Patent ID: 8400953

Claim:
A method of connecting a call between a local area network and a wide area network, the method comprising the acts of: receiving a call request by a network element of the local area network from a communication unit in the local area network; determining, by the network element of the local area network, that the call request includes an identification of a communication unit supported by the wide area network; accessing in response to the received call request, by the network element of the local area network via a proxy server of the local area network and a gateway of the wide area network, presence information for the communication unit supported by the wide area network from a network element of the wide area network; and establishing the call by the network element of the local area network between the communication unit supported by the local area network and the communication unit supported by the wide area network according to the presence information accessed in response to the received call request, wherein the proxy server of the local area network maps a first call control protocol of the local area network with a second call control protocol of the wide area network, and wherein the established call is a half-duplex push-to-talk call.