[Codel] [Cake] hard limit codel

Jonathan Morton chromatix99 at gmail.com
Thu Apr 16 08:00:21 EDT 2015

> On 16 Apr, 2015, at 14:50, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> I'll add, though, that I have seen the sentiment expressed here ("we
> need to limit the max delay of CoDel") in other contexts. And, well,
> delay spikes *is* a problem!

Yes, they are.

But in general AQM can’t be used to solve that problem without also suffering poor throughput; combining AQM with FQ *does* solve it.  Just like FQ is unfair to single flows competing against a swarm, but classifying the swarm traffic into a separate traffic class fixes that problem too.

Which of course is why cake uses AQM, FQ *and* Diffserv, all at once.

The linked paper didn’t measure HLC against fq_codel, even though they mention fq_codel.  That’s a major shortcoming.

 - Jonathan Morton

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