The power and limit of adding synchronization messages for synchronous agreement

Jiannong Cao, Michel Raynal, Xianbing Wang, Weigang Wu

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


This paper investigates the use of additional synchronization messages in round-based message-passing synchronous systems. It first presents a synchronous computation model allowing a process to send such messages. The difference with respect to the traditional round-based synchronous model lies in the sending phase, where a process can first send a data message to each other process, and then, without a break, a synchronization message (their sendings can be pipelined). This model is suited to the class of local area networks where communication channels are reliable. (It is not for networks where unreliable communication requires message retransmission.) To illustrate the model, the paper presents a uniform consensus algorithm suited to this model. This algorithm, based on the rotating coordinator paradigm, allows the processes to decide in at most f + 1 rounds where f is the actual number of processes that crash in the corresponding run. (This improves the f + 2 lower bound of the traditional synchronous model.) In addition to its efficiency, the algorithm enjoys another first class property, namely, design simplicity. The paper focuses also on lower bound results, and shows that any uniform consensus algorithm designed for the proposed model, requires at least f + 1 rounds in the worst case. The proposed algorithm is consequently optimal. In that sense the paper has to be seen as an investigation of both the power and the limit of adding synchronization messages to synchronous systems built on top of local networks with reliable communication.
Original languageEnglish
Title of host publicationICPP 2006
Subtitle of host publicationProceedings of the 2006 International Conference on Parallel Processing
Number of pages8
Publication statusPublished - 1 Dec 2006
EventICPP 2006: 2006 International Conference on Parallel Processing - Columbus, OH, United States
Duration: 14 Aug 200618 Aug 2006


ConferenceICPP 2006: 2006 International Conference on Parallel Processing
Country/TerritoryUnited States
CityColumbus, OH


  • Distributed system
  • Early-stopping
  • Lower bound
  • Message-passing
  • Round-based computation
  • Synchronous system
  • Two-step
  • Uniform consensus

ASJC Scopus subject areas

  • Hardware and Architecture
  • Engineering(all)


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