A Comparative Study of Fast Protection Schemes in WDM Mesh Networks

The concept of p-cycle (Preconfigured Protection Cycle) allows fast and efficient span protection in WDM mesh networks. Compared to a simpler-cycle, a non-simple p-cycle can traverse a node or span multiple times. As a result, non-simple p- cycles can better explore mesh connectivity of a network. On the other hand, the recently proposed PXT (Pre-Cross-Connected Trail) concept removes the cycle constraint by allowing arbitrary protection trails. In this paper, we carry out a comparative study among these fast protection schemes, and formulate ILPs (Integer Linear Programs) for non-simple p-cycle and PXT design. As far as we know, our ILP for non-simple p-cycle design is the first one without candidate cycle enumeration, and our ILP for PXT design is the first one proposed in this area. Based on our ILPs, we find simple, non-simple p-cycle and PXT solutions for a simple network. We show that the required spare capacity for 100% protection in each scheme is reduced in the same order above.