Voting without version numbers

Abstract

Voting protocols are widely used to provide mutual exclusion in distributed systems and to guarantee the consistency of replicated data in the presence of network partitions. Unfortunately, the most efficient voting protocols require fairly complex metadata to assert which replicas are up-to-date and to denote the replicas that belong to that set. We present a much simpler technique that does not require version numbers and maintains only n+log(n) bits of state per replica. We show, under standard Markovian assumptions, that a static voting protocol using our method provides nearly the same data availability as a static voting protocol using version numbers. We also describe a dynamic voting protocol using our method that provides the same data availability as a dynamic voting protocol using much more complex metadata.