A CP-LP approach to network management in OSPF routing

In this paper, we consider a routing problem related to the widely used Open Shortest Path First (OSPF) protocol, which is considered a challenge within the Constraint Programming (CP) community. We address the special version of OSPF which requires unique and symmetrical paths. To solve this problem, we propose a novel hybrid approach which combines CP and Linear Programming (LP). Our approach employs a new global constraint with problem-specific filtering algorithms to efficiently remove inconsistent values from partial solutions. Moreover, this constraint employs two LP relaxations which are used to indicate in-feasible 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.