Topological design of MPLS networks

The paper addresses the IP/MPLS network cost optimization problem of selecting localizations of nodes and links, combined with links' dimensioning. As MPLS is flexible in routing demands' flows through the network, the considered problem is similar to the classical NP-hard topological design problems dealt with in the past, mostly in the context of the road traffic. We assume that the network nodes are composed of two disjoint sets: the set of access nodes (Label Edge Routers) and the set of transit nodes (Label Switching Routers). The access (end) nodes only generate demands and do not transit end-to-end demands' flows, while the transit nodes do not generate demands but do transit the flows. The selection of the actually installed transit nodes and the links interconnecting (all) network nodes is the major subject of optimization. As the considered problem is hard, we discuss and propose branch-and-bound based solution methods. The effectiveness of the methods is illustrated by means of a numerical study.