Patent ID: 7817599

Claim:
A method comprising steps of: (a) assigning a local source address to a mobile station in a telecommunication system wherein the telecommunication system includes a home domain, a visited domain, and a multicast group wherein the multicast group is identified by a multicast address; (b) assigning a home address to the mobile station; (c) detecting a current domain of the mobile station wherein the current domain is only one of the home domain and the visited domain and wherein the current domain is detected using a subnet identifier that identifies the current domain; and (d) responsive to detecting the current domain, switching between using the local source address and using the home address as a source address when sending a packet from the mobile station to the multicast address for communicating with the multicast group and when a comparison result indicates that the mobile station roams between the home domain and the visited domain, wherein using the local source address as the source address for the packet when the current domain is the home domain and using the home address as the source address for the packet when the current domain is the visited domain.