Patent ID: 8166520

Claim:
A method of handling invites to a multi-user communication session employing the IP Multimedia Subsystem to setup and control the session, wherein user access is controlled by two or more user access servers within the IP Multimedia Subsystem, the method comprising: receiving a session invitation at a first user access server from a session initiating user, the invitation identifying as a potential participant at least one user group which is owned by a second user access server; sending an invitation to the second user access server, the invitation including an identification of said user group; at said second user access server, resolving the group identification into a set of group member identities, wherein each group member identity in said set of group member identities is different for each different member in said user group; sending a response containing said group member identities to said first user access server; and at said first user access server, sending an invitation to each of the group members identified in said response that have not already been invited.