Media Gateway Control Protocol

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The Media Gateway Control Protocol (MGCP) is a telecommunication protocol for signaling and call control in hybrid voice over IP (VoIP) and traditional telecommunication systems. It implements the media gateway control protocol architecture for controlling media gateways connected to the public switched telephone network (PSTN).^[1] The media gateways provide conversion of traditional electronic media to the Internet Protocol (IP) network. The protocol is a successor to the Simple Gateway Control Protocol (SGCP), which was developed by Bellcore and Cisco, and the Internet Protocol Device Control (IPDC).^[2]

The methodology of MGCP reflects the structure of the PSTN with the control over the network residing in a call control center softswitch, which is analogous to the central office in the telephone network. The endpoints are low-intelligence devices, mostly executing control commands from a media gateway controller, also called call agent, in the softswitch and providing result indications in response. The protocol represents a decomposition of other VoIP models, such as H.323 and the Session Initiation Protocol (SIP), in which the endpoint devices of a call have higher levels of signaling intelligence.

MGCP is a text-based protocol consisting of commands and responses. It uses the Session Description Protocol (SDP) for specifying and negotiating the media streams to be transmitted in a call session and the Real-time Transport Protocol (RTP) for framing the media streams.