Synchronous Message Passing

This paper studies the characteristics of synchronous ordering of messages. Synchronous ordering of messages deenes synchronous communication based on the causality relation rather than time. We present the necessary characteristics of any algorithm providing deadlock-free synchronous ordering of the messages. We also present the suucient conditions, based on the causality relations, for any algorithm to provide synchronous ordering. The paper proposes an algorithm using acknowledgment messages to implement the suucient conditions. The acknowledgment messages are used to satisfy the causality relation between the events. The algorithm is deadlock-free, and provides a higher degree of concurrency then the algorithms which deene synchronous communication based on time.