Agreement problems in fault –tolerant distributed systems

Abstract

Reaching agreement in a distributed system is a fundamental issue of both theoretical and practical importance. Consensus, Atomic Commitment, Atomic Broadcast, Group Membership which are different versions of this paradigmunderly much of existing fault-tolerant distributed systems. We describe these problems, explain their relationships, and state some fundamental results on their solvability, depending on the system model. We then review and compare basic techniques to circumvent impossibility results in asynchronous systems: randomization, models of partial synchrony, unreliable failure detection.