Transition within sip based multi-party communication: From tightly-coupled to fully-coupled conference

Many models and topologies have been proposed for multi-party internet conferencing. The end-system mixing topology, where nodes are loosely coupled, is considered as one of the most popular, easy to deploy and less expensive among the other topologies. Otherwise, in some context, the centralized topology presents some drawbacks that limit conference development particularly when focus user (mixer) has to leave conference or for other cases where participant number becomes too high to be correctly mixed. On the other hand, the fully-coupled conference model spreads the mixing load between participants and enables them to leave the conference without preventing remaining participants to continue conferencing. Enabling transition to fully-coupled model should resolve tightly coupled limitations. This work explains how to enable such a transition between the two models using SIP protocol primitives. Two approaches to enable model transition are explored and their performance is evaluated.