In 802.11 WLANs, adapting the contention parameters to network conditions results in substantial performance improvements, but very few approaches have been validated in a realistic deployment. In this talk, we’ll present our experiences with implementing and evaluating two adaptive algorithms based on control theory, one centralized and one distributed, in a large-scale testbed consisting of 18 commercial off-the-shelf devices. We’ll present extensive measurements, considering different network conditions in terms of number of active nodes, link qualities, and data traffic, and show the inherent limitations of distributed schemes, and the good properties of centralized approaches.