Subject: [RAI] Distributed Conferencing BOF

From: Cullen Jennings <[email-masked]>
Date: Wed, 21 Sep 2011 09:37:01 -0600

Simon has proposed a Distributed Conferencing WG in the charter below. This work was discussed long ago in XCON and the decision was to wait till the XCON work was further along. Now that the XCON works is wrapping up, we should consider taking on this new work. 

The ADs and chairs discussed using dispatch agenda time for this and our initial take was that this was a pretty big chunk of work that could involve input from people outside the usual Dispatch participants. Because of that, we think this would probably best be done as a full BOF. If people don't think this is the right path forward for this work, we welcome feedback and reconsider what to do. The current plan is to propose this a normal IETF BOF at the upcoming IETF. Of course we would want to encourage discussion of this charter ahead of time. Given the tentative plan to run this as a BOF, I have added the RAI mailing list to this thread. 

Thanks,
Cullen

- Description of Working Group

The focus of this Working Group is to develop a standard solution for scalable conferencing over the Internet. The WG will define a standard suite of protocols for distributed conferencing and will draw inspiration from the work carried out in the XCON working group, which has defined a complete architecture for centralized conferencing.  DCON is based on the idea that a
distributed conference can be setup by appropriately orchestrating the operation of a number of XCON focus elements, each in charge of managing a certain number of participants. Interaction between each participant and the corresponding conference focus will be entirely based on the standard XCON framework, whereas inter-focus interaction will be defined by this WG.

In the DCON architecture a number of entities are used to manage conference setup in the presence of clients which are distributed across a geographical
network.  Each managing entity plays the role of a conference focus as defined in the XCON working group documents. Indeed, each XCON focus will be in charge of managing a certain number of clients falling under its own "realm".  In order to move the XCON scope towards a distributed environment, we will introduce inter-focus coordination, which is needed to effectively setup and manage conference instantiation and coordination.  As in the centralized    case, we will define logical entities and naming conventions.  An appropriate data model for distributed conferencing will be potentially defined and will extend, when needed, the XCON data model.  Furthermore, we will propose the adoption of a suitable set of protocols which are complementary to the call signaling protocols and are needed to support advanced conferencing applications.

The WG will basically need to introduce two major functions: (i) a coordination level among conference focus entities; (ii) a way to effectively distribute conference state information.  As to the first point above, the coordination level is needed in order to manage a distributed conference along its entire life-cycle. For instance, once a user decides to create a new conference, the corresponding conference focus has to distribute conference information to all other foci, in such a way as to enable other potential participants to retrieve the needed data and possibly subscribe to the event. The WG will make the assumption that all the operations needed inside a single conference cloud are   managed via the protocols and interfaces defined inside the XCON working group.  Hence, each single cloud will keep on being based on a star-topology graph for all what concerns the call signaling part. The various available stars will then be connected through an upper-layer topology providing inter-focus communication.  The overall topology of the distributed conferencing scenario will look like an overlay network of focus entities, each managing an underlying "centralized" conferencing island. The WG will envisage the possibility to exploit extended Instant Messaging (IM) protocols (e.g. XMPP) for inter-focus communication.
As to the second point mentioned above, it looks clear that a way to propagate information about conferences is needed when switching the view from a centralized to a distributed perspective.  Indeed, whenever a new conference is created (or an active conference changes its state) such an event has to be communicated to all interested (or active) participants.  Given the intrinsic nature of the distributed framework (which actually expands the centralized one through the introduction of an overlay network of focus entities), the actual   flow of information will always foresee the interaction among conference focus entities for both conference information exchanging and state changes notifications.  The same obviously applies also to the involved natively centralized protocols defined in the XCON framework.  A suitable mechanism will be defined by the WG, allowing for the dispatching of such centralized messages across the DCON network. The mechanism in question must be fully compliant with the existing operation of XCON clouds, which must keep their local participants   totally unaware of the potential distributed nature of conferences. Conference state propagation will take place in a number of alternative ways.  For instance, each focus might flood the received information across an inter-focus communication mesh, thus guaranteeing that potential participants belonging to heterogeneous islands can be reached.  In such case, focus entities are "stateful", i.e. each of them stores information about current sessions and forwards such information to all peering entities in order to get them up-to-date with respect to available conference sessions. 
On the other hand, a distributed repository might be employed for the sake of storing conference information.  Focus entities would access such repository, both to publish (either upon creation of a new conference, or to notify a change in the state of an active conference) and to retrieve information about active conferences (e.g. when a new participant wants to access the list of ongoing/scheduled conference sessions he might be interested to join).  In this last case, focus entities are "stateless". Finally, the WG will evaluate the benefits deriving from the adoption of a pure peer-to-peer approach for the purpose of conference state information spreading.

The deliverables for the group will be:

- A Framework for Distributed Conferencing (backward-compatible with XCON in the single-cloud case)
- A survey of potential solutions to the construction and maintenance of a DCON conference repository (stateless, stateful, based on flooding, p2p, etc.)
- Requirements for an XCON-DCON Synchronization Protocol (XDSP)
- Specification of the XDSP
- DCON call-flows draft (involving the use of XDSP)

- Goals and Milestones

February 2012 --> Submit Framework document for publication as PS
April 2012 --> Submit XDSP Requirements document for publication as Informational
June 2012 --> Submit survey of solutions for the DCON conference repository for publication as Informational
September 2012 --> Submit XDSP Specification document for publication as PS
January 2013 --> Submit DCON call flows draft for publication as Informational