other or otherwise facilitate interoperation of hosts (see: Internet Protocol). In theory, gateways between computer networks are conceivable at any OSIRM layer. In practice, they usually operate

at OSIRM Layer 2 (see: bridge), 3 (see: router), or 7 (see: proxy server).