[Bloat] Notes about hacking on AQMs

Dave Taht dave.taht at gmail.com
Thu Jun 23 18:47:31 EDT 2011

On Thu, Jun 23, 2011 at 4:38 PM, Juliusz Chroboczek <jch at pps.jussieu.fr> wrote:
>> I will also attempt to argue persuasively that having ECN packet marking in HTB
> I'm not following you.  You can only perform ECN marking when you detect
> congestion; and you can only detect congestion if you're queueing.
> I may be wrong, but I believe that HTB doesn't do any queueing itself,
> it delegates queuing to its child qdiscs; hence, I don't see how you can
> perform ECN marking in HTB itself; you should be doing it in HTB's child
> qdisc.

You are right. I had spent a lot of time into HTB puzzling over how it
actually worked, observing lots of packet drops at it's level of stats
and nothing at the red level in the existing qos-scripts, and no
seeming correlation to the SFQ or hsfc either. It just didn't add up.

I'm still puzzling over it. But I grew to understand after posting
that mail that my issues were happening at the child qdiscs and I will
continue rewriting the rfc until it is both right AND clear.

Thx for catching up on the backlog.

>> RED has it's own idea as to the 'bandwidth' available, and does not
>> understand what it's getting has already been shaped by HTB.

> I'm not sure I understand that.

Neither do I and I'm going to go hide under a rock until I do.

> -- Juliusz

Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608

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