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It should be clear that not all conferences need an explicit conference control system, and not all conferences need to utilise the services provided by the CMMC. If video, audio and shared workspace are all provided in an entirely distributed fashion (as with the LBL whiteboard and IVS), no additional conference control system is required, since membership and participation are handled by the multicast group mechanism of the Mbone. If, however, any of the additional video, audio or shared workspace functionality outlined above are required, then some additional form of explicit conference control is required.
The original conference control system for the MICE CMMC was to be based on the CAR Conference Control system from UCL. The basic conference control functions were:
This functionality is provided by a centralised Conference Server, remote Conference Management Applications, and a number of applications that communicate with the conference server using remote procedure calls from the CAR library.
Problems with running such a tightly coupled system over unreliable networks mean that we are currently working to substitute a more distributed and fault tolerant conference control model known as the Conference Communication Channel Protocol (CCCP). A specification of CCCP is under development in Jan 1994, and so cannot be included in this version of this document. However, from the point of view of the Channel Server module, the interface to conference control will not change, and is specified later as MIC-0. CCCP will also provide additional facilities which will aid the control and interworking of distributed multicast applications, and so will also be applicable to conferences that do not employ the CMMC.
This basic conference control functionality of both CAR and CCCP provides the information for applications to locate the remote machines for running clients, and a simple floor control scheme for those applications that require it. It also provides information for video and audio servers to:
It should be stressed that the conference control system itself does not provide these resource allocation functions; this is handled by the resource allocation part of the CMMC. This split of functionality keeps the conference control system minimalist, so that it can also be used outside of the CMMC when resource allocation is not required. The Conference Control system and the Booking and Resource Allocation systems are shown in figure 9.
Version 2.0