Minimizing protection switching time in transport networks with shared mesh protection

Abstract

Shared mesh protection (SMP) protects service traffic on a working path and requires coordinated use of the shared resources on a protection path when the traffic is routed through the protection path. If there are many intermediate nodes on the protection path, the delay caused by the coordination at each node increases the protection switching time, resulting in losing more traffic. Considering the capacity of a link and the bandwidth required by the protection paths using that link, it appears that coordination is necessary. However, looking closely at the relationships with other links and their protection paths, there exist resources that may require no coordination at all. This observation leads to the fact that protection switching time can decrease when bypassing some intermediate nodes for coordination. This fact introduces an optimization problem, in which the objective is to exclude these resources as much as possible from the set of resources for which coordination is required. A sub-problem is finding these excludable candidate resources. For both the main problem and the sub-problem, which are NP-hard, we propose a greedy algorithm and a branch-and-bound algorithm, respectively. The simulations show that the results using the proposed algorithms are near-optimal. Furthermore, in an actual topology configured with the SMP environment, the protection switching time is improved by excluding resources for which coordination is not required, compared to the existing Optical Transport Network (OTN) SMP mechanism.