Liveness in Timed and Untimed Systems

AbstractWhen proving the correctness of algorithms in distributed systems, one generally considerssafetyconditions andlivenessconditions. The Input/Output (I/O) automaton model and its timed version have been used successfully, but have focused on safety conditions and on a restricted form of liveness called fairness. In this paper we develop a new I/O automaton model, and a new timed I/O automaton model, that permit the verification of general liveness properties on the basis of existing verification techniques. Our models include a notion ofreceptivenesswhich extends the idea ofreceptivenessof other existing formalisms, and enables the use of compositional verification techniques. The presentation includes anembeddingof the untimed model into the timed model which preserves all the interesting attributes of the untimed model. Thus, our models constitute acoordinated frameworkfor the description of concurrent and distributed systems satisfying general liveness properties

Admission control and routing : theory and practice

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 183-190).by Rainer Gawlick.Ph.D

Concurrent Timestamping Made Simple

Concurrent Timestamp Systems (CTSS) allow processes to temporally order concurrent events in an asynchronous shared memory system. Bounded memory constructions of a CTSS are extremely powerful tools for concurrency control, and are the basis for solutions to many coordination problems including mutual exclusion, randomized consensus, and multiwriter multireader atomic registers

Competitive On-line Selective Multicast via Dense Trees Construction (Extended Abstract)

) Baruch Awerbuch 1;2 Yossi Azar 3 Rainer Gawlick 2 1 Johns Hopkins University 2 Laboratory for Computer Science, MIT 3 Tel-Aviv University May 3, 1994 Abstract This paper introduces the problem of selective online multicast and presents an log O(1) n thruput competitive solution, which handles issues of route selection and admission control, in general networks with n nodes. For each node and each multi-cast (broadcast) group, we assume that the node has an arbitrary probability with which it wishes to join the group. 1 Introduction Motivation. The introduction of fiber technology gives rise to new applications, such as interactive TV and video-conferencing, that feature multi-point communication. Applications with multi-point communication can be modeled as sources that broadcast information to subscribing nodes along a spanning (Steiner) tree. In modern networks, (e.g., ATM networks [deP91, Bou92], high-speed networks [ACG + 90, CG88, ACG91, CGG91], or private vi..

Maximal Dense Trees and Competitive On-line Selective Multicast (Extended Abstract)

) Baruch Awerbuch 1;2 Yossi Azar 3 Rainer Gawlick 2 1 Johns Hopkins University 2 Laboratory for Computer Science, MIT 3 Tel-Aviv University Abstract In this paper we introduce the problem of selective multi-cast and develop the first on-line algorithm for general networks with provable performance guarantees. The essence of the problem is to maximize the number of accommodated users, in presence of bounded network resources. Our algorithm exhibits a poly-logarithmic competitive ratio in terms of the number of accepted users. The techniques and concepts used to develop the algorithm seem of interest in their own right. In particular, the new graph-theoretic concept of maximal dense subsets, introduced in this paper, motivated the first efficient approximation for the k-MST problem. Another interesting technique introduced in this paper is the aggregation of statistical information in networks, using sparse network decompositions and Chernoff bounds. 1 Introduction Motivati..

On-line admission control and circuit routing for high performance computing and communication

This paper considers the problems of admission control and virtual circuit routing in high performance computing and communication systems. Admission control and virtual circuit routing problems arise in numerous applications, including video-servers, real-time database servers, and the provision of permanent virtual channels in large-scale communications networks. The paper describes both upper and lower bounds on the competitive ratio of algorithms for admission control and virtual circuit routing in trees, arrays, and hypercubes (the networks most commonly used in conjunction with high performance computing and communication). Our results include optimal algorithms for admission control and virtual circuit routing in trees, as well as the first competitive algorithms for these problems on non-tree networks. A key result of our research is the development of on-line algorithms that substantially outperform the greedy-based approaches that are used in practice