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Re: [aqm] CoDel's control law that determines drop frequency

Toke Høiland-Jørgensen <toke@toke.dk> Wed, 30 September 2015 12:25 UTC

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From: Toke Høiland-Jørgensen <toke@toke.dk>
To: "Bless, Roland (TM)" <roland.bless@kit.edu>
References: <201311122230.rACMUBmH003536@bagheera.jungle.bt.co.uk> <87wpzfpbd3.fsf@alrua-karlstad.karlstad.toke.dk> <56045CA8.2060103@bobbriscoe.net> <CAPRuP3mmg_-uxmtLUXprCmPyLSUuUA7t2dRZpDs_mwtnTgrSQA@mail.gmail.com> <560BA261.6020206@bobbriscoe.net> <560BA7B9.8020800@student.kit.edu> <877fn8kttv.fsf@toke.dk> <560BD38C.5010806@kit.edu>
Date: Wed, 30 Sep 2015 14:25:12 +0200
In-Reply-To: <560BD38C.5010806@kit.edu> (Roland Bless's message of "Wed, 30 Sep 2015 14:20:28 +0200")
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Cc: Polina Goltsman <polina.goltsman@student.kit.edu>, Andrew Mcgregor <andrewmcgr@google.com>, Kathleen Nichols <nichols@pollere.com>, Bob Briscoe <ietf@bobbriscoe.net>, Van Jacobson <vanj@google.com>, AQM IETF list <aqm@ietf.org>
Subject: Re: [aqm] CoDel's control law that determines drop frequency
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"Bless, Roland (TM)" <roland.bless@kit.edu> writes:

> Am 30.09.2015 um 13:52 schrieb Toke Høiland-Jørgensen:
>> Polina Goltsman <polina.goltsman@student.kit.edu> writes:
>> 
>>>> Early on, Rong Pan showed that it takes CoDel ages to bring high load under
>>>> control. I think this linear increase is the reason.
>>>
>>> Is there a link to this ?
>> 
>> I have an analysis of transient behaviour in my recent paper (section 6.2):
>> http://www.sciencedirect.com/science/article/pii/S1389128615002479
>> 
>> PIE struggles with this too, BTW...
>
> Thanks for the pointer, but I guess that's a different issue.
> If I understood Bob correctly, he was referring to a steady state
> situation with many flows (=high load?) in congestion avoidance phase.
> But maybe Bob can clarify this...

Well, steady state has (by definition) nothing to do with how long it
takes to get there? Once CoDel has found the right scaling point it
stays there, so surely the problem is with transients?

-Toke

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