double check some results

steven's suggestion:
1. check cwnd convergence with a longer duration of the simulation (done. due to a script bug which grab cwnd_ and cwnd_cut_ into cwnd. Other results are all valid).
2. single flow to see what's the queue distribution
3. use c/n, instead of c, to recalculate the burst size.
4. measure the RTT loss rate for small flow and for large flow.