7. Workflow Example

To illustrate how all these pieces work together, let’s walk through a call setup and teardown sequence using MGCP in a simple scenario: Subscriber A, on an analog line at Gateway 1, calls Subscriber B, on an analog line at Gateway 2. A single MGCP Call Agent controls both media gateways. We’ll highlight key MGCP message exchanges and component actions in order:

Initial Conditions: The call agent (CA) controls two gateways (GW1 and GW2). Both gateways have registered their endpoints (say gw1:aaln/1 for subscriber A’s line, gw2:aaln/1 for subscriber B’s line – “aaln” denotes analog line). The gateways have likely sent a RestartInProgress (RSIP) on startup to inform the CA of endpoint availability. The Call Agent “knows” subscriber A’s line is idle and ready. Subscriber A goes off-hook to place a call.