Additive increase Multiplicative Decrease (AIMD)
This is a method of probe-and-adjust that some TCP implementations use.
- Every RTT it wants to increase the window size by 1.
- If there is congestion on the network it halves the window size.
As the window size is really in bytes rather than packets and we would like incremental progress rather than waiting for a full RTT. We increment the window size using the maximum segment size (MSS) proportionally to the current CongestionWindow size on every acknowledged packet using the formula: