A Gateway is an optional component in an H.323enabled network. When communication is required between different networks (e.g. between an IPbased network and PSTN) a gateway is needed at the interface. A H.323 Gateway is an H.323 endpoint that provides for realtime, twoway communications between terminals belonging to networks with different protocol stacks.

For example, it is possible for an H.323 terminal to set up conference with terminals based on H.320 or H.324 through an appropriate gateway.

A gateway provides data format translation, control signaling translation, audio and video codec translation, and call setup and termination functionality on both sides of the network. Depending on the type of network to which translation is required a gateway may support H.310, H.320, H.321, H.322, or H.324 endpoints.