A Multiperiod Capacity Planning Model for Backbone Computer Communication Networks

The cost of transmission capacity constitutes a significant portion of the total investment cost of a backbone computer communications network. In this paper, we address the problem of deciding where, when and how much transmission capacity should be installed, over a multiperiod horizon, to meet increasing traffic requirements at minimum total discounted cost, while maintaining acceptable performance levels. The model allows traffic among existing nodes to increase, new nodes to be added to the network, and its topology to change, over time. It is formulated as an integer programming problem, and a Lagrangian relaxation based solution method is proposed. Capacity and routing decisions are made jointly over time in our multiperiod model. Furthermore, our method automatically provides numerical verification of solution quality through the Lagrangian lower bound. Computational experiments with several networks show that the method yields verifiably good solutions to this combinatorially explosive problem.