Configuration of reserved delivery subnetworks

We introduce the concept of a Reserved Delivery Subnetwork (RDS) to allow an information service provider to deliver a higher quality of service to its customers. A network provider implements an RDS by provisioning reserved bandwidth on paths from a central site to distributed locations, where customers of the information service are located. The amount of bandwidth reserved is a function of the mean and variance of the traffic expected at the various locations. To configure an RDS, the network provider must select the links to be included and must dimension the reservations on those links appropriately. Network resource usage can often be reduced by routing flows destined for nearby cities along common paths. We show that the problem can be formulated as a minimum cost network flow problem with a concave cost function (one where the cost per unit flow decreases as the flow increases), which is a well-known NP-hard optimization problem. We introduce an approximate solution method and evaluate it experimentally. Our results are typically within a small factor of an easily computed lower bound. Keywords—Reserved delivery services, minimum concave cost network flows, approximation algorithms.