Adaptive totally ordered multicast protocol that tolerates partitions

In this paper we present a novel algorithm that implements a totally ordered multicast primitive for a Totally Ordered Group Communication Service (TO-GCS). TO-GCS is a powerful infrastructure for building distributed fault-tolerant applications, such as totally ordered broadcast, consistent object replication, distributed shared memory, Computer Supported Cooperative Work (CSCW) applications and distributed monitoring and display applications. Our algorithm is adaptive, i.e., it is able to dynamically alter the message delivery order in response to changes in the transmission rates of the participating processes. This compensates for differences among participant transmission rates and therefore minimizes fluctuations in message delivery latency. Our algorithm is thus useful for soft real-time environments where sharp fluctuations in message delivery latency are not acceptable. Our solution provides well-defined message ordering semantics. These semantics are preserved even in the face of site and communication link failures.