Shortest Path Versus Multihub Routing in Networks With Uncertain Demand

We study a class of robust network design problems motivated by the need to scale core networks to meet increasingly dynamic capacity demands. Past work has focused on one of two models. First, design the network for the known point-to-point peak demands. Second, design the network to support all hose matrices (all matrices not exceeding marginal bounds at the nodes). Both models may be too conservative if additional information on traffic patterns is available. We introduce a capped hose model to explore a range of traffic scenarios, which includes the above two as special cases. It is known that optimal network designs for the hose model are always determined by single-hub routing, and for the fixed-demand model are based on shortest-path routing. We demonstrate that a wider variety of routing templates is required to address the broader spectrum of capped hose matrices. We propose the use of hierarchical multihub routing templates, a generalization of hub and tree routing. Our empirical analysis is based on a heuristic for the resulting robust network design problem. These lead to two important findings: 1) designs based on multihub routing are often preferable to both hub and shortest path; 2) it may be possible for a carrier to sample their traffic in order to determine which type of routing is most cost-effective for their network.