Scalable group membership services for novel applications

Group communication is a useful abstraction in the development of highly available distributed and communication-oriented applications in wide area networks (WANs). The most important aspects of this abstraction are the dynamic maintenance of group membership and its diverse semantics for interleaving membership change notiications within the ow of regular messages. In this paper we propose a new architecture for a scalable group membership service for wide area environments. Our architecture provides two diierent service levels and their semantics, each geared to diierent applications with diierent needs: The congress membership service which provides simple semantics of membership approximation, and the moshe service, which extends congress, provides full virtual synchrony semantics. The novelty of our design is in its client-server approach, which allows lightweight clients to beneet from advanced membership services. Furthermore , our design supports the coexistence of full-edged clients along with thin clients.