Re: [tsvwg] path forward on L4S issue #16

Sebastian Moeller <moeller0@gmx.de> Tue, 09 June 2020 14:56 UTC

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From: Sebastian Moeller <moeller0@gmx.de>
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Date: Tue, 9 Jun 2020 16:56:20 +0200
Cc: Jonathan Morton <chromatix99@gmail.com>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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References: <HE1PR0701MB2876AA3CBBA215B9FB895B0AC2820@HE1PR0701MB2876.eurprd07.prod.outlook.com> <3637517F-63A0-4862-9885-AB5EA7E6C273@gmail.com> <VI1PR0701MB2877E21B7F406C3DFCFF08BCC2820@VI1PR0701MB2877.eurprd07.prod.outlook.com> <92525827-39B6-4E88-B453-660F8FE22523@gmx.de> <VI1PR0701MB287768D465C37DC46A459C12C2820@VI1PR0701MB2877.eurprd07.prod.outlook.com>
To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
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Subject: Re: [tsvwg] path forward on L4S issue #16
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Hi Ingemar,


> On Jun 9, 2020, at 16:43, Ingemar Johansson S <ingemar.s.johansson@ericsson.com> wrote:
> 
> Hi
> Why don't you run the testing yourself to get the answers you look for?. 

	[SM] Good question. But I believe you are taking this as a scream question, while I consider this to be an L4S question. I am fine with scream being a research project and all, not having gone out of its way to test all possible adversarial traffic patterns, after all nobody is forced to use scream.
	With the envisioned roll-out of L4S as the "mandatory" CC of the future of the whole internet, the situation looks quite different IMHO. Mandatory here does not mean that everybody is forced to actively use L4S-aware transport protocols, but that all traffic traversing a L4S hops will suffer the consequences.

> 
> You can download and build the SCReAM BW test tool (follow the steps below).
> I can guarantee that you'll find cases where it does not work In a
> satisfactory way. But as with most other congestion control work it is work
> in progress, sometimes that progress is good, sometimes not so good due to
> other projects that are more important.

	[SM] +1; please accept my apology, I did not want to diss scream in any way here, I really just want to re-focus the discussion on the issues I see with L4S and its lack of sufficient realistic testing. Again, for scream as mostly a research vehicle this is fine, and asking me to roll up my sleeves and get into testing is good advice. Now, if L4S would be just a research vehicle we would not even have this discussion.

Best Regards
	Sebastian


> 
> /Ingemar
> ==============================
> How to get and build the SCReAM BW test tool on Linux PC's
> 
> cd ~/somewhere 
> git clone https://github.com/EricssonResearch/scream.git
> cd code/bw-test-tool
> cmake .
> make
> 
> What needs to be installed in advance is
> git
> cmake 
> make
> gcc (or g++ ?) I install both
> 
> Read the SCReAM-BW-test-tool.pptx
> ==============================
> 
>> -----Original Message-----
>> From: Sebastian Moeller <moeller0@gmx.de>
>> Sent: den 9 juni 2020 16:21
>> To: Ingemar Johansson S
>> <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>
>> Cc: Jonathan Morton <chromatix99@gmail.com>om>; Ingemar Johansson S
>> <ingemar.s.johansson@ericsson.com>om>; tsvwg@ietf.org
>> Subject: Re: [tsvwg] path forward on L4S issue #16
>> 
>> Ingemar,
>> 
>> I have a feeling that this discussion thread is based on a disconnect. I
> believe
>> that most here agree that Scream is a nice and interesting project worth
>> pursuing. The only contentious point is whether scream working well with
>> current L4S AQM behavior over a single simulated hop, can make up for the
>> apparent lack of testing under even mildly adversarial conditions (aka
> real
>> internet conditions) of the core L4S implementation and design. If you
> have
>> made such measurements in the context of scream's development, please
>> do not hesitate to present them here.
>> 
>> incomplete listing of mildly adversarial conditions:
>> 1) bi-directionally saturating traffic
>> 2) asymmetric links
>> 3) long networks paths, >>5 hops
>> 4) paths with parallel segments
>> 5) unfriendly greedy traffic with less than expected yielding behavior ...
>> 
>> Data demonstrating L4S immunity against negative behaviour under any of
>> these conditions, is IMHO quite helpful for the continuing discussion.
>> 
>> Best Regards
>> 	Sebastian
>> 
>> 
>> 
>>> On Jun 9, 2020, at 16:11, Ingemar Johansson S
>> <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org> wrote:
>>> 
>>> Jonathan, you kick in open doors..
>>> 
>>> I urge interested people (if any?) to follow the discussion thread
>>> instead to get an understanding what causes the lower throughput with
>> L4S.
>>> https://mailarchive.ietf.org/arch/msg/tsvwg/FFQH_XG0-
>> wbLIt7JRJ33dH8Fyf
>>> c/
>>> 
>>> /Ingemar
>>> 
>>>> -----Original Message-----
>>>> From: Jonathan Morton <chromatix99@gmail.com>
>>>> Sent: den 9 juni 2020 12:10
>>>> To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
>>>> Cc: tsvwg@ietf.org
>>>> Subject: Re: path forward on L4S issue #16
>>>> 
>>>>> On 9 Jun, 2020, at 10:33 am, Ingemar Johansson S
>>>> <ingemar.s.johansson@ericsson.com> wrote:
>>>>> 
>>>>> "Even though it is more than a magnitude difference in queue delay
>>>>> between CoDel-ECN and L4S, it is fair to say that these simple
>>>>> simulations should of course be seen as just a snapshot."
>>>> 
>>>> Not to mention a magnitude difference in throughput.
>>>> 
>>>> - Jonathan Morton
>