On the Convergence of the Link-state Advertisement Protocol in Survivable Wdm Mesh Networks

Survivability in the dynamic IP over WDM network may be guaranteed by the Shared Path Protection (SPP) scheme implemented at the optical layer. The advantages of this scheme are fast recovery obtained at the lowest possible layer and efficient bandwidth utilization obtained by sharing spare resources. The paper investigates the performance of a dynamic distributed bucket-based SPP scheme in conjunction with a modified version of the link-state advertisement OSPF protocol, whose goal is to control the amount of signaling overhead. The objective of the study is to assess the blocking probability of the proposed scheme due to lack of resources, and identify the exact causes of such blocking, i.e., link-state convergence, working lightpath blocking, and protection lightpath blocking. Simulation results show that inaccurate database information, i.e., slow convergence of the link-state advertisement protocol, may significantly contribute to the connection blocking probability unless adequate frequency of the OSPF updates is chosen.