Capacity planning of DiffServ networks with best-effort and expedited forwarding traffic

For networks providing a specific level of service guarantees, capacity planning is an imperative part of network management. Accurate dimensioning is especially important in DiffServ networks, where no per-flow signaling or control exists. In this paper, we address the problem of capacity planning for DiffServ networks with only Expedited Forwarding (EF) and best effort (BE) traffic classes. The problem is formulated as an optimization problem, where the total link cost is minimized, subject to the performance constraints of both EF and BE classes. The variables to be determined are the routing of EF traffic, and the discrete capacities of the links. We show that Lagrangean Relaxation and subgradient optimization methods can be used to solve the problem. Computational results show that the solution quality is verifiably good while the running time remains reasonable on practical-sized networks. This represents the first work for capacity planning of multi-class IP networks with non-linear performance constraints.