An enhanced ILP design model for node-encircling p-cycle networks

We develop a new enhanced ILP design model that optimally designs a node-encircling p-cycle network. The new model takes advantage of the observation that NEPCs assigned solely for node-failure protection will inherently protect all two-hop segments of every multi-hop working lightpath. As a result, only single-hop working lightpaths need explicit span-failure protection in the conventional manner. The new ILP shows a significant reduction in capacity requirements.