An additive increase/multiplicative decrease congestion control algorithm has the property that the effect of a packet loss gets larger as the congestion window

An additive increase/multiplicative decrease congestion control algorithm has the property that the effect of a packet loss gets larger as the congestion window increases. There will be a point where the upward and downward forces on the congestion window balance out. The actual congestion window will oscillate around that. Assuming packet loss halves the congestion window while a packet delivery increases the congestion window by 1/cwnd, the break-even point for 1% packet loss is at a congestion window of 14. (1% change of reducing congestion window by 7, 99% chance of increasing it by 0.07). At 100ms RTT the average delivery rate will then be about 14 packets/rtt * 1500 bytes/packet * 10 rtts/second = 200kB/s. What if we cut down the packet loss rate by a factor of 10, to 0.1%? It won't give a 10x speed increase; instead the break-even point for the congestion window will be about 45; only a 3x increase in speed. If RTT is constant, increasing speed by 10x would require reducing packet loss by 100x. (The math here is simplified, but should suffice for illustrating this).