Concurrent multi-layer restoration scheme for GMPLS based WDM networks

Next generation backbone networks will likely consist of IP routers as well as optical cross connects and will deploy Generalized Multiprotocol Label Switching (GMPLS) as the control plane protocol. The fiber carries large volume of traffic and therefore one must ensure that adequate mechanisms are in place that facilitate automatically recovery from failures. In mission critical networks survivability becomes critical. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense the published work recovers first in the optical domain and then proceeds to recover in the IP plane. We report for the first time a recovery procedure that recovers concurrently in both the optical and IP planes. The work on concurrent recovery investigates a single link failure scenario. While formulating the concurrent recovery protocol, we realized that modifications or extensions were needed to OSPF-TE protocol employed with GMPLS-based WDM networks. The OSPF-TE extension requires that the link state information propagated by the protocol must also carry available unused lambda label switched paths (lambdaLSPs). After a link failure, the ingress node upstream from failed link will first determine the availability of free light paths and existing unreserved bandwidth in used light paths from the link state information provided by OSPF extension. The concurrent multilayer recovery scheme proposed here uses this information to switch traffic in both optical and IP layer concurrently. An OPNET-based simulation study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.