A novel group coordination protocol for collaborative multimedia systems

Group collaboration in distributed multimedia environments extends gradually to larger groups and wide area networks. While reliable multicasting has made significant advancements in recent years, effective mechanisms to synchronize and coordinate work within large multicast groups and across long distances are still lacking. Group coordination is here understood as the mediated access to shared remote resources in synchronous groupwork, as for example in telecollaboration and distributed simulation environments, complementing protocols for group membership, media synchronization and reliable ordered multicast. A comparative analytic model for known classes of group coordination mechanisms, ranging from socially mediated control to floor control in ring and tree topologies, is presented. It is shown that hierarchical group coordination is the most efficient and scalable approach to date. Based on these findings, a novel protocol is described, which dynamically organizes participants in a multilevel control tree and aggregates resource sharing directives on the paths between interacting stations