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CP-LP Hybrid Method for Unique Shortest Path Routing Optimization

In this paper, we consider a routing problem related to the widely used Open Shortest Path First (OSPF) protocol. We address the special version of OSPF which requires unique and symmetrical paths. To solve this problem, we propose a hybrid approach which combines Constraint Programming (CP) and Linear Programming (LP). Our approach employs some new constraint with problem-specific filtering algorithms to efficiently remove inconsistent values from partial solutions. Moreover, we use two LP relaxations to indicate infeasible partial solutions due either to network capacity constraints, or to protocol-specific routing constraints. We show the efficiency of our complete approach on backbone networks with hundreds of different demands to route.