One looks at the derivative of the queue length. If that derivative continues in the positive direction, you can proactively send a congestion signal and ask the flows to slow down before the queue size reaches “congestion levels”. It is the theory behind almost all control systems, and was the idea behind the design of the PI controller.
RED was reactive, it waited for the average queue length to rise above a threshold and that introduced too much of a delay. PI is pro-active, it predicts onset of congestion and responds quickly. -Vishal -- http://www.cs.columbia.edu/~misra/ > On Apr 28, 2015, at 9:49 AM, Mikael Abrahamsson <[email protected]> wrote: > > So "incipient congestion" doesn't compute at all. I understand this term has > been used before, but that doesn't help me understand the reasoning behind > the wording. For me sending a congestion signal, means saying there is > congestion. It's not saying there is developing congestion (whatever that > might be).
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