This TS specifies the, stage three, Protocol Description of the Conference (CONF) service based on stage one and two of the ISDN CONF supplementary service. Within the Next Generation Network (NGN) the stage 3 is specified using the IP-Multimedia Call Control Protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP).
This TS specifies centralized conferencing, using a conference focus, distributed conferencing is out of scope.
This TS does not cover the cases of:
cascading conference services; and
the support of the PSTN/ISDN conference service hosted in the PSTN.