Davide Cherubini - PhD Thesis - UniCA Eprints

3.2 Optimization of MPLS routingmodifies the utilization of the network making small changes in the traffic splittingratios, operating directly in the routers configuration. This approach couldgenerate instability of the network, with a consequent loss of performances, whenthe traffic matrix rapidly changes.3.2 Optimization of MPLS routingFrom the introduction of the MPLS technology in the telecommunication world,many works to optimize the traffic engineering techniques have been proposed.The main objective of these papers is to find the optimal LSPs configurationthat minimizes different objective functions, such as the total congestion of thenetwork, the total mean delay, or the maximum number of hops in an LSP.In [58] several heuristics used to search the optimal LSPs distribution minimizingthe maximum utilization of the network are compared.In [65] the authors use the same approach of [64] in order to minimize themaximum link occupation or the total mean delay of the network. Basically, thelink loads are periodically measured and the traffic is gradually dislocated fromthe congested part of the network toward the less congested one. The adaptivealgorithm has been applied to small networks and does not consider the impactof the link failure.In [26], Tabu Search is used to find a layout of MPLS paths with the minimumnumber of hops, while in [39] the routing problem for MPLS networks is representedas an off-line multiobjective Mixed Integer Programming that looks forthe best trade-off between the minimal routing delay, the optimal load balancing,and the minimal splitting of traffic trunks.In [38] and in the following paper by the same authors [23] a multipath adaptivetraffic engineering mechanism is introduced. The approach aims to avoidnetwork congestion by adaptively balancing the load among multiple paths basedon measurement and analysis of path congestion level.In [63] the author presents a novel algorithm based on Simulated Annealingto optimize OSPF link metrics and, in a successive step, two Mixed Integer Programming(MIP) models, to setup complementary MPLS paths, are proposed.Basically, the majority of traffic is routed along the OSPF shortest paths and it16