Design of p-Cycles for Full Node Protection in WDM Mesh Networks

We propose a p-cycle expanded protection scheme that can guarantee 100% node protection, in addition to 100\% protection against single link failures. While some previous studies had already noted that p-cycles can naturally offer some node protection, we show that, at the expense of some p-cycle overlapping, with very mild impact on the bandwidth efficiency, one can guarantee node protection. We propose a design and solution method based on large scale optimization tools, namely Column Generation (CG), that compute p-cycles offering both link and node protection. Previous models offer a solution where a large number of potential cycles needs first to be enumerated, leading to very large ILP models which cannot scale. Comparisons are made between our proposed design approach with the work of Grover and Onguetou (2009). Results show clearly that our approach outperforms their design in terms of capacity efficiency and of the number of distinct cycles. We also evaluate the extra spare capacity requirement of p-cycles for full node protection compared to the one for link protection only. Results shows that p-cycles offering node and link protection only require a slightly larger capacity while the implicit protection against dual link failure is only marginally affected.