Automated adaptive on-line Multi-Layer Traffic Engineering through “tailoring” wavelength-paths in the Fragment Graph

In Multi-Layer networks, where more than one layer is switched, i.e., connections are set up using not only the upper, e.g., IP layer but the underlying wavelength layer as well leads often to suboptimal performance due to long wavelength paths, that do not allow routing the traffic along the shortest path. The role of MLTE (Multi-Layer Traffic Engineering) is to cut (fragment) these long wavelength-paths into parts (fragments) that allow better routing at the upper layer, or to concatenate (defragment) two or more fragments into longer paths when the network load is low and therefore fewer hops are preferred.In this paper we present a new model, the Fragment Graph (FG) and an algorithm for this model that supports Fragmentation and De-Fragmentation of wavelength paths making the network always instantly adapt to changing traffic conditions. We introduce the notion of shadow links   to model “λλ-path tailoring”. We implicitly assume that the wavelength paths carry such, e.g., IP traffic that can be interrupted for a few milliseconds and that even allows minor packet reordering.To show the superior performance of our approach in various network and traffic conditions we have carried out an intensive simulation study where we compare blocking ratios and path lengths and we analyze the dynamic behavior and fairness of the proposed and of reference methods.