Dynamic LSP routing in IP/MPLS over WDM networks

We consider an IP/MPLS over WDM network, in which label switched routers (LSRs) in the IP/MPLS layer are interconnected through optical cross-connects (OXCs) in the optical core network (WDM layer) providing an end-to-end wavelength routing capability. In this paper, we study a dynamic label switched path (LSP) routing problem for the three different network models of the IP/MPLS over WDM network, namely, Overlay, Augmented, and Peer models. For the overlay model, we propose two algorithms: ECF_OVLY and MLH_OVLY. In ECF_OVLY, a network always tries to use existing capacity first, whereas in MLH_OVLY, a network finds a path with the minimum number of logical hops for an LSP request. We also propose, for the augmented model, two simple and efficient dynamic LSP provisioning algorithms, called MCPI_AUG and DCPI_AUG, utilizing different type/amount of summarized capacity information from the WDM layer, namely Minimum CaPacity Information (MCPI) and Detailed CaPacity Information (DCPI). We compare the proposed algorithms with the existing algorithms available for the overlay [1] and peer [2], [3] models. The algorithms are compared and evaluated using two key performance measures: LSP blocking probability and network (lightpath) utilization. Simulation results show that at low loads with a limited number of ports available in the network, DCPI_AUG achieves an order of magnitude better blocking performance than the algorithm in [2] and outperforms the one in [3] by more than three times. It also achieves higher network utilization than the one in [2] by more than 10 % and the one in [3] by 2-7 % depending on the traffic load. Considering the small amount of information that is exchanged between the layers in the augmented model, these results suggest that the augmented model can be a practically good compromise between the overlay and peer models.