Region growing for multi-route cuts

TL;DR

This paper introduces new approximation algorithms for multi-route cut problems in graphs, extending region growing techniques to handle multiple connectivity thresholds, with specific results for 2-route cuts and general thresholds.

Contribution

It extends region growing methods to multi-route cut problems, providing the first non-trivial approximations for various variants including node and edge disjoint thresholds.

Findings

Polylogarithmic approximations for 2-route cut cases.

Bicriteria approximations for arbitrary thresholds.

Multiple algorithms with different cost-connectivity tradeoffs.

Abstract

We study a number of multi-route cut problems: given a graph G=(V,E) and connectivity thresholds k_(u,v) on pairs of nodes, the goal is to find a minimum cost set of edges or vertices the removal of which reduces the connectivity between every pair (u,v) to strictly below its given threshold. These problems arise in the context of reliability in communication networks; They are natural generalizations of traditional minimum cut problems where the thresholds are either 1 (we want to completely separate the pair) or infinity (we don't care about the connectivity for the pair). We provide the first non-trivial approximations to a number of variants of the problem including for both node-disjoint and edge-disjoint connectivity thresholds. A main contribution of our work is an extension of the region growing technique for approximating minimum multicuts to the multi-route setting. When the connectivity thresholds are either 2 or infinity (the "2-route cut" case), we obtain polylogarithmic approximations while satisfying the thresholds exactly. For arbitrary connectivity thresholds this approach leads to bicriteria approximations where we approximately satisfy the thresholds and approximately minimize the cost. We present a number of different algorithms achieving different cost-connectivity tradeoffs.