Clique: A toolkit for group communication using IP multicast

Widespread availability of IP multicast has renewed interest in structuring distributed applications around a group communication paradigm that exploits network-layer support for multicast applications. In the past, distributed systems that provided group communication supported a restricted group communication model. Such systems are either designed to provide reliable delivery with support for atomicity and causality or to provide simple unreliable, unordered multicast delivery. We believe that the group communication abstraction is useful to many application domains. However, the group communication requirements of an application vary widely from domain to domain. This paper describes a group communication toolkit called Clique that contains the basic building blocks required to provide a flexible group communication paradigm. Clique achieves support for a wide variety of applications by tailoring the underlying multicast mechanism to meet the application's group communications requirements with the least amount of unnecessary overhead.