Re: [rmcat] Still looking for reviews of draft-ietf-rmcat-nada

Michael Welzl <michawe@ifi.uio.no> Sat, 05 August 2017 11:56 UTC

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From: Michael Welzl <michawe@ifi.uio.no>
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Date: Sat, 5 Aug 2017 13:56:35 +0200
Cc: Anna Brunstrom <anna.brunstrom@kau.se>, "Xiaoqing Zhu (xiaoqzhu)" <xiaoqzhu@cisco.com>, "Flohr, Julius" <julius.flohr@uni-due.de>, "Sergio Mena de la Cruz (semena)" <semena@cisco.com>, "rmcat@ietf.org" <rmcat@ietf.org>, "draft-ietf-rmcat-nada@ietf.org" <draft-ietf-rmcat-nada@ietf.org>
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To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
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Subject: Re: [rmcat] Still looking for reviews of draft-ietf-rmcat-nada
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+1, of course  :-)
i (naturally) liked seeing this in SCREAM, and I do think the logic of ABE (draft-ietf-tcpm-alternativebackoff-ecn) applies to all RMCAT controls  (why wouldn’t it?).

So, thanks Ingemar for pointing this out!

Cheers,
Michael


> On Aug 5, 2017, at 12:06 PM, Ingemar Johansson S <ingemar.s.johansson@ericsson.com> wrote:
> 
> Hi
> Not sure that we are in full agreement, it is possible that I misunderstand.
> The estimation of marking ratio in section 5.1.2 in the NADA draft indicates a scalable reaction (read L4S). 
> 
> As I understand it, one cannot assume that classic ECN marking makes it possible to use a scalable response. What is possible to do is to use ECN marking events (one or more ECN marked packets in one window or RTT) as a signal to reduce the sending rate for instance 50% or whatever is deemed appropriate (see e.g. https://tools.ietf.org/html/draft-ietf-tcpm-alternativebackoff-ecn-01 ). 
> 
> Agree that we can leave L4S out of scope for the time being.
> 
> /Ingemar
> 
> 
>> -----Original Message-----
>> From: Anna Brunstrom [mailto:anna.brunstrom@kau.se]
>> Sent: den 26 juli 2017 03:06
>> To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>om>; Xiaoqing
>> Zhu (xiaoqzhu) <xiaoqzhu@cisco.com>om>; Flohr, Julius <julius.flohr@uni-
>> due.de>; Sergio Mena de la Cruz (semena) <semena@cisco.com>
>> Cc: rmcat@ietf.org; draft-ietf-rmcat-nada@ietf.org
>> Subject: Re: [rmcat] Still looking for reviews of draft-ietf-rmcat-nada
>> 
>> Hi Ingemar,
>> 
>> I think this is actually even more related to the feedback than the marking,
>> the "classic" feedback provided by TCP does not tell you how many marked
>> packets you have received. But as the RTCP feedback gives you per packet
>> information I think there will be no difference from when you have an AQM
>> with loss in this case?
>> 
>> L4S will give you a different marking, but I think that should be left out of
>> scope at the moment and treating lost and marked packets the same in
>> accordance with RFC 6679 is fine.
>> 
>> BR,
>> Anna (as an individual)
>> 
>> 
>> On 2017-07-25 09:22, Ingemar Johansson S wrote:
>>> Hi
>>> An errata...
>>> 
>>> Referring to "classic" AQMs like CoDel "It is AFAIK possible to
>>> accurately indicate the degree of congestion" should read "It is AFAIK
>>> not possible to accurately indicate the degree of congestion"
>>> 
>>> /Ingemar
>>> 
>>>> -----Original Message-----
>>>> From: Ingemar Johansson S
>>>> Sent: den 20 juli 2017 21:55
>>>> To: 'Xiaoqing Zhu (xiaoqzhu)' <xiaoqzhu@cisco.com>om>; Flohr, Julius
>>>> <julius.flohr@uni-due.de>de>; Sergio Mena de la Cruz (semena)
>>>> <semena@cisco.com>
>>>> Cc: Anna Brunstrom <anna.brunstrom@kau.se>se>; rmcat@ietf.org;
>>>> draft-ietf- rmcat-nada@ietf.org
>>>> Subject: RE: [rmcat] Still looking for reviews of
>>>> draft-ietf-rmcat-nada
>>>> 
>>>> Hi Xiaoqing + others
>>>> 
>>>> To your ECN question... This is tricky, if I understand things right
>>>> you tie NADA to a specific ECN marking algorithm. For instance CoDel
>>>> will display a completely different ECN marking behavior. The snag is
>>>> that with classic ECN marking like this you can only indicate the
>>>> existence of congestion. It is AFAIK possible to accurately indicate the
>> degree of congestion.
>>>> L4S is a different story as it allows to indicate the degree of congestion.
>>>> 
>>>> /Ingemar
>>>> 
>>>> 
>>>>> -----Original Message-----
>>>>> From: Xiaoqing Zhu (xiaoqzhu) [mailto:xiaoqzhu@cisco.com]
>>>>> Sent: den 20 juli 2017 19:48
>>>>> To: Flohr, Julius <julius.flohr@uni-due.de>de>; Sergio Mena de la Cruz
>>>>> (semena) <semena@cisco.com>
>>>>> Cc: Anna Brunstrom <anna.brunstrom@kau.se>se>; Ingemar Johansson S
>>>>> <ingemar.s.johansson@ericsson.com>om>; rmcat@ietf.org;
