Technical Report 2002-037

Trace-Driven Network Path Emulation

Bob Melander and Mats Björkman

November 2002

This paper reports on on-going work where a trace-driven approach to network path emulation is investigated. Time stamped probe packets are sent along a network path whereby a probe packet trace can be generated. It basically contains the send times and the one-way delays/loss indications of the probe packets. Inside the emulator, the probe packet trace is used by a loss model and a delay model. These determine if a packet should be dropped or what the delay of the packet should be. Three loss models and three delay models are evaluated. For non-responsive UDP-based flows, the trace-driven loss and delay models that determine loss and delay based on loss-rates and delay distribution parameters calculated across the probe packet trace using a small gliding window are found to perform best. For adaptive TCP flows, none of the evaluated trace-driven models performs well. Instead, the Bernoulli loss model and an independent average delay model performs best.

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