On the single-source unsplittable flow problem

Yefim Dinitz, Naveen Garg, Michel X. Goemans

Research output: Contribution to journalArticlepeer-review

98 Scopus citations

Abstract

Let G = (V, E) be a capacitated directed graph with a source s and k terminals ti with demands di, 1 ≤ i ≤ k. We would like to concurrently route every demand on a single path from s to the corresponding terminal without violating the capacities. There are several interesting and important variations of this unsplittable flow problem. If the necessary cut condition is satisfied, we show how to compute an unsplittable flow satisfying the demands such that the total flow through any edge exceeds its capacity by at most the maximum demand. For graphs in which all capacities are at least the maximum demand, we therefore obtain an unsplittable flow with congestion at most 2, and this result is best possible. Furthermore, we show that all demands can be routed unsplittably in 5 rounds, i.e., all demands can be collectively satisfied by the union of 5 unsplittable flows. Finally, we show that 22.6% of the total demand can be satisfied unsplittably. These results are extended to the case when the cut condition is not necessarily satisfied. We derive a 2-approximation algorithm for congestion, a 5-approximation algorithm for the number of rounds and a 4.43 = 1/0.226-approximation algorithm for the maximum routable demand.

Original languageEnglish
Pages (from-to)17-41
Number of pages25
JournalCombinatorica
Volume19
Issue number1
DOIs
StatePublished - 1 Jan 1999

ASJC Scopus subject areas

  • Discrete Mathematics and Combinatorics
  • Computational Mathematics

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