The Trade-Offs between Optimality and Feasibility in Online Routing with Dedicated Path Protection in Elastic Optical Networks

The article discusses an online problem of routing and spectrum allocation with dedicated path protection in elastic optical networks. We propose three novel algorithms to solve this problem. The first of them is the minimum-cost–maximum-flow heuristic algorithm, which calculates the solution assuming that the spectrum units on the working and dedicated backup path are the same. Such an assumption, on the one hand, increases the bandwidth blocking probability; however, on the other hand, it enables a simple, cheap and fast way to connect customers to the network during the implementation phase of elastic optical networks. The next two algorithms, which determine the exact solutions, are based on the branch and bound method. The first calculates the working and dedicated backup paths with the minimum total occupied bandwidth, called the total cost, while the second calculates the paths with the minimum total length. These algorithms enable the performance evaluation of the proposed heuristic algorithm and provide the answer as to what should be optimized, the total cost or the total length of paths, in order to minimize the bandwidth blocking probability. Extensive simulation research has shown that the proposed heuristic algorithm can be used in elastic optical networks, but with a small network load. Moreover, it is shown that the optimization of the total cost of paths provides a slightly lower blocking probability than the optimization of the total length of paths.