Gateway

A gateway is a device that is used to connect one type of network to another. For example, a gateway is used to connect the legacy ▲PSTN network to the ▲VoIP networks that are now being deployed. The gateway's responsibility is to provide signaling interworking, as well as transforming the bearer information (e.g., "what you hear on the phone") into a format that is suitable for the other network.

A gateway may exist as a single monolithic device or it may be decomposed into logical components. A gateway is viewed as a device that has a Signaling Gateway part, a ▲Media Gateway part, and a ▲Media Gateway Controller part.