A system for exchanging information across networks that are incompatible and/or use different protocols. Basically, a gateway is a combination of hardware and software that connects two different types of networks so that information can be exchanged. The hardware devices (called "bridges") and the computer programs perform the necessary translations.

The gateway has a name/address in EACH network and has to be running an implementation of each protocol. An Internet gateway (both nets are using the TCP/IP protocol) routes IP datagrams between the networks it connects. Gateways route packets to other gateways until they can be delivered to the final destination directly across one physical network.

For example, you can access the Archie service by way of a Web page that functions as an Archie gateway, and similarly, AOL services have e-mail gateways for sending messages to other e-mail systems.

Separately, a "mobile gateway" is a ground-based link to a mobile satellite service network.