<title>Dynamic reconfiguration in tightly coupled conference environments</title>

Abstract

The communication and cooperation of widely distributed applications is enabled by conference control services for tightlycoupled environments like SCCS (Scalable Conferencing Control Service) providing a tight control of resources for application state synchronization and multipoint communication in the conference. A major issue in the design of such services is the scalability in terms of users and distribution. Especially the used resource management scheme is crucial for a high scalability. SCCS uses an own-developed scheme which improves the response time of resource requests especially if they are local in the topology. For further improvement of that scheme the reconfiguration of existing topologies is another issue. The problem of performing a reconfiguration (without blocking the conference) is not within the scope of this paper. The scope is the need for a dynamic decision how and if the conference should be reconfigured. For that a scheme is presented which detects active entities in the conference and groups them closer to each other in the topology to improve further requests. A definition of 'activity' is given together with a scheme to identify that activity during a running conference. For that, unique sets of active entities in the running conference are determined built according to the used resources in the sets. We present a placement algorithm for those active entity sets to optimize further resource requests for the specific resources used by the corresponding entity set. A scheme is presented which is the basis for the decision to perform a reconfiguration and it is embedded in the conferencing service SccS. Additionally a performance evaluation is presented using an automata-based load model to determine the performance gain in different scenarios.