Distributed Protocol for Removal of Loop Backs and Optimum Allocation of p-Cycles to Minimize the Restored Path Lengths

p-Cycle-based protection is one of the most promising techniques of span protection in optical networks because of mesh-like efficiency and ring-like speed. We have presented a modified distributed cycle preconfiguration protocol (MDCPC) which reduces the computational complexities, by finding all the copies of the same p-cycle in single iteration. All the copies of the same p-cycle are aggregated together to reduce the number of switching fabrics and the amount of signalling traffic. Further, the restoration paths provided by the p-cycles are usually many hops long, as longer p-cycles provide better efficiency. Obviously, with longer p-cycles, the nodes in the working path may be repeated in the restoration path provided by the p-cycle. They will give rise to loop backs in the restored path. The restored path lengths will unnecessarily be longer due to these loop backs. If these loop backs can be removed, the restored path length will be reduced significantly, and redundant capacity will also be released. In the present work, a distributed protocol has been presented for the implementation of removal of loop back (RLB) algorithm to reconfigure the restored path. The reduction in the restored path length also depends on the fact that which p-cycle is being used to protect a particular path. The problem has been formulated as optimum p-cycle allocation (OPA) problem and solved with the Hungarian algorithm. The average lengths of the restored paths with and without RLB for the networks with 2.0 average nodal degree have also been derived.