1. A network usage optimization method, comprising the steps of: (a) providing a network and a data processing apparatus, wherein the data processing apparatus communicates via a permanent virtual circuit (PVC) of the network; (b) obtaining past network traffic data for traffic over the PVC; (c) predicting future network traffic data for traffic over the PVC for a future time period based on the past network traffic data; and (d) based on the predicted future network traffic data, determining and specifying an optimum CIR for the PVC for the future time period that will result in a minimum predicted total network usage fee for the future time period, said determining the CIR for the PVC for the future time period being performed by a processor of a computer system, wherein step (c) comprises: specifying a percentage; comparing traffic over the PVC between a first past time period and a second past time period; comparing traffic over the PVC between a third past time period and a fourth past time period; and in response to both a first traffic difference between the first and second past time periods and a second traffic difference between the third and fourth past time periods being less than the specified percentage, using traffic data of a fifth past time period as predicted traffic data over the PVC for a future time period.