Strategies for enhanced dual failure restorability with static or reconfigurable p-cycle networks

We suggest methods for achieving high dual-failure restorability in p-cycle networks that are optimally designed only to withstand all single failures, or have minimized amounts of additional capacity for dual failure considerations. In one set of circumstances we consider static p-cycles (that cannot be rearranged once established) and propose strategies to enhance the dual-failure restorability based on concepts of failure spreading and limiting the maximum number of protection relationships of any p-cycle. We then consider the case of reconfigurable p-cycles, in which the spare capacity can be reconfigured dynamically, creating a new set of p-cycles that are optimized to withstand possible second failures. Results show significant improvements of the dual-failure restorability obtained by limiting the number of protection relationships in static design. For 100% dual-failure restorability, p-cycle reconfiguration reusing most of the existing p-cycles and adding some new ones appears to be the most promising approach.