Re: [tsvwg] L4S vs SCE

Greg White <> Wed, 20 November 2019 10:48 UTC

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From: Greg White <>
To: Kyle Rose <>, Ingemar Johansson S <>
CC: G Fairhurst <>, "" <>, Ingemar Johansson S <>, "" <>, "De Schepper, Koen (Koen)" <>, "" <>
Thread-Topic: [tsvwg] L4S vs SCE
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Date: Wed, 20 Nov 2019 10:48:14 +0000
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Subject: Re: [tsvwg] L4S vs SCE
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In the case of Low Latency DOCSIS, the network operator will need to explicitly configure L4S “on” via the cable modem configuration file or the Aggregate QoS Profile table on the CMTS, and then reboot the cable modem.  If there is a need at some future point to discontinue L4S support, an operator could do so quickly by reverting the configuration to disable L4S, then rebooting the cable modem.  Additionally, CableLabs would write an Engineering Change against the DOCSIS spec to deprecate the feature and remove the ability from the CMTS to enable the feature on cable modems that continue to support it.

From: tsvwg <> on behalf of Kyle Rose <>
Date: Wednesday, November 20, 2019 at 6:14 PM

On Wed, Nov 20, 2019 at 6:04 PM Ingemar Johansson S <<>> wrote:
>       How do you expect an industry/commercial roll-out of L4S
> technology to behave, if the L4S experiment should terminated without
> adoption as a standard track RFC? Are they supposed to phase-out using
> ECT(1) as well, or is it understood that deployed L4S instances continue using
> L4S methods?

[IJ] The premise would be that L4S is declared a failure. I doubt that anybody has a good enough crystal ball to predict what happens. First it is necessary to come to the conclusion that L4S is a failure and I would argue that we are not yet there and I don't currently see that coming. Before that possible event I don't see it meaningful to speculate.

I'm going to have to go ahead and disagree with you strongly here. Given the potential consequences of cleaning up after a failed experiment without a plan worked out beforehand, this blithe approach is simply not acceptable.

In lots of cases, experiments are easy to terminate in an obvious way: for example, in one typical case, a code point can simply be abandoned, or (even better) a pollutable experimental code point returned to the available pool after some time. If that were the case here, it would not be difficult to enumerate a sequence of steps required to do so. It doesn't appear that's the case, however, so all the more reason to make sure we address this as part of the experiment setup.

A launch escape system of the necessary complexity should be a requirement of any experimental deployment. In this case, that might circumscribe the scope of the experiment itself.