Centralized Conferencing
The IETF has a new working group called the Centralized Conferencing Work-
ing Group, or XCON [9] that is extending the SIP conferencing work in the SIP
and SIPPING working groups. The work is limited to conferences that have a
focus—a centralized point of signaling, admission, and authentication. The
media can still be full mesh, distributed, or even multicast, but the signaling
must be centralized.
So far, the working group has produced a framework and data model docu-
ment [10]. The actual protocols used to implement the framework are still
under discussion. The working group has also published a floor control proto-
col known as Binary Floor Control Protocol (BFCP) [11].
Summary
This chapter has introduced a number of models of SIP conferencing such as
endpoint mixing, SIP server and distributed media, dial-in conferences, ad
hoc, centralized, and large scale multicast conferences. We have also shown
how SIP can support changes in the nature of conference services. Protocols for
advanced conferencing services are being developed in the IETF Centralized
Conferencing (XCON) working group.
References
[1] “The Internet Multimedia Conferencing Architecture” by M. Handley, J.
Crowcroft, and C. Borman. Internet Draft, IETF, July 2000.
[2] “Session Initiation Protocol (SIP)-H.323” by H. Schulzrinne and C. Agboh.
Interworking Requirements, RFC 4123, July 2005.
[3] “A Framework for Conferencing with the Session Initiation Protocol” by J.
Rosenberg. RFC 4353, IETF, February 2006.
[4] “High-Level Requirements for Tightly Coupled SIP Conferencing” by O.
Levin and R. Even. IETF RFC 4245, November 2005.
[5] “Session Initiation Protocol Call Control - Conferencing for User Agents”
by A. Johnston and O. Levin. IETF Internet Draft, June 2005, work in
progress.
[6] “Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)”
by J. Rosenberg, H. Schulzrinne, and P. Kizivat RFC 3840, August 2004.
[7] “A Session Initiation Protocol (SIP) Event Package for Conference State” by
J. Rosenberg, H. Schulzrinne, and O. Levin.” IETF Internet Draft, July 2005,
work in progress.
SIP Conferencing 251