Internet protocol (IP) traffic follows rules established by routing protocols. Shortest path based protocols, such as Open Shortest Path First (OSPF), direct traffic based on arc weights assigned by the network operator. Each router computes shortest paths and creates destination tables used for routing flow on the shortest paths. If a router has multiple outgoing links on shortest paths to a given destination, it splits traffic evenly over these links. It is also the role of the routing protocol to specify how the network should react to changes in the network topology, such as arc or router failures. In such situations, IP traffic is re-routed through the shortest paths not traversing the affected part of the network. This paper addresses the issue of assigning OSPF weights and multiplicities to each arc, aiming to design efficient OSPF-routed networks with minimum total weighted multiplicity (multiplicity multiplied by the arc length) needed to route the required demand and handle any single arc or router failure. The multiplicities are limited to a discrete set of values and we assume that the topology is given. We propose an evolutionary algorithm for this problem, and present results applying it to several real-world problem instances.
AT&T Labs Research Technical Report TD-64KUAW, September 6, 2004.