# Congestion-Free Rerouting of Flows on DAGs

Changing a given configuration in a graph into another one is known as a reconfiguration problem. Such problems have recently received much interest in the context of algorithmic graph theory. We initiate the theoretical study of the following reconfiguration problem: How to reroute k unsplittable flows of a certain demand in a capacitated network from their current paths to their respective new paths, in a congestion-free manner? This problem finds immediate applications, e.g., in traffic engineering in computer networks. We show that the problem is generally NP-hard already for k = 2 flows, which motivates us to study rerouting on a most basic class of flow graphs, namely DAGs. Interestingly, we find that for general k, deciding whether an unsplittable multi23 commodity flow rerouting schedule exists, is NP-hard even on DAGs. Our main contribution is a polynomial-time (fixed parameter tractable) algorithm to solve the route update problem for a bounded number of flows on DAGs. At the heart of our algorithm lies a novel decomposition of the flow network that allows us to express and resolve reconfiguration dependencies among flows.

Top- Amiri, Saeed Akhoondian
- Dudycz, Szymon
- Schmid, Stefan
- Wiederrecht, Sebastian

Category |
Paper in Conference Proceedings or in Workshop Proceedings (Paper) |

Event Title |
45th International Colloquium on Automata, Languages, and Programming (ICALP) |

Divisions |
Communication Technologies |

Subjects |
Informatik Allgemeines |

Event Location |
Prague, Czech Republic |

Event Type |
Conference |

Event Dates |
July 2018 |

Date |
July 2018 |

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