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Atomic Broadcast: From Simple Message Diffusion to Byzantine Agreement
 Information and Computation
, 1985
"... In distributed systems subject to random communication delays and component failures, atomic broadcast can be used to implement the abstraction of synchronous replicated storage, a distributed storage that displays the same contents at every correct processor as of any clock time. This paper present ..."
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Cited by 217 (15 self)
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In distributed systems subject to random communication delays and component failures, atomic broadcast can be used to implement the abstraction of synchronous replicated storage, a distributed storage that displays the same contents at every correct processor as of any clock time. This paper presents a systematic derivation of a family of atomic broadcast protocols that are tolerant of increasingly general failure classes: omission failures, timing failures, and authenticationdetectable Byzantine failures. The protocols work for arbitrary pointtopoint network topologies, and can tolerate any number of link and process failures up to network partitioning. After proving their correctness, we also prove two lower bounds that show that the protocols provide in many cases the best possible termination times. Keywords and phrases: Atomic Broadcast, Byzantine Agreement, Computer Network, Correctnesss, Distributed System, Failure Classification, FaultTolerance, Lower Bound, RealTime Syste...
Parametric realtime reasoning
 IN PROCEEDINGS OF THE 25TH ANNUAL SYMPOSIUM ON THEORY OF COMPUTING
, 1993
"... Traditional approaches to the algorithmic verification of realtime systems are limited to checking program correctness with respect to concrete timing properties (e.g., "message delivery within 10 milliseconds"). We address the more realistic and more ambitious problem of deriving symbolic constrai ..."
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Cited by 95 (6 self)
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Traditional approaches to the algorithmic verification of realtime systems are limited to checking program correctness with respect to concrete timing properties (e.g., "message delivery within 10 milliseconds"). We address the more realistic and more ambitious problem of deriving symbolic constraints on the timing properties required of realtime systems (e.g., "message delivery within the time it takes to execute two assignment statements"). To model this problem, we introduce parametric timed automata  finitestate machines whose transitions are constrained with parametric timing requirements. The emptiness question for parametric timed automata is central to the verification problem. On the negative side, we show that in general this question is undecidable. On the positive side, we provide algorithms for checking the emptiness of restricted classes of parametric timed automata. The practical relevance of these classes is illustrated with several verification examples. There remains a gap between the automata classes for which we know that emptiness is decidable and undecidable, respectively, and this gap is related to various hard and open problems of logic and automata theory.
Consensus in the Presence of Timing Uncertainty: Omission and Byzantine Failures
 In Proceedings 10th ACM Symposium on Principles of Distributed Computing
, 1991
"... We consider the time complexity of reaching agreement in a semisynchronous model of distributed systems, in the presence of omission and Byzantine failures. In our semisynchronous model, processes have inexact knowledge about the time to perform certain primitive actions: messages arrive within ti ..."
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Cited by 13 (1 self)
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We consider the time complexity of reaching agreement in a semisynchronous model of distributed systems, in the presence of omission and Byzantine failures. In our semisynchronous model, processes have inexact knowledge about the time to perform certain primitive actions: messages arrive within time d of when they are sent and the time between two consecutive steps of any process is in the known interval [c 1 ; c 2 ]. We use C = c 2 =c 1 as a measure of the timing uncertainty. A simple adaptation of the synchronous lower bound shows that at least time (f + 1)d is required to tolerate f failures; time (f + 1)Cd is sufficient for stopping or omission failures by directly simulating synchronous rounds. By strengthening the algorithm for stopping failures of Attiya, Dwork, Lynch, and Stockmeyer ([1]), we derive an algorithm for omission failures that has minimal dependency on the uncertainty factor C. If fewer than half the processes are faulty then the running time is 4(f + 1)d + Cd, wh...
Time Bounds for Decision Problems in the Presence of Timing Uncertainty and Failures
 Journal of Parallel and Distributed Computing
, 1993
"... This paper studies the time complexity of solving decision problems in ..."
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Cited by 10 (1 self)
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This paper studies the time complexity of solving decision problems in
Efficiency of Partial Synchrony, and Resource Allocation in Distributed Systems.
, 1994
"... This dissertation is in two parts, covering two distinct areas of distributed computing. The first part concerns timing models in distributed systems that lie between the synchronous and asynchronous models in terms of their assumption on synchrony. We study their time complexity for solving distrib ..."
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Cited by 7 (4 self)
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This dissertation is in two parts, covering two distinct areas of distributed computing. The first part concerns timing models in distributed systems that lie between the synchronous and asynchronous models in terms of their assumption on synchrony. We study their time complexity for solving distributed computing problems in shared memory (SM) and messagepassing (MP) systems. We consider four timing parameters: the upper and lower bounds on process step time and message delay. Timing models are obtained by considering independently whether each parameter is known (i.e., is hardwired into processes' code) or unknown, giving rise to four SM models and 16 MP models. We also study other timing models that are not covered by this framework. We show a general time complexity hierarchy indicating inherent time complexity gaps among the models. The time complexity gaps are introduced by the time complexity of the session problem, an abstraction of fundamental synchronization problems in dist...