Unbeatable Consensus
نویسندگان
چکیده
The unbeatability of a consensus protocol, introduced by Halpern, Moses and Waarts in [14],is a stronger notion of optimality than the accepted notion of early stopping protocols. Usinga novel knowledge-based analysis, this paper derives the first practical unbeatable consensusprotocols in the literature, for the standard synchronous message-passing model with crashfailures. These protocols strictly dominate the best known protocols for uniform and for non-uniform consensus, in some case beating them by a large margin. The analysis provides a newunderstanding of the logical structure of consensus, and of the distinction between uniform andnonuniform consensus. Finally, the first (early stopping and) unbeatable protocol that treatsdecision values “fairly” is presented. All of these protocols have very concise descriptions, andare shown to be efficiently implementable.
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