Ulrich Schmid

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We present a new fault-tolerant intersection function ${\boldmath{\cal F}}$ , which satisfies the Lipschitz condition for the uniform metric and is optimal among all functions with this property. ${\boldmath{\cal F}}$ thus settles Lamport's question about such a function raised in [5]. Our comprehensive analysis reveals that ${\boldmath{\cal F}}$ has(More)
We provide a suite of impossibility results and lower bounds for the required number of processes and rounds for synchronous consensus under transient link failures. Our results show that consensus can be solved even in presence of O(n) moving omission and/or arbitrary link failures per round, provided that both the number of affected outgoing and incoming(More)
In this paper, we develop and analyze a simple interval-based algorithm suitable for fault-tolerant external clock synchronization. Unlike usual internal synchronization approaches, our convergence function-based algorithm provides approximately synchronized clocks maintaining both precision and accuracy w.r.t. external time. This is accomplished by means(More)
This paper introduces a simple fault-tolerant tick generation algorithm based on Srikanth & Toueg's consistent broadcast primitive that can be directly implemented in VLSI using asynchronous digital logic. The need for adaption originates from two peculiarities of hardware implementations: (i) Fine-grained parallel asynchronous computations, which(More)
This paper shows that deterministic consensus in synchronous distributed systems with link faults is possible, despite the impossibility result of (Gray, 1978). Instead of using randomization, we overcome this impossibility by moderately restricting the inconsistency that link faults may cause system-wide. Relying upon a novel hybrid fault model that(More)
It has long been known that the consensus problem cannot be solved deterministically in completely asynchronous distributed systems, i.e., systems (1) without assumptions on communication delays and relative speed of processes and (2) without access to real-time clocks. In this paper, we define a new asynchronous system model. Instead of assuming reliable(More)
We present a novel partially synchronous system model, which augments the asynchronous model by a (possibly unknown) bound Θ on the ratio of longest and shortest end-to-end delays of messages simultaneously in transit. An upper bound on those delays need not exist, however, and even Θ may hold only after some unknown global stabilization time. Θ-algorithms(More)