Define the following variables: Smax: the maximum increment Smin: the minimum increment wmax: the maximum window size β: multiplicative window decrease factor cwnd: congestion window size bic_inc: window increment per RTT (round trip time)
At every RTT interval update cwnd with the following: If no packets are dropped, the congestion window (cwnd) increases in three distinct ways: binary search increase, additive increase, and slow start. In each step, one is used as an increment.
One step of increasing cwnd: if (cwnd max) // binary search OR additive bic_inc = (wmax - cwnd) / 2; else // slow start OR additive bic_inc = cwnd - wmax; if (bic_inc > Smax) // additive bic_inc = Smax; else if (bic_inc min) // binary search OR slow start bic_inc = Smin; cwnd = cwnd + (bic_inc / cwnd); If one or more packets are dropped, the cwnd is reduced using
multiplicative decrease. This requires β, which is used in decreasing cwnd by (100×β)%. In the case of two flows, one with a large cwnd and the other a small cwnd,
fast convergence is used to decrease the greater cwnd flow's wmax at a greater rate than the smaller cwnd's flow to allow faster convergence of the greater cwnd's flow when increasing its cwnd.
One step of decreasing cwnd: if (cwnd max) // fast convergence wmax = cwnd * (2-β) / 2; else wmax = cwnd; cwnd = cwnd * (1-β); ==See also==