2.7.20 Centralized Conferencing (xcon)

NOTE: This charter is a snapshot of the 63rd IETF Meeting in Paris, France. It may now be out-of-date.
In addition to this official charter maintained by the IETF Secretariat, there is additional information about this working group on the Web at:

       Additional XCON Web Page

Last Modified: 2005-06-29


Adam Roach <adam@nostrum.com>
Alan Johnston <alan.johnston@mci.com>

Transport Area Director(s):

Allison Mankin <mankin@psg.com>
Jon Peterson <jon.peterson@neustar.biz>

Transport Area Advisor:

Allison Mankin <mankin@psg.com>

Mailing Lists:

General Discussion: xcon@ietf.org
To Subscribe: https://www1.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
the XCON solutions themselves will be signaling protocols, nor will
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
signaling protocols to utilize the full functionality of the XCON
architecture is outside the scope of XCON.

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:

Oct 03  Submit Requirements for Membership Manipulation for publication as Informational
Oct 03  Submit Requirements for Basic Floor Control for publication as Informational
Nov 03  Submit Conferencing Scenarios document for publication as Informational
Nov 03  Submit Use Cases for Media Topology Control for publication as Informational
Dec 03  Submit Requirements for Media Topology Control for publication as Informational
Feb 04  Submit Basic Floor Control Protocol for publication as PS
Mar 04  Submit Notification Event package extension for conference related events for publication as PS
May 04  Submit Membership Manipulation Protocol for publication as PS
Jul 04  Submit Protocol for Media Topology Control for publication


  • draft-ietf-xcon-conference-scenarios-04.txt
  • draft-ietf-xcon-floor-control-req-03.txt
  • draft-ietf-xcon-bfcp-05.txt
  • draft-ietf-xcon-framework-01.txt

    No Request For Comments

    Current Meeting Report

    IETF63 XCON Meeting
    Notes by Brian Rosen

    No agenda bash
    Revised milestones presented to be proposed to AD All SIPPING conferencing documents are complete

    Only one draft moveing what can be done?

    HS - Need some simpler generic mechanisms, limit scope
    CJ - Agree on framework, then work on mechanism

    Mary Barnes presents updates to Framework
    Several updates (2 revs since ietf62)

    Open Issues
    State and Policy Manipulation Protocol: 4 on the tables, SOAP added as a 5th
    Need more work on conference policies
    Need more explicit distinctions between templates and blueprints
    Need to align framework with SIPPING conferencing stuff

    More work to do on Floor Control and Examples

    New work items: URI schemas for identifiers, mechanisms for conference policies, possible floor control based on tempates

    HS - Can we leverage presence work on policies
    MB - Does that imply xcap
    HS - No

    Protocol choice issues:
    No clear choice based on several criteria
    RM - Can't we cross some off the list now?
    HS - Ditch Netconf (in favor of SOAP, see later)
    RM - Ditch CPCP
    CJ - SOAP is like saying ASCII
    ?? - What happened to using requirements
    MB - They all meet the requirements
    ?? - What are the names of logical entities? Functional model?
    MB - we have them
    CJ - get people to commit to review doc
    <commitments from 6 people to do this>
    RE - How about resolving open issues
    MB - Deciding protocol would help a lot, reviewers will look at policy text again

    Henning Schultzrinne presents on SOAP based protocol
    No transactions
    Map to existing data structs
    Avoid 2 level mechanism (dial out user -> get/set/delete)
    Re-use well known RPC mechanism
    Use inheritance (no templates)
    Affinity to CCCP, but further simplified

    For adding users, requests can fail partially
    CJ - Are you adding them to the dial out list (which always works) or asking them to be called right now (which might fail for some
    HS - Oh, maybe it's not an issue

    Start/stop time missing, Conference media mixing, can we do something simple now?
    RM - Cullen came up with something that works, use it
    AR - How does this work for templates at all?
    HS - schema has an extension mechanism, extend for template
    CJ - Extend the WSDL?
    HS - Yes
    ?? - What are the names of the entities? Comment, merging is hard, adding lots of users is easy
    HS - "Conference Arithmetic" is very hard. Don't think we try to do that
    CJ - Agree don't need conference arithmetic, but need to move someone from one conf to another
    RE - Need to change client/server roles to enable things like this
    GC - Need to syncronize with sipping consent framework

    Chairs: Need to have discussion on mail list and try to knock down to one.


    AR - Adam Roach
    CJ - Cullen Jennings
    GC - Gonzalo Camarillo
    HS - Henning Schulzrinne
    MB - Mary Barnes
    RE - Roni Evan
    RM - Rohan Mahy


    XCON Framework Overview & Issues
    Some XCON ideas