On Sun, Jun 14, 2015 at 11:07 AM, Jonathan Morton <[email protected]> wrote: > >> On 14 Jun, 2015, at 20:38, Dave Taht <[email protected]> wrote: >> >>> Every time Codel triggers the dropping state, it will mark or drop at least >>> one packet, and increment count by that number. With count decremented >>> only by 1 on recovery, it will effectively remain constant *if*, by some >>> miracle, the queue empties before the second signal was sent; it cannot >>> decrease between episodes unless it resets or wraps. >> >> It aint a miracle, it is hopefully within an rtt. > > No, it is *at minimum* one RTT. It takes that long for the congestion signal > to reach the receiver, be reflected back to the sender, the sender’s reaction > to *begin to* appear at the queue. Then the queue *starts* to empty, if the > signal is what’s required to make it do so.
Flows, btw, do end quite rapidly in the real world. What was it, 95% of all web flows ended inside of IW10? Dropping a packet at the tail end of an ending flow forces a retransmit. Far too much of our testing and thinking is oriented to full rate flows. That is what I meant by "hopefully". I would like to build a test that consisted primarily of short flows, one that hopefully looked more like normal traffic. >> When resuming the drop phase of codel, it is almost *already* too late >> to catch that burst incurring the latency. > > Yes, but that’s what FQ is for. And ELR, if we ever get that properly > started. > >> Sometimes I think we need to do away with the count idea and measure >> slopes of curves instead, and "harmonics”. > > >> Is there any reason why the decrease couldn't be some sort of decay? >> I.e. a function of how long ago the drop state was exited? > > Such things are theoretically possible, but require further thought to > determine how best to do them. > > - Jonathan Morton > -- Dave Täht What will it take to vastly improve wifi for everyone? https://plus.google.com/u/0/explore/makewififast _______________________________________________ Codel mailing list [email protected] https://lists.bufferbloat.net/listinfo/codel
