CCCP originates in part as a result of experience gained from the CAR Multimedia
Conference Control system[#cmmc##1#]. The CAR system was a tightly coupled
centralised system intended for use over ISDN. As desribed earlier in
this chapter, the functionality it
provided can be summarised up by listing its basic primitives:
- Create conference
- Join/Leave Conference
- List members of conference
- Include/exclude application in conference
- Take floor
In addition, there were a number of asynchronous notification events:
- Floor change
- Participant joining/leaving
- Application included/excluded
CAR's application model was modeled around applications that could
replicate either themselves or their display onto remote machines if they
were given a list of addresses or displays, hence the include/exclude
functionality. However, these are the basic primitives required to support a
tightly coupled conference, although for some uses others may be added.
Any conference control system that claims to be fairly generic must be able
to support these primitives with reasonable reliability. (Absolute
consistency is not really a feasible option in a multiway conference)
Loosely coupled conferences put less constrains on the protocols used, but
must scale to much larger numbers, and must be very tolerant of loss and
network segmentation.
Taking the modular approach described above, we would expect to change
conference controllers when moving from one regime to another, but we do not
wish to change the media applications too.