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

Sebastian Moeller <moeller0@gmx.de> Thu, 18 June 2020 08:15 UTC

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From: Sebastian Moeller <moeller0@gmx.de>
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Date: Thu, 18 Jun 2020 10:15:28 +0200
Cc: Paul Vixie <paul@redbarn.org>, TSVWG <tsvwg@ietf.org>, Ingemar Johansson S <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>
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To: Jonathan Morton <chromatix99@gmail.com>
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Subject: Re: [tsvwg] path forward on L4S issue #16
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Hi Jonathan,

good point below, which basically adds one more really important test condition to the already long list of missing tests for L4S:

A) Saturated multi-hop paths (individually saturated for both down- and upload direction)
B) Bi-directionally saturated path
C) asymmetric paths (including A) and B) conditions)
D) tests over real internet paths, coast to coast in the US, as well as trans-european and trans-asia paths
E) paths with wifi links
F)...

But in all likelihood we will just see more tests for those conditions L4S is known to work reasonably well for, short RTT and/or low hop count, tests of the download direction with at best the download direction experiencing congestion...

Best Regards
	Sebastian




> On Jun 18, 2020, at 10:07, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 18 Jun, 2020, at 10:38 am, Sebastian Moeller <moeller0@gmx.de> wrote:
>> 
>> …the idea that a single hop is typically responsible for all delay variation seems like too strong a claim to me…
> 
> It's quite easy to construct a counterexample, too: any network path including two wifi hops.  Wifi is inherently a significant source of delay variation due to its shared-medium, half-duplex, CSMA/CA with ARQ architecture.  So even if the rest of that network path introduces no delay variation at all, there are still two hops independently introducing delay variations.
> 
> - Jonathan Morton
>