10 After‐Failure‐Repair Optimization

Lluís Gifre1, Filippo Cugini2, Marc Ruiz1 and Luis Velasco1

1 Universitat Politècnica de Catalunya, Barcelona, Spain

2 CNIT, Pisa, Italy

As discussed in Chapter 8, capacity usage in dynamic Elastic Optical Networks (EONs) may not be optimal due to the permanent process of setting up and tearing down of connections, which might lead to spectrum fragmentation and, as a result, to increased connection blocking. On top of this, a restoration mechanism that is triggered in reaction to a link (or node) failure restores the affected lightpaths (see Chapter 9); eventually, when the link is repaired, and its capacity becomes available for new connections, the unbalance between lightly and heavily loaded links increases, thus further decreasing the probability of finding optical paths with continuous and contiguous spectrum for future connection requests. In this chapter, we study the effects of reoptimizing the network after a link failure has been repaired (namely, the AFRO (after‐failure‐repair optimization) problem), as an effective way for both reducing and balancing capacity usage and, by these means, for improving network performance. Illustrative numerical results show that AFRO allows to significantly decrease the request blocking probability in realistic dynamic network scenarios. Besides, traffic disruptions resulting from lightpath rerouting are practically negligible. From the recovery perspective, using multiple paths (named as ...

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