An efficient and practical layer-preference policy for routing in GMPLS networks

We address the problem of routing Label Switched Paths (LSPs) in multi-layer networks based on the Generalized MultiProtocol Label Switching (GMPLS) paradigm. In particular, we pursue strategies for choosing the appropriate layer to host a new LSP request, since choosing this policy has enormous impact on the eventual performance of the network. Therefore, we developed a mixed strategy, the Min-phys-hop routing and wavelength assignment algorithm, as a policy to govern the selection of the best layer of a multi-layer network in which to host new LSP requests. In this paper, we discuss the practical issues concerning the deployment of this algorithm in modern GMPLS networks. Firstly, we discuss the applicability of the algorithm with respect to the state-of-the-art GMPLS standards, above all, the GMPLS routing extensions to OSPF-TE. We also sketch two possible reference deployment scenarios. Secondly, we present simulation studies to demonstrate that (1) there does not exist a universally optimal static layer-preference policy and (2) the Min-phys-hop algorithm realizes an adequate heuristics even considering the realistic limitations of contemporary network devices. We found that the Min-phys-hop algorithm produces close-to-optimal blocking and resource consumption under almost all possible selections of input parameters, and this is regardless of the wavelength and Optical-Electrical-Optical (OEO) conversion capability present in the network.