2.5.14 Centralized Conferencing (xcon)

NOTE: This charter is a snapshot of the 75th IETF Meeting in Stockholm, Sweden. It may now be out-of-date.

Last Modified: 2009-10-20


Alan Johnston <alan@sipstation.com>
Richard Barnes <rbarnes@bbn.com>

Real-time Applications and Infrastructure Area Director(s):

Robert Sparks <rjsparks@nostrum.com>
Cullen Jennings <fluffy@cisco.com>

* The Real-time Applications and Infrastructure Area Directors were seated during the IETF 65.

Real-time Applications and Infrastructure Area Advisor:

Robert Sparks <rjsparks@nostrum.com>

Mailing Lists:

General Discussion: xcon@ietf.org
To Subscribe: https://www.ietf.org/mailman/listinfo/xcon
Archive: http://www.ietf.org/mail-archive/web/xcon/index.html

Description of Working Group:

The focus of this working group is to develop a standardized suite of
protocols for tightly-coupled multimedia conferences, where strong
security and authorization requirements are integral to the solution.
Tightly-coupled conferences have a central point of control and
authorization (known as a focus) so they can enforce specific media and
membership relationships, and provide an accurate roster of
participants. The media mixing or combining function of a tightly-
coupled conference need not be performed centrally, however.

The scope of this effort is intentionally more narrow than previous
attempts to standardize conferencing (e.g. centralized control), and is
intended to enable interoperability in a commercial environment which
already has a number of non-standard implementations using some of the

Privacy, security, and authorization mechanisms are integral to the
solution generated by the working group. This includes allowing
participants to be invisible to all but the conference owner, or to be
visible but participate anonymously with respect to some or all of
the other participants.

Authorization rules allow for participants and non-participants
to have roles (ex: speaker, moderator, owner), and to be otherwise
authorized to perform membership and media manipulation for or on
behalf of other participants. In order to preserve these properties,
the protocols used will require implementation of channel security
and authentication services.

Due to the centralized architecture of the WG, XCON's mechanisms will
place requirements on the signaling protocol used between the focus
and the participants. At a high level, the signaling protocol must be
able to establish, tear down, modify, and perform call control
operations on multimedia streams, including voice, video, and instant
messaging, in both a centralized and distributed mixing architecture.
SIP will be the reference session signaling protocol used for examples;
however, none of the XCON solutions themselves will be signaling
protocols, nor will XCON extend existing signaling protocols. Other
signaling protocols than SIP may be used between the focus and
participants, including non-IETF protocols, but the requirements and
possible extensions needed for other signaling protocols to utilize the
full functionality of the XCON architecture is outside the scope of

The deliverables for the group will be:
- A mechanism for membership and authorization control
- A mechanism to manipulate and describe media "mixing" or "topology"
  for multiple media types (audio, video, text)
- A mechanism for notification of conference related events/changes
  (for example a floor change)
- A basic floor control protocol

The initial set of protocols will be developed for use in unicast media
conferences. The working group will perform a second round of work to
enhance the set of protocols as necessary for use with multicast media
after their initial publication.

The following items are specifically out-of-scope:
- Voting
- Fully distributed conferences
- Loosely-coupled conferences (no central point of control)
- Far-end device control
- Protocol used between the conference controller and the mixer(s)
- Capabilities negotiation of the mixer(s)
- Master-slave cascaded conferences

The working group will coordinate closely with the SIPPING and
MMUSIC working groups. In addition the working group will cooperate
with other groups as needed, including SIP, MSEC, AVT, and the W3C
SMIL working groups. In addition, the working group will consider
a number of existing drafts as input to the working group.

Goals and Milestones:

Done  Submit Requirements for Basic Floor Control for publication as Informational
Done  Submit Conferencing Scenarios document for publication as Informational
Done  Submit Basic Floor Control Protocol for publication as PS
Done  Submit Framework for publication as PS
Done  Submit Event Notification Package for publication as PS
Aug 2009  Submit Conference Data Model for publication as PS
Aug 2009  Submit Conference Control Protocol for publication as PS
Dec 2009  Submit Policy Model for publication as PS
Dec 2009  Set milestones for any IM-related conferencing work
Apr 2010  Submit Conferencing Call Flows Document for publication as Informational


  • draft-ietf-xcon-event-package-01.txt
  • draft-ietf-xcon-ccmp-03.txt
  • draft-ietf-xcon-examples-01.txt

    Request For Comments:

    RFC4376 I Requirements for Floor Control Protocol
    RFC4582 PS The Binary Floor Control Protocol (BFCP)
    RFC4597 I Conferencing Scenarios
    RFC5018 PS Connection Establishment in the Binary Floor Control Protocol (BFCP)
    RFC5239 PS A Framework for Centralized Conferencing

    Meeting Minutes


    Agenda Slides
    CCMP Call Flow Examples