Efficacy of Floor Control Protocols in Distributed Multimedia Collaboration

摘要

Distributed multipoint applications for group interaction across wide-area networks, such as for simulation and telecollaboration, are becoming increasingly popular. While reliable multicasting has made significant advances in recent years, effective mechanisms to synchronize and coordinate work within large multicast groups and across long distances are still lacking. Synchronous sharing of resources, whose operational semantics prohibit parallel usage, typically creates race conditions among users, which can be resolved through an access discipline called floor control. Existing solutions on floor control, implemented either at the session or application layer, are mostly proprietary, limited in scope, and not scalable. Furthermore, no performance comparison of floor control protocols has been attempted to date. The authors present a novel taxonomy and comparative performance analysis of known classes of floor control protocols, ranging from socially mediated control to protocols operating on ring and tree topologies. They find that aggregation and selective transmission of control information in a tree structure is the most promising solution with regard to scalability, efficacy, and robustness. The principal operation of such a tree protocol is outlined, which dynamically organizes participants in a multi-level control tree and aggregates resource sharing directives on the paths between interacting stations.