Abstract: A cooperant improved algorithm is proposed，aiming at the problem of unfairness caused by the inaccurate estimation of the round trip propagation delay at the time of simultaneous connections of multiple FAST TCP．The synchronization back--of clock and the minimum back-of factor were determined via the full use of the locally available information cooperantly．W ithout direct communication of the FAST connections，the true propagation delay was accurately and quickly estimated，and the fairness was achieved for the buffer queue to empty occasionally．The NS-2 simulation results demonstrate that compared with other related algorithms，this improved algorithm can achieve fairness and higher stability．

Key words: fairness；propagation delay；local inform ation；cooperant；synchronization back-of clock