Design of Flexible Protection Plans in Survivable WDM Networks: An Application to PWCE

We propose a new flexible design approach of protection plans in survivable WDM networks by using protection structures with no predefined shapes in order to maximize the protected working capacity in an end-to-end basis. Previous design approaches of survivable WDM based on Protected Working Capacity Envelope (PWCE) have looked at the optimization problem of maximizing the protected capacity on a link basis, independently or the source and destination nodes of the potential traffic. Moreover, those approaches have only investigated the design problem with pre-configured protection cycles (p-cycles). Our design approach proposed in this paper differs from those previously proposed in two main points: (sic) We use pre-configured protection structures (p-structures) with no predefined shapes. By using protection structures with unrestricted shapes, we want to identify the most flexible ones, i.e., those that can provide the highest protected capacity even within constrained spare capacity budget or low network connectivity. (sic) We maximize the availability of the protected capacity on an end-to-end basis rather than on a link basis. This allow us to more efficiently track fluctuation of the traffic in the networks and among nodes. In order to deal with the large solution space, we develop an ILP optimization model, and use an efficient large scale optimization tool called the Column Generation tool (CG). Results show that a design based on unrestricted p-structure patterns is similar to 10% less capacity redundant, similar to 15% more reliable, and allow recovery along shorter backup paths compared to the p-cycle based scheme.