Simulation is a fast, controlled, and reproducible way to evaluate new algorithms for distributed computing platforms in a variety of conditions. However, the realism of simulations is rarely assessed, which critically questions the applicability of a whole range of ndings. In this paper, we present our eorts to build platform models from application traces, to allow for the accurate simulation of le transfers across a distributed infrastructure. File transfers are key to performance, as the variability of le transfer times has important consequences on the dataow of the application. We present a methodology to build realistic platform models from application traces and provide a quantitative evaluation of the accuracy of the derived simulations. Results show that the proposed models are able to correctly capture real-life variability and signicantly outperform the state-of-the-art model.