Session control using a multicast address

摘要

A method ( 800, 900 ) and apparatus ( 1001 ) for controlling a session between communication units ( 141 - 146 ) sharing a group Internet Protocol (IP) multicast address. The method includes determining communication units from which a response to a session initiation protocol (SIP) control message is not required and preparing the control message which is sent to the communication units using the group address with information used to control from which of the of communication units the response is required. The SIP control message is sent to a second communication unit using a unicast address indicating that the response is required.