[Cake] Running Cake at long RTTs

Toke Høiland-Jørgensen toke at toke.dk
Wed Oct 28 11:36:57 EDT 2015

Sebastian Moeller <moeller0 at gmx.de> writes:

> Except I requested rtf 120 ms and got 122.7, which admittedly is
> close. I know I repeat myself, but on of the is one things that
> irritate me in software is if software silently pretends to know
> better… Now 122.7 versus 120 might be in the noise, but look at that:

I don't remember from where, but I suspect there's something wrong with
the 'change' logic in Cake. Can you try removing the qdisc completely,
then re-adding it, rather than doing a straight replace?

Might not be that, but do try it out just to be sure. I have not looked
at the scaling of target/interval that goes on in the different bands;
but there is one? Or is there? If there is, why? It's not immediately
obvious that different diffserv markings needs different settings for
the AQM...

> Also I notice the disparity between parameter name “rtt” and the name
> of the reported statistic “interval”. Jonathan, Dave, what is your
> preference change the reported stats name or the parameter name (I
> believe it should be that statistic that needs renaming).

Yes, if we're calling it RTT it should be RTT throughout. I do think
that makes more sense than interval.

> Next question what is the opinion on exposing target in addition to
> interval? My point, which I might have over-repeated already, is we
> should expose and honor it if possible. (Any with honor I mean replace
> the 5ms default but do all calculations as cake usually does for
> different priority bands; that also means that if only one of interval
> or target where specified cake is free to scale the other one to what
> it considers reasonable).

I seem to recall that at some point we has "easy to configure" as a goal
of Cake.


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