A client-server oriented algorithm for virtually synchronous group membership in WANs

We describe a novel scalable group membership service designed explicitly for wide area networks. Our membership service is scalable in the number of groups supported, in the number of members in each group, and in the topology each group spans. Our service also supplies the hooks needed to provide clients with full virtual synchrony semantics. Our service attains, on average, a low message overhead by agreeing on membership within a single message round. Furthermore, our service avoids notifying the application of obsolete membership views when the network is unstable, yet it converges when the network has stabilized.