Probing-Based Approaches to Bandwidth Measurements and Network Path Emulation

University dissertation from Uppsala : Acta Universitatis Upsaliensis

Abstract: The current Internet design is based on a number of principles and paradigms. A central theme of these is that the interior of the network should provide a very simple but generic (and optimized) service, namely best-effort packet forwarding. For the users, a consequence of this design is that performance properties and the behavior of the network can typically only be determined by performing probing-based measurements.Probing means that special packets are injected into the network by one computer while another one receives and collects statistics about those packets. Using this statistical information, it is possible to make inferences about the network and its characteristics. One important characteristic is the bandwidth that is available on the network path between two computers in the Internet. When communicating with each other, the computers should not persistently send data at a higher rate than the available bandwidth since that will eventually lead to packet loss due to the overload.This thesis considers the problem of measuring the available bandwidth of a network path using probing-based methods. To that end, we propose a new method called TOPP. It is designed to probe the network non-intrusively so that the measurements do not jeopardize the stability of the network. In addition to estimating the available bandwidth, TOPP also provides an estimate of the link capacity of the link that limits the available bandwidth.In the second part of this thesis we propose and evaluate different models for trace-driven network path emulation. We also investigate how to probe a network path for the purpose of trace-driven emulation. We show that relatively simple trace-driven models work well for non-responsive UDP-based flows. However, for adaptive TCP flows, these simple models do not seem to perform well. We also find that for the trace-driven models studied, strongly bursty probing schemes (which includes probing by TCP) have undesirable properties and should be avoided.

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