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Re: [dmarc-ietf] Doing a tree walk rather than PSL lookup

John Levine <johnl@taugh.com> Mon, 23 November 2020 21:38 UTC

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From: John Levine <johnl@taugh.com>
To: dmarc@ietf.org
Cc: dcrocker@gmail.com
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Subject: Re: [dmarc-ietf] Doing a tree walk rather than PSL lookup
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In article <9f388e33-c15d-9fcc-e9d3-d7719288fb98@gmail.com> you write:
>On 11/23/2020 1:04 PM, Jesse Thompson wrote:
>> I meant to suggest that the requirement for a tree walk would be that the Organizational Domain would need to have that in its policy. 
>It seems like a decent compromise for the people worried about unnecessary DNS lookup overhead.

If I'm going to go to the effort to download and decode a PSL and find the OD, I'll just use the OD.

One of the points of the tree walk is to get rid of the PSL processing.

It looks to me that a tree walk limited to some modest number of
levels like 7 or 10 would handle close enough to 100% of real mail.
When I brought this up in dnsop last week there was some concern about
super long tree walks but I didn't get the NO NO NO that we got in the
old days. DNS operators now realize that an amazingly large fraction
of DNS traffic is garbage, and a little extra noise from the
occasional tree walk is not a big deal.

In normal mail, the number of labels is usually quite low, here's my distribution by
number of dots:

2404 .
1215 ..
 152 ...
  10 ....

R's,
John

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