Optical networks carrying traffic belonging to different survivability classes must ensure not only the proper survivability differentiation but also the efficient network resource utilization. Current approaches improve network resource utilization by carrying low-class preemptable traffic along high-class spare resources, which are idle (i.e., unutilized) during failure-free conditions. In this paper, the proposed idle protection capacity reuse (IR) framework generalizes the practice of reutilizing idle spare resources to both failure-free and failure conditions. The IR framework is based on the idea of exploiting idle high-class lightpath protection resources not only for routing low-class lightpaths during the provisioning phase (i.e., provisioning-phase IR, P-IR) but also for dynamically restoring low-class lightpaths during the recovery phase (i.e., recovery-phase IR, R-IR). Both P-IR and R-IR have the potential to improve network utilization while providing multiclass lightpaths with the required survivability differentiation. The numerical evaluation shows that the utilization of R-IR in dynamic restoration results in an improved low-class lightpath survivability with respect to the utilization of stub release. Moreover, if P-IR and R-IR are alternatively exploited, then the former improves the provisioning performance, while the latter guarantees a higher survivability. In the end, if P-IR and R-IR are concurrently employed in the provisioning and in the dynamic restoration of two different low classes of lightpaths, respectively, an inherent survivability differentiation is achieved.

© 2007 IEEE

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