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Centralized Conferencing

Document Charter Centralized Conferencing WG (xcon)
Title Centralized Conferencing
Last updated 2011-09-26
State Approved
WG State Concluded
IESG Responsible AD Robert Sparks
Charter edit AD (None)
Send notices to (None)

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.