Media Gateway Control Protocol (MGCP) is a procedure used in VoIP (Voice over IP) systems. This was created to cater to the needs of carrier-based IP telephony networks. MGCP is a protocol that corresponds to H.323 and SIP, devised as an internal system between the Media Gateway (MG) and Media Gateway Controller (MGC).

An MGC manages all call processing by connecting to the IP network through continuous communication with an IP signaling tool. An example of such is an H.323 gatekeeper or SIP server.

MGCP is composed of one Call Agent (CA), MG (to perform media signal conversion between packets and circuits), and Signaling Gateway (SG). They all connect to a PSTN (Public Switched Telephone Network). MGCP is mostly within a decomposed multimedia gateway. This gateway has a CA composed of the call control ‘nucleus’ and a media gateway which operates media functions.

MGs have multimedia endpoints with which the CA creates and manages media sessions with other endpoints. Endpoints are data sources or data sinks that can be either virtual or physical. Hardware installation is required to generate physical endpoints while creating virtual endpoints need software installation.

CAs have the capacity to produce new connections or alter an existing one. Broadly, a media gateway is a component that offers conversion between Internet data packets (or other network packets) and voice transmissions carried by phone lines. The CA gives instructions to endpoints to detect events and create signals. Endpoints intend to convey variations in service state to the CA mechanically. The CA then examines endpoints and the associations between endpoints.