This paper suggests that a distributed system should support two communication paradigms: Remote Procedure Call (RPC) and group commumcation. The former is used for point-to-point communication; the latter is used for one-to-many communication. We demonstrate that group communication is an important paradigm by showing that a fault-tolerant directory service is much easier to implement with groups than with RPC and is also more efficient. The directory service exemplifies distributed services that provide high reliability and availability by replicating data.
M. Frans Kaashoek, Andrew S. Tanenbaum, Kees Verst