Applying the policy concept to avoid logical race conditions in multilayer network restoration

Protection switching interactions in wide-area networks need to interoperate with each other in order to restore a wide variety of service types, provide survivability to mission-critical applications and accommodate an evolving network infrastructure. Without some coordination between restoration mechanisms, an outage duration would be lengthened as methods assigned to each layer interfere with each other or the network would be locked up in a deadlocked state that never converges to a new topology. A set of control policies can be specified to coordinate between restoration mechanisms in a network that spans multiple layers and regions. These control policies are expressed as rules, and are collectively denoted as the escalation strategy. The escalation strategy can be provisioned by a network manager and is implemented as a distributed coordination protocol between peer recovery agents in the nodes. As rules for coordinating between restoration mechanisms are formalized, a mathematical proof could be provided to prove that the network does indeed converge to a new topology