Avoiding blocking in multilayer recovery

With more options to recover traffic provided, based on services survivability requirements, providing an integrated recovery solution becomes critical. Layering has been a key driver in allowing network devices and technologies geared to carrying new types of services such as IP traffic over existing networks. Also, it has allowed networks to increase capacity by converting SONET to wavelengths. Providing connectivity is a key function of recovery, no matter what the layer. We expect that recovery capabilities will be added to client layers such as IP and MPLS and to server layers such as WDM. A primary goal of recovery is for all services traversing a failed link to be restored in a way consistent with businesses requirements. Inconsistent provisioning will prevent this. Furthermore, since recovery can occur at a different time than when it is provisioned, inconsistent provisioning is really determined after the fact, with services left unrepaired or repaired unnecessarily and at extra cost. Double redundancy will let different layers operate on the same traffic because of the containment relationship of units of traffic called encapsulation. In other words, recovery operates twice. We can ensure recovery meets a global perspective on how traffic should be restored by simply checking the provisioning at each device and checking suitable properties of a formal representation. In this paper, we propose a mapping from command-line interfaces to a topological representation that will allow us to check if provisioning is consistent.