Impact of idle protection capacity reuse on multi-class optical networks

In a multi-class traffic scenario spare resources can be utilized, under normal network conditions, for the transmission of low class traffic. In this way network resource utilization is improved but, upon failure occurrence, low class connections are preempted by recovered high class connections. On the other hand spare resources, allocated to protect high class connections but not utilized (i.e., idle) in a specific failure scenario, can be employed to recover failed low class connections. In this case low class connections resort to dynamic restoration because they carry traffic that tolerates not to be recovered or to experience long recovery time. In this study a scenario is envisioned where, besides high (i.e., gold) class connections, which are shared path protected, two alternative low class connections are present in the network: silver and bronze class connections. Both silver and bronze connections exploit dynamic restoration to overcome failures. The main difference is that silver connections utilize high class spare resources just after failure occurrence while bronze connections utilize high class spare resources before and after the failure. Numerical results show a tradeoff between provisioning and restoration performance of the different connection classes in the considered scenarios. If spare resources are exploited only after the failure (i.e., gold-silver scenario), low class connection survivability is high. If spare resources are used also during normal network operation (i.e., gold-bronze scenario), the provisioning performance of both connection classes is improved, but, upon failure occurrence, the low class survivability is low. In both scenarios, the inaccurate network state information after the failure slightly degrades survivability performance.