Segment p-cycle design with full node protection in WDM mesh networks

Segment p-cycles offer an interesting compromise between the classical (link) p-cycles and the path p-cycles (also known as FIPP p-cycles), inheriting most advantages of both p-cycle schemes. In their original form, segment p-cycles do not offer 100% node protection, i.e., do not guarantee any protection against node failure for the endpoints of the segments. Indeed, if we allow some p-cycle overlapping, it is possible to ensure 100% node protection: this is the focus of the present study. We propose a new efficient design approach for segment p-cycles, called segment Np-cycles, which ensure 100% protection against any single failure, either link or node (endpoints of requests are excluded). In order to evaluate the performances of segment Np-cycles, we develop a new optimization model based on column generation (CG) techniques. The use of such techniques eliminates the need to explicitly enumerate all segment Np-cycle configurations, but instead leads to a process where only improving segment Np-cycle configurations are generated. Numerical results demonstrate that segment Np-cycles are comparable, sometimes even more efficient, than path p-cycles with respect to their capacity requirement. In addition, in order to ensure 100% node protection, they only require a marginal extra spare capacity than the regular segment p-cycles.