Re: [tsvwg] draft-white-tsvwg-l4sops-02.txt proposa for additional sections

[Ingemar Johansson S <[e-mail]>]

Hi Sebastian..
Unfortunately the proposed section 6.2 sounds a lot like the famous Mission
Impossible one-liner "This tape will self-destruct in five seconds. Good
luck, Jim."
The ECN Nonce was experimental and was recently declared historic a few
years ago, literary speaking RFC3540 did not self destruct, it just faded
away. I don't see anywhere in RFC3540 about what end hosts and networks
should do when RFC3540 is declared historic. And I guess that the way
forward, in case the whole L4S experiment falls flat, is that the L4S ID RFC
is declared historic, I guess this should be enough.
But lets imagine that detailed information is needed to address the case
that L4S fails. This leads to the question. 
Are there any other examples in IETF's history where an experimental RFC has
been accompanied with a detailed instruction on how to clean up after the
experiment ?

/Ingemar 

> -----Original Message-----
> From: tsvwg <[e-mail]> On Behalf Of Sebastian Moeller
> Sent: den 16 april 2021 22:57
> To: tsvwg IETF list <[e-mail]>; Greg White <[e-mail]>
> Subject: [tsvwg] draft-white-tsvwg-l4sops-02.txt proposa for additional
> sections
> 
> Hi Greg, hi list,
> 
> I think that the L4S ops draft could be improved by saying something
explicit
> about the end of the L4S experiment and what differential actions are
> recommended for participants at that point in time. I made this argument
> already at the end of
> https://mailarchive.ietf.org/arch/msg/tsvwg/NXEACkPX1pFriOtqsoifPzoI8Sk/
> but I believe that it might have been overlooked there at the end of a
long
> email.
> 
> So, here is my proposal to that regard as a new section 6:
> 
> 
> 6. What L4S-deploying networks should to do at the end of the L4S
> experiment
> 
> This section gives guidance how L4S-deploying networks should respond to
> any of the two possible outcomes of the IETF-supported L4S experiment.
> 
> [COMMENT: I believe that there needs to be a proper definition how the L4S
> experiment is supposed to be evaluated at the end to decide between
> success and failure, but the L4S-ops document seems to be the wrong place
> for that, so I propose to add this to one of the L4S core IDs, preferably
to
> section 6 of https://datatracker.ietf.org/doc/draft-ietf-tsvwg-ecn-l4s-id/
> which already contains discussion about what the experiment is supposed to
> figure out, so adding a section how to evaluate the outcome there seems a
> natural fit; IMHO the deciding factor here could be whether L4S is
promoted
> to proposed standard status after the experiment, if and only if that
happens
> L4S should be considered a success... I base this on the already known
> problematic side-effects of L4S and the fact that L4S will consume a
rather
> scarce resource in an IP-level code-point the exists in both IPv4 and
IPv6,
> which IMHO should be released ASAP if L4S fails to succeed]
> 
> 6.1 Successful termination of the L4S experiment
> 
> If the L4S experiment is deemed successful, participating networks are
> encouraged to continue deploying L4S-aware nodes and if possible replace
all
> non-L4S-aware rfc3168 AQM already deployed as far as feasible, or at least
> restrict rfc3168 AQM to interpret ECT(1) equal to NotECT. Participants are
also
> expected to track the evolution of the L4S standards and adapt their
> implementations accordingly (e.g. if as part of switching from
experimental
> to standards track, changes in the L4S RFCs become necessary).
> 
> 
> 6.2 Unsuccesful termination of the L4S experiment
> 
> If the L4S experiment is deemed unsuccessful, it might need to be
> terminated: L4S network nodes should be un-deployed and the ECT(1)
> codepoint usage should be released/recycled quickly.
> 	To achieve the former, participants of the L4S experiment are
> expected to configure their L4S-aware network nodes such that either the
> LL-queue of a dual queue AQM gets completely disabled, or that the LL-
> queue is switched from issuing CE-marks to pure drops; thereby removing
> L4S-signaling from the network. To achieve the latter, all endpoint hosts
> need to stop negotiating L4S-congestion signaling. For nodes under control
of
> participating networks that should only require re-configuration of the
> endpoint hosts. For nodes not under control of participants of the
> experiment that will be a considerable challenge. To give a strong signal
to
> such out-of-network endpoints drastic measures might be required, like re-
> marking ECT(1) packets to NotECT or even dropping all ECT(1) packets on
> network ingress, as these will give clear and strong incentives to
endpoints to
> stop using ECT(1)/L4S-signaling. But to avoid "burning" the ECT(1)
codepoint
> indefinitely, such measures should be restricted to a limited duration
(e.g. 24
> month) after an unsuccessful termination of the L4S experiment, to allow
the
> ECT(1) codepoint to be recycled for other uses/experiments afterwards.
> 
> 
> 
> I am sure that this is not going to be complete and that there will be
differing
> opinions on these sections, but I believe something similar in scope
should
> be added.
> 
> Best Regards
> 	Sebastian