This paper investigates design methods of protection schemes in survivable WDM networks using the path protection -trail in order to provide better capacity efficiency by eliminating the rigidness of the protection structure of the well-accepted protection scheme, the failure independent path protection (FIPP) pre-configured protection cycle (-cycle). The flexibility in the protection structure yields lower cost in terms of spare capacity allocation while maintaining the high speed of protection switching. We develop two design approaches, the fully pre-cross-connected path protection trail (-trail) and the partially pre-cross-connected path protection trail (-trail), based on the degree of pre-cross-connectivity of the protection structure. In order to obtain optimally designed trails, we develop an optimization model based on a large-scale optimization technique, namely, column generation. Numerical results show that -trails significantly improve the spare capacity efficiency compared to the FIPP -cycle, and -trails strike a balance between capacity redundancy and recovery delay. We observe that -trails can achieve as low capacity redundancy as shared backup path protection (SBPP), while the recovery delay is kept lower than in SBPP and slightly higher than FIPP -cycles by using selective signaling through a control plane that is aware of the location of the cross-connects that are not pre-configured in advance.
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