US Patent 7450565 Conversational bearer negotiation

A method of setting up a call between first and second nodes of a communication system when the call extends across a circuit switched access network and a packet switched backbone network interconnected by a Media Gateway. A control node obtains from a Home Subscriber Server, the identity of a Media Gateway Control Function controlling that Media Gateway which will terminate the call within the circuit switched access network. The first node calls an access number notified to it by the Media Gateway Control Function, and as part of the call setup procedure, the identity of the Media Gateway selected to terminate the call is communicated to the second node.