Scaling from tightly coupled to loosely coupled conferences

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: In addition, there were a number of asynchronous notification events: 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.