Evaluating available bandwidth estimation methods requires a malleable MAC protocol implementation, precise MAC layer packet timing measurements, and the ability to create control topologies in laboratory setups so that not all nodes are within communication range. To address these challenges, we have exploited IEEE 802.11e-derived features to obtain more control over the MAC layer operation of off-theshelf radios and implemented a measurement-system that uses CPU timestamp counter and radio

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... dware timestamps to monitor MAC activity with microsecond resolution. In addition to presenting performance of our available bandwidth estimation method using packet probes, we also discuss solutions and open issues to provide useful information for other testbed cross-layer protocol evaluations, which are likely to face similar challenges.