Department of Computer Science & Engineering

We describe a novel scalable group membership algorithm designed for wide area networks (WANs). Our membership service does not evolve from existing LAN-oriented membership services; it was designed explicitly for WANs. Our algorithm provides agreement on membership in a single message round in most cases, yielding a low message overhead. It avoids flooding the network and uses a scalable failure detection service designed for WANs. Furthermore, our algorithm avoids notifying the application of obsolete membership views when the network is unstable, and yet it converges when the network stabilizes. In contrast to most group membership services, we separate membership maintenance from reliable communication in multicast groups: membership is not maintained by every process, but only by dedicated servers. The membership servers are not involved in the communication among the members of the groups. This design makes our membership service scalable in the number of groups supported, in the number of members in each group, and in the topology spanned by each group. Our service is complemented by a virtually synchronous communication service which provides clients with full virtual synchrony semantics.

Pre-2018 CSE ID: CS1999-0623