A multicast group communication protocol, engine, and bridge for CORBA

Multicast group communication is needed for fault-tolerant distributed syst ems and, in particular, for the new Fault Tolerant CORBA standard, to maint ain strong replica consistency. However, different multicast group communic ation protocols are appropriate for different environments, which makes it difficult to define a single standard multicast protocol. In this paper, we present a multicast group communication engine and bridge for CORBA that a llows multiple group communication protocols to be used concurrently, We al so present the Fault Tolerant Multicast Protocol, a group communication pro tocol that allows different fault tolerance systems to interoperate. The group communication engine and bridge places Lamport timestamps on mess ages, and multicasts messages to groups, using one or more group communicat ion protocols. The group communication protocols reliably deliver the times tamped messages in timestamp order to the group communication engine, which integrates these streams of messages into a single stream for delivery in timestamp order. The Fault Tolerant Multicast Protocol operates over IP Mul ticast, and consists of the Reliable Multicast Protocol which provides reli able source-ordered message delivery, the Reliable Ordered Multicast Protoc ol which provides reliable totally ordered message delivery, and the Host G roup Membership Protocol which provides host group membership services. Cop yright (C) 2001 John Wiley & Sons, Ltd.