Enabling Efficient Multi-Layer Repair in Elastic Optical Networks by Gradually Superimposing SDN

Multi-layer resilience is one of the prominent new concepts for modern carrier networks; it efficiently combines the advantages of the optical and the packet layer. However, not all features offered by modern optical transport networks can be fully used by the packet layer yet. In case of a fiber cut, an optical protection mechanism restores the original IP topology after a short transient time. But such an optical restoration is expected to use a new, longer light-path, which in turn might affect the optical capacity of the link. Bit-rate flexible optical transceivers are able to utilize the remaining optical capacity efficiently by adapting the network link capacity accordingly. However, the packet layer is not able to cope with fluctuating link capacities; often the policy is to rather shut down the link completely instead of using the remaining capacity. Consequently, this paper proposes a Segment Routing-based approach with superimposed Software defined Networking (SDN) to allow the IP network to benefit from these new features. The minimally invasive, gradual deployment of the system is investigated, while keeping other proven and resilient technologies and systems unmodified. Using the topology and traffic matrix of a large German carrier the feasibility of such a deployment is evaluated.