In this paper, we propose a new approach to network bandwidth estimation based on System Dynamics modelling. The paper discusses existing approaches to bandwidth estimation and network capacity planning. Limitations of these approaches are presented and the case for using System Dynamics is made. Applicability of the proposed approach is demonstrated through a real world network planning project for a distributed logistics application. A practical computer simulation model was developed to predict bandwidth requirements for the projectís network. This model provides system planners with the ability to test different possible scenarios in order to make informed decisions about the system architecture. We show through practical results of the simulation runs and the insights gained during the process that the System Dynamics approach offers an effective solution to the problem of network bandwidth estimation and system planning. The paper concludes with a review of the results and pointers for further research.