Maximizing connection availability in wavelength division multiplexing (WDM) networks is critical because even small disruptions can cause huge data losses. However, there is a trade-off between the level of network survivability and the cost related to the backup resources to be provided. One-hundred percent survivability can be achieved by dedicated path protection (DPP) with multiple prereserved protection paths for each provisioned connection, i.e., DPP (). Unfortunately, the blocking probability performance of DPP () is negatively affected by the large number of prereserved backup wavelengths standing by unutilized. On the other hand, path restoration (PR)-based solutions ensure good blocking performance at the expense of lower connection availability. The work in this paper aims at finding hybrid network survivability strategies that combine the benefits of both techniques (i.e., high availability with low blocking rate). More specifically, the paper focuses on a double link failure scenario and proposes two strategies. The first one couples DPP () with path restoration (referred to as ) to minimize the number of dropped connections. The second scheme adds the concept of backup reprovisioning (BR), referred to as , in order to further increase the connection availability achieved by . Integer linear programming models for the implementation of the proposed schemes are formulated. Extensive performance evaluation conducted in a path-computation-element-based WDM network scenario shows that and can significantly lower the blocking probability value compared to DPP () without compromising too much in terms of connection availability.
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