Shared-segment protection offers a good compromise between shared link and path protection. In this paper, we further investigate segment protection with respect to, (i) the pre-configured pre-cross connected p-cycle protection scheme, (ii) the evaluation of the additional required CAPEX cost in order to enhance protection against single link failures with node protection, and (iii) the comparison with path p-cycles in terms of the failure recovery time.

We propose a new protection scheme, segment Np-cycles (segment p-cycles with full node protection). We design a novel scalable CAPEX optimization model for the optimal design of segment Np-cycles. We next investigate the best trade-off between regular segment protection (segment p-Cycles) and the proposed Np-cycles within the p-cycle protection framework. Last, we develop formulas for calculation of the recovery time for each of the three p-cycle protection schemes, p-cycles, Np-cycles and path p-cycles.

Numerical results show that protection against single node failures can be ensured with about 3% extra CAPEX and no more than 3.2% extra spare capacity, throughout an adaptation of segment p-cycles. This suggests that segment Np-cycles constitute an attractive protection scheme for protection against single node or link failures. In contrast with path p-cycles, segment Np-cycles can reduce the network-wide longest recovery time by 25%, and the average recovery time by 10%. They are more capacity efficiency in sparse networks although they may have a higher CAPEX cost.