I still don't see any value in adding text like this. The description of the tree walk is clear enough.

On Wed, 3 Aug 2022, Alessandro Vesely wrote:

On Tue 02/Aug/2022 14:33:21 +0200 Barry Leiba wrote:
I think it is useful to include a brief explanation of why we moved away
from the PSL, because that was in the previous version.  But we should
be very tightly focused when we give any such background, to avoid
creating distractions.


Here's one more attempt at proposing the text of a complete, free-standing section:

   There is no general rule to determine domain prefixes.  The PSL is the
   result of the ongoing, ponderous work of a group of volunteers who
   examine each case.  However, DMARC users define DMARC records at their
   Organizational Domain, so it is possible to discover them based on
   that.  Here we define an algorithm that determines the Organizational
   Domain for DMARC purposes.  For established prefixes, the result is the
   same as using the PSL.

   Given a  DNS Tree Walk (#dns-tree-walk) which retrieved at least one
   DMARC record, determine the Organizational Domain by applying the
   following rules, from the longest domain toward the shortest one:

  1.  If a valid DMARC record contains the psd= tag set to 'n' (psd=n),
      this is the Organizational Domain and the selection process is
      complete.

  2.  If a valid DMARC record, other than the one for the domain where
      the tree walk started, contains the psd= tag set to 'y' (psd=y),
      the Organizational Domain is the domain one label below this one
      in the DNS hierarchy, and the selection process is complete.

  3.  Otherwise select the record for the domain with the fewest number
      of labels.  This is the Organizational Domain and the selection
      process is complete.


Best
Ale


Regards,
John Levine, [email protected], Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly

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