Architecture
The Media Gateway Control Protocol architecture and its methodologies and programming interfaces are described in RFC 2805.
MGCP is a master/slave protocol that allows a call control device such as a Call Agent to take control of a specific port on a Media Gateway. In MGCP context Media Gateway Controller is referred to as Call Agent. This has the advantage of centralized gateway administration and provides for largely scalable IP Telephony solutions. The distributed system is composed of a Call Agent, at least one Media Gateway (MG) that performs the conversion of media signals between circuits and packets switched networks, and at least one Signaling gateway (SG) when connected to the PSTN (conversion from TDM voice to Voice over IP).
MGCP assumes a call control architecture where there is limited intelligence at the edge (endpoints, Media Gateways) and intelligence at the core Call Agent. The MGCP assumes that Call Agents, will synchronize with each other to send coherent commands and responses to the gateways under their control.
The Call Agent uses MGCP to tell the Media Gateway which events should be reported to the Call Agent, how endpoints should be inter-connected, and which signals should be activated on the endpoints.
MGCP also allows the Call Agent to audit the current state of endpoints on a Media Gateway.
The Media Gateway uses MGCP to report events, such as off-hook or dialed digits, to the Call Agent.
While any signaling gateway is usually on the same physical switch as a media gateway, there is no such need. The Call Agent does not use MGCP to control the Signaling Gateway; rather, SIGTRAN protocols are used to backhaul signaling between the Signaling Gateway and Call Agent.
Read more about this topic: Media Gateway Control Protocol (MGCP)
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