Chapter

Parallel Computing Technologies

Volume 2127 of the series Lecture Notes in Computer Science pp 42-50

Date:

Consensus in One Communication Step

  • Francisco BrasileiroAffiliated withIRISA, Université de Rennes 1
  • , Fabíola GreveAffiliated withIRISA, Université de Rennes 1
  • , Achour MostefaouiAffiliated withIRISA, Université de Rennes 1
  • , Michel RaynalAffiliated withIRISA, Université de Rennes 1

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Abstract

This paper presents a very simple consensus protocol that converges in a single communication step in favorable circumstances. Those situations occur when “enough” processes propose the same value. (“Enough” means “at least (n - f)” where f is the maximum number of processes that can crash in a set of n processes). The protocol requires f < n/3. It is shown that this requirement is necessary. Moreover, if all the processes that propose a value do propose the same value, the protocol always terminates in one communication step. It is also shown that additional assumptions can help weaken the f < n/3 requirement to f < n/2.

Keywords

Asynchronous Distributed System Consensus Crash Failure Message Passing