Survivable Network Design Models Based on Pre-Cross-Connected Trails

Survivability is a key issue in the design of optical mesh networks. Various survivability schemes have been introduced among which p-cycle has been attracting quite a lot of attention because of its fast and efficient protection capability. The concept of p-cycle was later generalized to pre-cross-connected trails or p-trails, by noting to the fact that providing pre-cross-connected protection paths and obtaining fast restoration does not require a cyclic structure. In this paper, we investigate the capability of p-trails in protecting traffic demands in a mesh-based survivable network. By taking the sharing capability of p-trails into account, we introduce optimization models to verify the remarkable efficiency of p-trails. We derive two ILP models for survivable network design using p-trails. In our first model, the optimal solution is obtained from a candidate set constructed by exhaustive enumeration of all simple trails. We observe that the size of our ILP model, and therefore the computation time, become prohibitively large making the model unpractical for larger network instances. Therefore, to overcome this scalability issue, we develop a better model for this complex optimization problem using a primal-dual decomposition of the original problem based on the column generation (CG) optimization method. Our developed design approach is shown to be very scalable, as opposed to other prior p-trail design methods; further, we show that p-trails are more efficient than p-cycles in terms of resource redundancy in the network.