Re: [dmarc-ietf] Ruminating the tree walk

[Scott Kitterman <[e-mail]>]

On Wednesday, March 23, 2022 6:59:08 AM EDT Alessandro Vesely wrote:
> Hm...
> 
> On Wed 23/Mar/2022 03:08:35 +0100 Douglas Foster wrote:
> > During my ruminations last night, I gained some clarity around that
> > question and wanted to highlight those conclusions.  They simplify the
> > alignment search significantly:
> > 
> > - If the common substring is shorter than the Organizational Domain, then
> > the names are not aligned and the candidate domain can be ignored.
> > 
> > - Otherwise, if any candidate domain is a parent of (or equal to) the FROM
> > domain, then and we have alignment and DMARC PASS.  The secondary tree
> > walk is not needed and no further evaluation is required.
> > 
> > - If several candidate names are child domains of the FROM address, then
> > only the shortest string needs to be evaluated with a secondary tree
> > walk.  If it is aligned, further evaluation is not required.  If it is
> > not aligned because of an organizational boundary, all other child
> > domains are also excluded.
> That and the deeper-than-5 optimization Doug posted on a separate message.
> 
> 
> I know the document is already longish.  However, collecting these
> observations in an appendix may be helpful for developers, and maybe also
> for general understanding of the intricacies involved in the tree walk,
> including proper usage of the psd= flag.

I think we do need to add some additional clarity, which I plan to draft, but 
let's not go overboard.  We are trying to describe a protocol, not a 
implementation specification.  So far, in my experience, the extra code 
required to address short cuts like this is not justified by the improved 
'efficiency'.  I don't think these need to be in the document.

Scott K