Given a graph with nonnegative edge weights and node pairs Q, we study the problem of constructing a minimum weight set of edges so that the induced subgraph contains at least K edge-disjoint paths containing at most L edges between each pair in Q. Using the layered representation introduced by Gouveia (1998), we present a formulation for the problem valid for any K, L ≥ 1. We use a Benders decomposition method to efficiently handle the big number of variables and constraints. We show that our Benders cuts contain the constraints used by Huygens et al. to formulate the problem for L = 2,3,4, as well as new inequalities when L ≥ 5. While some recent works on Benders decomposition study the impact of the normalization constraint in the dual subproblem, we focus here on when to generate the Benders cuts. We present a thorough computational study of various branch-and-cut algorithms on a large set of instances including the real based instances from SNDlib. Our best branch-and-cut algorithm combined with an efficient heuristic is able to solve the instances significantly faster than CPLEX 12 on the extended formulation.

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Given an undirected graph, we study the problem of finding K edge-disjoint paths, each one containing at most L edges, between a given pair of nodes. We focus on the case of K = 2 and L = 3. For this particular case, previous known compact formulations are valid only for the case with non-negative edge costs. We provide the first compact linear description that is also valid for general edge costs. We describe new valid inequalities that are added to a well known extended formulation in a layered graph, to get a full description of the polyhedron for K = 2 and L = 3. We use a reduction of the problem to a size-2 stable set problem to prove this second property.