Design of efficient node p-cycles in WDM mesh networks

p-cycles have been extensively studied under a single link failure scenario. Even though not as common, single node failures may occur as well, and the resulting consequences can be devastating. Failure-Independent Path-Protecting (FIPP) p-cycles provide end-to-end path protection, and thereby protection against node failures, assuming that precautions are taken.In this paper, we propose enhanced p-cycles, called node p-cycles, different from the FIPP p-cycle scheme, which can guarantee 100% protection against any single node failure. We design a scalable optimization model, which relies on a column generation formulation, in order to design the enhanced node p-cycles.Extensive comparative experiments have been conducted after designing a column generation framework for all compared protection schemes, in order to guarantee scalable models for each of them. Experiments include the (link) p-cycles, the node p-cycles of Onguetou and Grover (2009) [16], our enhanced node p-cycles and the FIPP p-cycles. We show that node p-cycles offering node and link protection only require slightly more spare capacity than link p-cycles, while requiring sometimes less, sometimes more spare capacity than FIPP p-cycles. For the comparison with the work of Grover and Onguetou (2009) [2], results show that our new node p-cycle scheme clearly outperforms their design in terms of capacity efficiency.