>>>>> draft-ietf-rmcat- nada@ietf.org
>>>>> Subject: Re: [rmcat] Still looking for reviews of
>>>>> draft-ietf-rmcat-nada
>>>>> 
>>>>> Catching up on this thread.
>>>>> 
>>>>> Thanks much to Julius, Ingmar, and Safiqul for reviewing this draft
>>>>> and providing your input.
>>>>> 
>>>>> Regarding Ingmar's comments:
>>>>> 
>>>>> * Page 8, computation of d_tilde and the risk of being locked in the
>>>>> loss- based mode due to non-linear warping:  fully agree that this
>>>>> is a limitation of the algorithm we should acknowledge in the draft.
>>>>> In the meanwhile would like to work with Julius to look into
>>>>> specific example failure cases, and hopefully derive further
>>>>> insights on how to better tune the algorithm parameters.  Will
>>>>> update both our ns3-rmcat implementation and NADA draft after that
>> investigation.
>>>>> 
>>>>> * Section 5.1.2 : Estimation of p_mark : as I understand your
>>>>> comments point to the fact that different ECN marking behaviors may
>>>>> occur and some (e.g.,
>>>>> L4S) may not interact well with NADA.  It is true that we have not
>>>>> tested NADA extensively against different variants of ECN markings
>>>>> --- the one's we've tried before are RED (marking instead of dropping).
>>>>> One way to help clarify that will be to point to our Appendix A.2 as
>>>>> the specific ECN marking behavior we expect, in Sec. 5.1.2.  Do you
>>>>> think that will address your concern?
>>>>> 
>>>>> And, thanks to Julius for sharing with us issues you've observed in
>>>>> your implementation efforts.  We've set up a separate email thread
>>>>> to meet up remotely and go over that in greater technical details.
>>>>> 
>>>>> Question back to the Chairs:  our plan now is to update both our
>>>>> draft (to address both sets of Ingmar's comments) and corresponding
>>>>> ns3
>>>>> open- source implementation, within a month.  Procedure-wise, are we
>>>>> expecting the updated version (-05) to go through WGLC again at that
>>>>> point?  Just trying to understand what to expect next.
>>>>> 
>>>>> Thanks,
>>>>> Xiaoqing
>>>>> 
>>>>> 
>>>>> 
>>>>> ________________________________________
>>>>> From: Flohr, Julius <julius.flohr@uni-due.de>
>>>>> Sent: Wednesday, July 19, 2017 6:19 AM
>>>>> To: Sergio Mena de la Cruz (semena)
>>>>> Cc: Anna Brunstrom; Ingemar Johansson S; rmcat@ietf.org;
>>>>> draft-ietf-rmcat- nada@ietf.org
>>>>> Subject: Re: [rmcat] Still looking for reviews of
>>>>> draft-ietf-rmcat-nada
>>>>> 
>>>>> Hi,
>>>>> 
>>>>>> On 19. Jul 2017, at 09:01, Sergio Mena <semena@cisco.com> wrote:
>>>>>> 
>>>>>> 
>>>>>> As for Julius's tests, we thank Julius for the effort put into it,
>>>>>> and would like
>>>>> to see how his results compare to our latest ones (see Slides
>>>>> presented by Xiaoqing in April's RMCAT interim).
>>>>> I haven't done too much testing, but as far as I can tell there is
>>>>> an issue when the bottleneck bandwidth is smaller than RMAX:
>>>>> If you have a competition scenario between NADA and a loss based
>>>>> flow, it seems that nada gets stuck in the competitive mode because
>>>>> itself creates queueing delay that is larger than QTH.
>>>>> 
>>>>> I actually made a little mistake when I said the problem has gotten
>>>>> worse compared to the last version of the draft. The issue actually
>>>>> has been introduced in version 03 with the introduction of TEXPLOSS.
>>>>> Before, the draft was very unclear and stated that one should warp
>>>>> the congestion signal IFF packet loss is present, but without stating a
>> time span.
>>>>> 
>>>>> Therefore the implementation just used the knowledge it had from the
>>>>> recent observation window LOGWIN (500 ms). That worked really well
>>>>> because it helped the algorithm to return to the normal mode of
>>>>> operation more easily, because after that timespan it would stop
>>>>> warping regardless whether there is lots of queueing delay present or
>> not.
>>>>> 
>>>>> I don't know if this is an issue with my implementation or if there
>>>>> is an actual issue with the algorithm, but this is what I have observed.
>>>>> 
>>>>> I'll contact Xiaoqing and Sergio directly so we can work together on
>>>>> this issue and post our findings to this mailing list directly.
>>>>> 
>>>>> Regards,
>>>>> 
>>>>> Julius
>>>>> 
>>>>> 
>>>>> =====================================
>>>>> Julius Flohr, M.Sc.
>>>>> University of Duisburg-Essen
>>>>> Computer Networking Technology Group
>>>>> 
>>>>> Room SL-408
>>>>> Schützenbahn 70
>>>>> D-45326 Essen/Germany
>>>>> 
>>>>> E-Mail:  julius.flohr@uni-due.de
>>>>> Phone: +49-201-183-7667
>>>>> Fax:     +49-201-183-7673
>>>>> =====================================
>>> 
>