simple gateway control protocol (SGCP)
The Simple Gateway Control Protocol (SGCP) is one of the first gateway protocols for Internet telephony and, like the MGCP protocol, MEGACO/H.248, is used to connect circuit-switched telephone networks with packet-switched IP networks. SGCP uses master- slave operation with a softswitch as master and uses it to control connections for Internet telephony( VoIP).
SGCP, which uses the UDP protocol as its transport protocol, is designed as a simple protocol for remote control. In this case, the softswitches receive their information for controlling the gateways via signaling protocols such as the Session Initiation Protocol( SIP), ISDN User Part( ISUP) or H.323.
The SGCP protocol knows the following commands: Create Connection for establishing a connection, Modify Connection for changing it, Delete Connection for deleting the connection, Notification Request for a request and Notify. The first four commands are sent to the gateway by the call agents. The Notify command is sent from the gateway to the call agents. All commands are composed of the command header, optionally followed by the description for the session.