In this paper we are interested in synchronous distributed systems subject to transient and ubiquitous failures. This includes systems where failures will occur on any communication link, systems where every processor...
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In this paper we are interested in synchronous distributed systems subject to transient and ubiquitous failures. This includes systems where failures will occur on any communication link, systems where every processor will experience at one time or another send or receive failure, etc., and, following a failure, normal functioning resuming after a finite time. Notice that these cases cannot be handled by the traditional component failure models. The model we use is the communication failure model, also called the transinission failure or a dynamic faults or mobile faults model. Using this model, we study the fundamental problem of agreement in synchronous networks of arbitrary topology with ubiquitous faults. We establish bounds on the number of dynamic faults that make any non-trivial form of agreement (even strong majority) impossible;in turn, these bounds express connectivity requirements that must be met to achieve any meaningful form of agreement. We also provide, constructively, bounds on the number of dynamic faults in spite of which any non-trivial form of agreement (even unanimity) is possible. These bounds are shown to be tight for a large class of networks, which includes hypercubes, toruses, rings, and complete graphs;incidentally, we close the existing gap between possibility and impossibility of non-trivial agreement in complete graphs in the presence of dynamic Byzantine faults. None of these results is derivable in the component failure models;in particular, all our possibility results hold in situations for which those models indicate impossibility. (C) 2007 Elsevier B.V. All rights reserved.
distributed computing has been concerned with the topics of faults and failures from its very beginning (before PODC was born). The consensus problem was at the forefront of the research efforts, and an extensive body...
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ISBN:
(纸本)9798400706684
distributed computing has been concerned with the topics of faults and failures from its very beginning (before PODC was born). The consensus problem was at the forefront of the research efforts, and an extensive body of literature on the subject was developed very quickly (e.g., [5, 6, 11, 20]). The beautiful proof of the impossibility of consensus under asynchrony [7] put to rest the unsuccessful attempts to prove otherwise, and gave an even stronger impetus to the focus on synchronous *** paper Time is not a Healer [16], which we shall denote by {T¬H}, was concerned with the problem of agreement in synchronous systems where failures have mostly a transient and ubiquitous nature; that is, faults can occur anywhere in the system and, following a failure, normal functioning can resume after a finite (although unpredictable) time. These type of dynamic failures, however, could not be handled by the traditional failure models developed for the consensus and related *** the significance and novelty of the scientific and technical contributions of {T¬H}, including the model, the proof technique, and the unexpected results. Incidentally, while known for its results on omissions, {T¬H} contains also tight bounds on corruptions, additions, and the Byzantine combination of all. While known for its impossibility results, it has tight possibility results, which hold in situations for which the traditional models indicate impossibility. Over the decades, triggered by these results, an extensive literature has been developed (e.g., [3, 4, 8, 9, 13, 15, 19, 21]).The relatively recent developments in communication technology and advent of new virtual systems (e.g., wireless mobile networks, social networks) have driven the research in distributed computing to investigate problems (including consensus) in dynamic networks (e.g., [2, 10, 12]); this has inevitably brought to light the immediate connection between such networks and the ones subject to dynamic omiss
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