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