The present document 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).
The present document specifies centralized conferencing, using a conference focus, distributed conferencing is out of
scope.
The present document does not cover the cases of :
a) cascading conference services; and
b) the support of the PSTN/ISDN conference service hosted in the PSTN.