Exploiting Failure Recovery for the Robust Support of two Service Classes in IP over WDM Networks

We analyze the gain obtained by deploying, in an IP-over-WDM network, two classes of service differentiated by their type of protection. The first one, called FP (Fully Protected), is protected at the WDM or SONET layer by a 1:1 protection strategy, while the second one, called BEP (Best Effort protected), offers no specific guarantee on service disruption is provided. In case of failure it offers to restore as much of the affected traffic as possible. Given an already routed FP traffic matrix, we maximize the amount of BEP traffic admitted in the network in both the regular operation, without any failure, and after a the occurrence of a single failure. The optimization procedure allows the operator to choose the weight he wants to give to these contradictory objectives. We develop an efficient heuristic for solving this problem on large networks. An interesting finding is that the choice of this weight has an important impact on the amount of BEP traffic that can be restored, but only in some range within .