Beating the logarithmic lower bound: Randomized preemptive disjoint paths and call control algorithms

Ran Adler*, Yossi Azar

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review

Abstract

We consider the maximum disjoint paths problem and its generalization, the call control problem, in the on-line setting. In the maximum disjoint paths problem, we are given a sequence of connection requests for some communication network. Each request consists of a pair of nodes, that wish to communicate over a path in the network. The request has to be immediately connected or rejected, and the goal is to maximize the number of connected pairs, such that no two paths share an edge. In the call control problem, each request has an additional bandwidth specification, and the goal is to maximize the total bandwidth of the connected pairs (throughput), while satisfying the bandwidth constraints (assuming each edge has unit capacity). These classical problems are central in routing and admission control in high speed networks and in optical networks. We present the first known constant-competitive algorithms for both problems on the line. This settles an open problem of Garay et al. and of Leonardi. Moreover, to the best of our knowledge, all previous algorithms for any of these problems, are Ω(log n)-competitive, where n is the number of vertices in the network (and obviously non-competitive for the continuous line). Our algorithms are randomized and preemptive. Our results should be contrasted with the Ω(log n) lower bounds for deterministic preemptive algorithms of Garay et al. and the Ω(log n) lower bounds for randomized non-preemptive algorithms of Lipton and Tomkins and Awerbuch et al. Also, non-constant lower bounds proved by Canetti and Irani for randomized preemptive algorithms for related problems emphasize the distinction between problems that have constant competitive algorithms and other that do not.

Original languageEnglish
Pages1-10
Number of pages10
StatePublished - 1999
EventProceedings of the 1999 10th Annual ACM-SIAM Symposium on Discrete Algorithms - Baltimore, MD, USA
Duration: 17 Jan 199919 Jan 1999

Conference

ConferenceProceedings of the 1999 10th Annual ACM-SIAM Symposium on Discrete Algorithms
CityBaltimore, MD, USA
Period17/01/9919/01/99

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