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

"Murray S. Kucherawy" <superuser@gmail.com> Tue, 24 November 2020 16:50 UTC

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From: "Murray S. Kucherawy" <superuser@gmail.com>
Date: Tue, 24 Nov 2020 08:50:20 -0800
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To: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [dmarc-ietf] Doing a tree walk rather than PSL lookup
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On Tue, Nov 24, 2020 at 4:20 AM Alessandro Vesely <vesely@tana.it> wrote:

> > 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.
>
> The PSL processing is a local lookup on an in-memory suffix tree.  How is
> it a
> progress to replace it with a tree walk?  A PSL search is lightning faster
> than
> even a single DNS lookup, isn't it?
>

Sure, but only if you think the PSL is accurate.  Otherwise you're basing
your shortcut up the tree on data you don't have reason to trust.  On the
other hand, a tree walk, while more expensive in terms of queries, isn't a
heuristic based on possibly stale information.

-MSK

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