Studying how the various parameters of BitTorrent can be adjusted to improve the overall efficiency, and proposing improvements to the protocol only makes sense if deficiencies of the protocol or significant room for improvements are identified. We decided in this study to make the step before, i.e., to explore how BitTorrent is behaving on real torrents. We found in particular that the last piece problem, which is one of the most studied problem with proposed improvements of BitTorrent is in fact a marginal problem that cannot be observed in our torrent test.
Understanding BitTorrent: An Experimental Perspective by Arnaud Legout, Guillaume Urvoy-Keller and Pietro Michiardi, INRIA Technical Report, 2005 September