Quality of protection through control-message scheduling in optical mesh networks

This paper considers the problem of providing quality of protection (QoP) classes in DWDM networks that use mesh-based path restoration schemes with capacity sharing. We focus on the signaling process required for reconfiguring the nodes along the pre-planned restoration paths, and propose a novel approach for meeting the QoP requirements by coordinating the set-up procedures for the backup paths through scheduling. We present a mixed integer-linear program (MILP) formulation for maximizing the number of connections that meet their QoP-class-specific restoration time deadlines. We also present a priority-based online scheduling method that uses simple connection and/or class-specific information and can be easily implemented with minor modifications to the currently proposed signaling protocols. We apply this method to signaling protocols that require cross-connect configurations at different nodes to be done in sequence as in the current GMPLS specification, as well as signaling protocols that allow cross-connect configurations to be done in parallel. It is shown that in both cases, significant performance improvements are achievable through scheduling in terms of the QoP grades that can be supported with both the MILP solutions and the heuristic. The improvement in restorability through our heuristics can be quite high (e.g., increase from a network restorability performance of 40% to a network restorability of 88%).