Skip to Main Content
Communication among multiple peer processes is referred to as group communication. In this paper we discuss a hierarchical group of processes to reduce communication and computation overheads, which is composed of disjointed subgroups. Each subgroup has gateway processes which communicate with other subgroups. Even if messages are causally ordered in a subgroup, the messages may not be causally ordered in another subgroup. We discuss how causality of messages among every pair of processes in a subgroup is related with causalities of the messages in another subgroups. In addition, we present a protocol to causally deliver messages through subgroups hierarchically structured.