Re: [tsvwg] Follow-up to your DSCP and ECN codepoint comments at tsvwg interim

Sebastian Moeller <> Sun, 08 March 2020 16:31 UTC

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Date: Sun, 08 Mar 2020 16:34:18 +0100
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To: Bob Briscoe <>, tsvwg IETF list <>, Steven Blake <>
From: Sebastian Moeller <>
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Subject: Re: [tsvwg] Follow-up to your DSCP and ECN codepoint comments at tsvwg interim
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Hi Bob,

More below.

On March 8, 2020 3:23:39 PM GMT+01:00, Bob Briscoe <> wrote:
>On 07/03/2020 19:16, Sebastian Moeller wrote:
>>> Anyway, if user B's downstream is the bottleneck for user A, even if
>>> ISP
>>> B doesn't bleach Diffserv, the DSCP is still no use if ISP A
>>> or if an intermediary does.
>> 	[SM] That really just would show that there is a business case for
>ISP A and B to connect directly in a DSCP conserving fashion....
>This is a misunderstanding of the sequencing of adoption incentives. If
>something new doesn't work in the scenarios of interest, it will never 
>take off, and never affect anyone's business cases for doing anything.

[SM] That might pass as a cogent argument, but for the fact that ISPs (and CDNs) already use SLAs to define their interactions, e g. for VoIP traffic. The incremental effort to also include a LL-type traffic class/dscp seems pretty minor to me.

I also strongly believe that the only incentive for an ISP to roll-out L4S would be if that additional work/expense can be monetized, and the most viable route for that I can see, is to discrimination-free sell L4S access to the deploying ISP's eyeballs to all interested content suppliers, be it directly or via CDNs. In that case an SLA is not only not going to be a stumbling block, but rather a mandatory component of making this work.

What kind of deployment are you realistically expecting where this is going to be an issue?

And especially for the scope of the experimental deployment? The experiment is required to make sure that L4S can deployed in a safe and backward compatible fashion and that it can deliver it's promises under real-world conditions.
The experiment is NOT about how to deploy something in a fashion that offers the least part of resistance/the highest adoption rate. As a rule of thumb, I would assume the IETF be interested in the technical aspects and not the marketing side....



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