p2-Cycles: p-Cycles with Parasitic Protection Links

The p-cycle and its Failure Independent Path Protection (FIPP) extension are known to be efficient and agile protection strategies. The p-cycle is preconfigured such that if there is a failure, only the switches at two end nodes need to be reconfigured. In this paper, we extend the p-cycle by allowing cycles to have attached links, called Parasitic Protection Links (PPL), in order to protect paths whose source and destination nodes are not only located on the cycle but also connected by the PPL to the cycle. A p-cycle with PPL is named p2-cycle. We address the unicast service protection problems against single-link failures by using p2-cycle in mesh networks and the problem is formulated as an Integer Linear Program (ILP). The numerical results show that the p2-cycle scheme provides better capacity efficiency than the FIPP p-cycle scheme in all the traffic scenarios considered and consumes 2.7%-14.8% extra total cost over the optimum, provided by Shared Backup Path Protection (SBPP) approach. Moreover, we study the failure recovery performance by comparing it to FIPP and SBPP in terms of average number of reconfigurations (NOR). The results achieved by the p2-cycle is less than that of SBPP in every scenario considered and the number reduces from 2.48 to 2.31 comparing to 2, achieved by FIPP, as the traffic demands increases in NSFNET. In conclusion, the p2-cycle provides greater overall performance over existent p-cycle-based and path-based protection schemes, especially when the number of traffic demands is large.