Re: [dmarc-ietf] Concerns about Oldest-Pass (was: Last Call: <draft-ietf-dmarc-arc-protocol-18.txt>...)

"Kurt Andersen (b)" <kboth@drkurt.com> Mon, 05 November 2018 06:32 UTC

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From: "Kurt Andersen (b)" <kboth@drkurt.com>
Date: Mon, 5 Nov 2018 13:31:50 +0700
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To: Scott Kitterman <sklist@kitterman.com>, Bron Gondwana <brong@fastmailteam.com>
Cc: "dmarc@ietf.org" <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] Concerns about Oldest-Pass (was: Last Call: <draft-ietf-dmarc-arc-protocol-18.txt>...)
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Explicitly looping in that one person to see if his thoughts have changed
over time.

--Kurt

On Mon, Nov 5, 2018 at 12:25 PM Scott Kitterman <sklist@kitterman.com>
wrote:

> I don't think it's something we should delay on.  In my, admittedly
> limited,
> experience with these things, once something is in an experimental version
> of
> an RFC, then it 'has' to be preserved in the name of interoperability with
> the
> installed base.  I think now is the time to remove obvious fluff.  This
> documents makes my head hurt enough as it is.
>
> If anything, it should be a separate document as it's got nothing to do
> with
> ARC, per se.  Any utility of AMS past the immediate previous one is
> entirely
> speculative.  Let's lean towards easy, not hard.  Now is the time to prune
> this.
>
> Having reviewed the thread that Kurt pointed me to, it seemed like this is
> something only one person wanted.  It didn't appear to have a lot of push
> behind it.
>
> Scott K
>
> On Monday, November 05, 2018 01:54:33 PM Murray S. Kucherawy wrote:
> > Given the intended status is Experimental, is this something that's a
> > showstopper?
> >
> > We have the debate about "fail" versus "invalid" that I believe we
> consider
> > to be a showstopper for Proposed Standard, but we're willing to let slide
> > for Experimental.  Is this the same?
> >
> > -MSK
> >
> > On Mon, Nov 5, 2018 at 1:13 PM Scott Kitterman <sklist@kitterman.com>
> wrote:
> > > On November 5, 2018 3:35:23 AM UTC, Kurt Andersen <kurta@drkurt.com>
> > >
> > > wrote:
> > > >Taking this back to the dmarc list instead of the IETF-wide one:
> > > >
> > > >On Wed, Oct 31, 2018 at 1:41 AM Scott Kitterman <scott@kitterman.com>
> > > >
> > > >wrote:
> > > >> . . .  I understand the desire to just ship it at this point so more
> > > >> operational experience can be gained before another update.  With
> one
> > > >> exception, I agree with that approach.
> > > >>
> > > >> In Section 5.2.  Validator Actions, I think it's highly unlikely
> that
> > > >
> > > >Step
> > > >
> > > >> 5, AMS (ARC Message Structure) validation of AMS header fields
> beyond
> > > >
> > > >the
> > > >
> > > >> one immediately prior in the chain is useful.
> > > >>
> > > >> Failure doesn't change the ARC result, so there are no
> > > >
> > > >interoperability
> > > >
> > > >> implications for removing it from the draft.  The only reason to
> > > >
> > > >specify
> > > >
> > > >> anything is the notion of 'oldest-pass'.  This looks like a dubious
> > > >
> > > >and
> > > >
> > > >> premature optimization to me.
> > > >>
> > > >> I didn't and don't plan to implement it.
> > > >>
> > > >> Later, after there is more experience with ARC, if it's established
> > > >
> > > >that
> > > >
> > > >> validation of AMS beyond the immediately prior step in the chain has
> > > >> utility and there is sufficient efficiency associated with
> > > >
> > > >'oldest-pass',
> > > >
> > > >> it can be added then.  'Oldest-pass' seems like an easy way to get
> > > >
> > > >around
> > > >
> > > >> having downstream validators do AMS validation up the chain (by
> > > >
> > > >always
> > > >
> > > >> adding arc.oldest-pass=1 to all messages).
> > > >>
> > > >> ARC is complicated enough without this and it seems like any easy
> win
> > > >
> > > >for
> > > >
> > > >> simplicity in design to take this out for now (and we'll see about
> > > >
> > > >the
> > > >
> > > >> future).  Deleting it also reduces the IANA considerations.
> > > >
> > > >I'm not by any means arguing with your analysis and plans to skip this
> > > >component, but I did want to point you, for informational purposes to
> > > >the
> > > >WG thread which was the genesis of this concept. It was originally
> > > >proposed
> > > >as "closest-fail" but then inverted to be "oldest-pass". You can find
> > > >the
> > > >thread from January 2018 at
> > > >
> https://mailarchive.ietf.org/arch/msg/dmarc/_sG6ECCBfT5OPQ0LkDThzcGPHGI
> > > >which references an older discussion circa August 2017.
> > >
> > > Thanks.  I've reviewed it and my opinion is reinforced.  It ought to be
> > > removed.  Nothing other than the immediate prior AMS matters for
> > > evaluation
> > > of the ARC result.  Everything about prior hops is purely for receiver
> > > edification, not needed for the protocol.
> > >
> > > Scott K
> > >
> > > _______________________________________________
> > > dmarc mailing list
> > > dmarc@ietf.org
> > > https://www.ietf.org/mailman/listinfo/dmarc
>
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