[tsvwg] Scope of the L4S Experiment (was: Guard DSCP)

["C. M. Heard" <[e-mail]>]

On Tue, Apr 27, 2021 at 3:57 PM Black, David wrote:

> the appropriate L4S experiment scope may be sets of
> cooperating/participating networks rather than the (originally envisioned)
> Internet as a whole.
>

I had certainly understood the intended scope to be sets of
cooperating/participating networks rather than the Internet as a whole. How
could it possibly be otherwise, with a change in the semantics of CE that
is incompatible with existing standards, without at the same time
obsoleting those standards?

When Differentiated Services was introduced by RFC 2474, the existing TOS
standard was obsoleted, based on good evidence that it was unused (there
was only one implementation of TOS routing, IIRC, and negligible
deployment). It didn't get introduced as an experiment.

When the original experimental incarnation of ECN was specified by RFC
2481, it could be introduced as an internet-wide experiment because prior
standardized uses of the field had been obsoleted on good evidence of
non-use, and there was good evidence that harm would not be caused to
deployed systems.

The evidence presented here strongly suggests to me that L4S is not benign
to existing standards. If it is to be used experimentally, it must be
contained. If it is to be used internet-wide, then existing incompatible
uses should be obsoleted.

One or the other, please. Don't deploy L4S internet-wide and call it
experimental.

Mike Heard

>