Heuristics for dimensioning large-scale MPLS networks

MultiProtocol Label Switching (MPLS) technology allows the support of multiple services with different Quality of Service (QoS) requirements in classical IP networks. In an MPLS domain, packet flows belonging to a particular class are classified in the same Forward Equivalence Class (FEC). Based on different FECs, each service can be set up in the network through logical networks. Each logical network is a set of Label Switched Paths (LSPs), one for each service traffic trunk. The network-dimensioning problem is formulated as the determination of routes for all LSPs to achieve the least cost physical network. To solve this problem some widely known heuristics are used and two enhancement algorithms are proposed that allow for significant gains when compared with the basic heuristics. The heuristics tested include a genetic algorithm, a greedy based heuristic and a lagrangean relaxation based heuristic. The enhancements are proposed for application to the greedy based heuristic and to the lagrangean heuristic. The results show that the enhanced lagrangean heuristic is the best overall technique for the case studies presented. This technique yields significant average gains when compared to the basic lagrangean heuristic.