Analysis of multipoint videoconferencing under reroutable route-configuration assignment

We study the use of reroutable assignment for multipoint video conferences in a high-speed network. A conference model is constructed and conference calls are classified. A conference of a particular type can ride on different route-configurations. According to the location of the current speaker, a conference has different modes of operation. Two network management functions are discussed: call admission ensures a preset QOS requirement by blocking new calls that causes congestion; route-configuration assignment determines the multicast tree for distributing the video of the current speaker. The reroutable route-configuration assignment is introduced. It allows a change of route-configuration when there is a change of speaker. Two reroutable assignment schemes are studied. In the normal scheme, a conference is always rerouted to the least congested route-configuration; while in the sticky scheme, a conference is only rerouted when the current route-configuration is congested. The video freeze probability, rerouting probability and the extended capacity space are derived. An example shows that the video freeze probabilities of the two schemes do not differ significantly. The sticky scheme, however, is superior as it gives a much smaller rerouting probability than the normal scheme