In global client-server systems, some services may be offered by multiple hosts. In order for a client to select the host to which it can expect the highest possible bandwidth, a dynamic estimation of the available bandwidth has to be performed. This term project reviews the "Packet bunch modes" algorithm (PBM) developed by Vern Paxson at Berkeley and presents an implementation that is designed to allow dynamic bandwidth estimation in the Internet as well as the processing of TCP Traces. PBM provides a quite robust estimation of the bottleneck bandwidth, which serves as a basis for estimating the available bandwidth.
By running tests on several TCP Traces, the algorithm has been validated. The estimations of the bottleneck bandwidth have been compared to known values of link bandwidths and have been considered to be accurate enough. In contrast to that, the validataion of the estimations of the available bandwidth has turned out to be much more difficult and could not be completely covered within the scope of this term project. It remains to be examined in further experiments whether the algorithm is able to estimate the available bandwidth accurately enough. Performance optimizations and the implementation of a probing mechanism to use the algorithm in the Internet are also part of future work.
Cyrill Osterwalder
Stauffacherstr. 173
CH-8004 Zürich
EMail: costerwa@iiic.ethz.ch
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