Subject: Re: [dmarc-ietf] Comment on draft-ietf-dmarc-psd

From: "Murray S. Kucherawy" <[email-masked]>
Date: Fri, 17 Jan 2020 00:06:11 -0800

On Mon, Dec 9, 2019 at 8:44 AM Dave Crocker <[email-masked]> wrote:

> The IETF does not typically -- or, as far as I recall, ever -- promote
> specifications known not to scale.  (While I think of this concern as
> foundational to the IETF, it's a bit odd that nothing like it is

included in the IETF's "Mission and principles" statement.[1])

I'm not sure that I would reasonably expect anything labeled "Experimental"
to scale, especially if it were to make very explicit claims to the
contrary.  Nothing I've worked on at the IETF with such a label is
something I would necessarily stand behind as Internet-scalable.  But I
would probably expect something at Informational probably to scale, and
anything with "Standard" in it certainly to scale.

> > Comparing it to the "obs" grammars of days of yore, the PSD proposal
> > is much too expensive to become engrained as-is, whereas the old
> > grammars were relatively easy to carry forward.
>
> I don't quite grok the reference to "obs", and mostly think of the
> introduction of that construct in RFC 2822 as an interesting idea that,
> itself, failed.  (I see it as being instructive on the challenges of
> designing for transition from an installed base.)
>

That was indeed the intended reference.

All sorts of experimental specs fail.  But they aren't /expected/ to
> fail.  And they aren't expected to be unable to scale.
>

This one isn't expected to fail, but its mechanism is not (as far as I can
tell) intended to be permanent, nor could it become so.  In terms of
meeting its stated goal, we don't know the outcome yet.  We have a guess,
but we need data to confirm it, and everyone participating needs to agree
on how to participate.  That seems to me to be what an Experimental
specification is for.  The non-scalable component is part of the means by
which participants agree on the operation of the test itself.

Mostly, IETF/Experimental is used to check whether a spec is
> operationally viable -- it's expected to be but the community isn't
> quite sure -- or to check for community interest.  The latter
> constitutes market research, not technical research.
>

I would claim it's clear that this is the former.  We're trying to assess
whether this extended logic is a reasonable change to the accuracy of
DMARC.  Some of the supporting mechanism added in the experiment is
ancillary to that goal, and is discardable.  Nothing to do with market
research.

A pointedly friendly reading of the relevant Guidelines might seem to
> support the publication under IETF/Experimental being proposed here, but
> a more critical one probably doesn't and I think that this use of the
> label doesn't really match common practice.[2]
>

The status chosen most closely reflects the intent and quality of the work,
certainly as compared to something aiming for the standards track.  And
there's consensus to move forward, or was when WGLC ended.  Quite a bit of
time has now passed since then and we are no closer to getting the answers
the working group needs to make progress on the core issues it's facing.
Rightly, there's now a lot of grumbling going on.

Since one of your core assertions is that the IETF shouldn't publish things
like this, I have suggested that, as a compromise, interested parties
proceed with the experiment using the document in its draft state.
Unfortunately I am also regularly reminded that there are organizations
wishing to participate in this experiment and related work but which simply
cannot, by reason of policy, do so without this document being first
approved for publication.  I personally find that position peculiar -- many
things from DKIM up to QUIC are implemented experimentally by very large
operators during development, without an approved document -- and it's not
really the IETF's responsibility to acquiesce, but nevertheless it results
in some urgency for this community to find a way forward here.

So: Can you propose any sort of specific restructuring of the document or
the experiment that achieves the same goal as the current version while
also resolving your concerns?

The real challenge for most IETF specs is community engagement, not
> engineering adequacy.

Interestingly I would claim we have clearly achieved the former here,
though obviously not the latter.

Also, any suggestion to rely on a published list ignores the history of
> problems with such lists, as well as at least requiring a careful
> specification for the list and a basis for believing it will be
> maintained well.
>

The list, as I understand its use in the specification, amounts to a list
of who's participating in the experiment.  When the experiment is done, the
list goes away, and the concerns of its maintenance would go with it.

-MSK

---

From: Dave Crocker <[email-masked]>
Date: Fri, 17 Jan 2020 08:44:25 -0800

On 1/17/2020 12:06 AM, Murray S. Kucherawy wrote:
> On Mon, Dec 9, 2019 at 8:44 AM Dave Crocker <[email-masked] 
> <mailto:[email-masked]>> wrote:
>
> I'm not sure that I would reasonably expect anything labeled 
> "Experimental" to scale, especially if it were to make very explicit 
> claims to the contrary.

As a standalone bit of thinking that sounds reasonable, but it does not 
match my sense of IETF history, nor my sense of application of that 
model in the case of X-.  What you describe makes sense for something 
out of the IRTF, not IETF.

As for IETF history, while there certainly have been IETF Experimental 
RFCs that have failed, I don't recall their being /expected/ to fail.  
(I'm counting inability to scale as failure. If anyone has a different 
view of inability to scale, there needs to be a separate discussion...)

For the latter:  X- was an email header field construct design to make 
an explicit statement that something was /not/ a standard header field. 
I was added to the RFC 822 spec, though I do not remember who first 
suggested it, other than it wasn't me.  I thought it a fine and 
reasonable idea, as did many others.  Note that it was eventually 
deprecated. Because it did not work as intended:  People using X- fields 
came to rely on them, creating defacto standards.

That's the danger with an IETF stream RFC, especially one coming out of 
a working group: Those implementing and using an IETF published 
specification tend to come to rely on continuing to use it.

> Nothing I've worked on at the IETF with such a label is something I 
> would necessarily stand behind as Internet-scalable.

Such as?

> But I would probably expect something at Informational probably to 
> scale, and anything with "Standard" in it certainly to scale.

Laying any general expectation on an IETF Informational RFC would be a 
mistake, because there is so much variety in their content and intent.

> That was indeed the intended reference.

I don't understand how you see benefit in citing a reasonable idea that 
failed -- obs- did not serve its intended purpose and was in a standards 
track specification: The obs- rules both weren't deprecated from later 
work and continue to be relied on. If anything, it validates my concern 
about entrenched use.

> This one isn't expected to fail,

If it is known that it can't scale, that's inherent failure for IETF work.

> but its mechanism is not (as far as I can tell) intended to be 
> permanent, nor could it become so.

You keep making statements that warrant this as IRTF work, not IETF work.

> Since one of your core assertions is that the IETF shouldn't publish 
> things like this, I have suggested that, as a compromise, interested 
> parties proceed with the experiment using the document in its draft 
> state.

Sounds like a fine idea, to me.

> Unfortunately I am also regularly reminded that there are 
> organizations wishing to participate in this experiment and related 
> work but which simply cannot, by reason of policy, do so without this 
> document being first approved for publication.

That should raise some very bold, very large red flags about publishing 
this as an IETF stream RFC.

> So: Can you propose any sort of specific restructuring of the document 
> or the experiment that achieves the same goal as the current version 
> while also resolving your concerns?

I'm pretty sure I've raised fundamental concerns about this work and 
that those concerns have not been addressed.  The simple summary is that 
the way to restructure this work is to go back to first principles.  But 
there doesn't seem to be any interest in having that sort of discussion.

> though obviously not the latter.

My sense is -- as has become common in the IETF -- an extremely small 
core of folk interesting in promoting this work, rather than extensive 
community interest.

Extensive community interest is what generates serious demonstration of 
utility at scale.

d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net