Improving network simulation with feedback

Since the publication of the article by Leland, Taqqu, Willinger and Wilson (1993) it has become well known that real network traffic does not follow a Poisson process and that feedback mechanisms in a network affect the traffic patterns. Yet much modeling and simulation work employs exponential interarrivals in open-loop traffic sources. Historically these sources were chosen because they are amenable to analysis and easy to simulate, but they have serious shortcomings. Even when the source distribution is changed to reflect the burstiness of real traffic, we found that open-loop models fail to reproduce the detailed time structure and the crucial effects of feedback on traffic sources. An evaluation of a hybrid fiber coax (HFC) architecture is used to illustrate the inadequacy of traditional open-loop modeling. In addition, a promising intermediate technique of using "local feedback" is shown. Finally using feedback models, the interaction of the HFC architecture with TCP dynamics was studied using Web-browsing and file transfer applications. These studies led to a novel architectural improvement that would have been missed in an open-loop model.