Rapporteur: Mr. Kreipl, Michael Antecedent:
This TS specifies the stage three Protocol Description of the Closed User Group (CUG) service, based on stage one and two of the ISDN Communication diversion supplementary services. It provides the protocol details in the IP Multimedia (IM) Core Network (CN) subsystem based on the Session Initiation Protocol (SIP) and the Session Description Protocol (SDP).
The CUG service enables users to form groups of members, whose communication profile is restricted for incoming and outgoing communications.
Members of a specific CUG can communicate among themselves but not, in general, with users outside the group.
Specific CUG members can have additional capabilities that allow them to initiate outgoing communications to users
outside the group, and/or to accept incoming communications from users outside the group. Specific CUG members can
have additional restrictions that prevent outgoing communications to other members of the CUG, or prevent incoming
communications from other members of the CUG.
A closed user group consists of a number of members from one or more public, and/or private networks. A specific user
may be a member of one or more CUGs. Subscription to a closed user group shall be defined for all communication
services, or in relation to one, or to a list of communication services.