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Re: [tsvwg] DSCPs and L4S: Label DSCP

"C. M. Heard" <heard@pobox.com> Tue, 01 June 2021 17:35 UTC

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From: "C. M. Heard" <heard@pobox.com>
Date: Tue, 01 Jun 2021 10:35:25 -0700
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To: "Black, David" <David.Black@dell.com>
Cc: TSVWG <tsvwg@ietf.org>
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Subject: Re: [tsvwg] DSCPs and L4S: Label DSCP
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On Fri, May 28, 2021 at 3:02 PM Black, David <David.Black@dell.com> wrote:

> This note proposes a simple usage of DSCPs with L4S, hereafter called
> "Label DSCP". This is a proposal for the WG to consider, adopt, reject,
> fold, spindle and/or mutilate as the WG sees fit. This note is not
> direction to the WG from a WG chair.  The Label DSCP proposal is based on
> Section 3 of RFC 4774, which assumes (but does not require) use of DSCPs to
> indicate alternate ECN semantics:
>
[ ... ]

>               B. Transport protocols do not react to receipt of specific
>
>                             DSCPs from the network. DSCPs on end systems
> continue
>
>                             to function as inputs to the network, not as
> outputs
>
>                             from the network.
>

What I don't understand is how this proposal prevents an L4S sender from
competing unfairly with classic traffic when traversing a non-participating
domain.

Doesn't the sender need feedback from the receiver that the label DSCP was
received? And the the the receiver is itself capable of providing the type
of CE feedback that the L4S send needs?

Sorry if I am being obtuse. It would not be the first time :-(

Mike Heard

>

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