An Offline Hybrid IGP/MPLS Traffic Engineering Approach under LSP Constraints

MPLS (Multi-Protocol Label Switching) enhances the possibility to engineer the traffic on IP networks by allowing explicit routes. Though IGP (Interior Gateway Protocol) routing has proven its scalability and reliability, effective traffic engineering (TE) has been difficult to achieve in public IP networks, because of the limited functional capabilities of conventional IP technologies. Without MPLS there are in general two possibilities to perform TE in IP networks: either by improving the existing routing protocols, or by optimizing the parameters used for routing decisions in order to obtain better load distributions. In this work we propose a novel hybrid IGP/MPLS traffic engineering method based on genetic algorithms, which can be considered as an offline TE approach to handle long or medium-term traffic variations in the range of days, weeks or months. In our approach the maximum number of hops an LSP may take and the number of LSPs which are applied solely to improve the routing performance, are treated as constraints due to delay considerations and the complexity of management. We apply our method to the German scientific network (B-WiN) for which a traffic matrix is available and also to some other networks with a simple demand model. We will show results comparing this hybrid IGP/MPLS routing scenario with the result of pure IGP routing and that of a full mesh MPLS with and without flow splitting. keywords : routing, traffic engineering, metaheuristics, evolutionary computation, IP networks, MPLS