Solving the consensus problem in a mobile environment

Abstract

Atomic broadcast or non-blocking atomic commitment are classic agreement problems encountered when designing fault-tolerant distributed systems. Specific protocols that solve such agreement problems can be designed based on a common building block, namely the consensus service. Unfortunately, the consensus problem has no deterministic solution in an asynchronous distributed system that is subject to even a single process crash failure. Among the solutions proposed to circumvent this impossibility result, the concept of unreliable failure detectors proposed by Chandra and Toueg is particularly attractive. They have defined a protocol that solves the consensus problem when the assumption that the underlying failure detector belongs to the class /spl square/S holds true. This paper presents an extension of their protocol that allows to solve this fundamental problem in a mobile environment. In such an environment, the problem is more challenging: based on their initial states, a set of mobile hosts must agree on a common decision, despite disconnections, changes of location and failures of mobile/fixed hosts.