Physical-Layer p-Cycles Adapted for Router-Level Node Protection: A Multi-Layer Design and Operation Strategy

We study an idea for efficient integrated protection of an IP over WDM network using the spare capacity of span-protecting p-cycles to provide protection against both optical link failures and router node failures in the IP/MPLS layer. Previously, networks using span-protecting p-cycles were designed from the point of view of a single-layer physical transport network. Also separately, it has been known how to plan capacity allocations to IP-layer logical links to support controlled levels of bandwidth oversubscription on transiting traffic flows through a failed router or ATM node. To address both failure types, however, it is unattractive to simply combine the two investments in added protection capacity. Accordingly, we have studied ways to plan a 100% span-restorable set of physical-layer p-cycles so that very high levels of transiting traffic flow can also be restored upon MPLS router node failure, with controlled worst-case oversubscription of LSP capacity allocations. In test cases it was found that the spare capacity provided by span-protecting p-cycles can provide a high level of node protection depending on the strategy used for exploring the p-cycle capacity. We think this leads to novel and efficient strategies for multi-service and multi-layer survivable traffic engineering and bandwidth management