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

Alessandro Vesely <> Tue, 24 November 2020 12:20 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id C97E53A09DA for <>; Tue, 24 Nov 2020 04:20:00 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -0.221
X-Spam-Status: No, score=-0.221 tagged_above=-999 required=5 tests=[DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1152-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id QNABZE-QwCzS for <>; Tue, 24 Nov 2020 04:19:59 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 2A32C3A09D3 for <>; Tue, 24 Nov 2020 04:19:58 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=delta; t=1606220394; bh=W48jF7itlL5KNQbKXEYZU1TJ78Fxz1S3ID9r4ch9VUM=; l=820; h=To:References:From:Date:In-Reply-To; b=A+e9I1E3Cc0n7Z1cZ4jcFlFuipjOjlUnn/m8GiLVqT4sSaT83XLqDzWf6t2b8D1zT nG5FwV1nm/Epbbd6LHjhmuRlVXBaZFj05PHI8ZyVSFhI8CPbTurgsrjzZ5d25ECGrQ vr7c0CmOKbvi4uVrcjWzX0KwO8YvVwsO5oPQ2cCMCxzP86O+fI03parI7lIzQ
Authentication-Results:; auth=pass (details omitted)
Original-From: Alessandro Vesely <>
Received: from [] (pcale.tana []) (AUTH: CRAM-MD5 uXDGrn@SYT0/k, TLS: TLS1.3, 128bits, ECDHE_RSA_AES_128_GCM_SHA256) by with ESMTPSA id 00000000005DC081.000000005FBCFA6A.0000614A; Tue, 24 Nov 2020 13:19:54 +0100
References: <20201123213846.EB14127C8160@ary.qy>
From: Alessandro Vesely <>
Message-ID: <>
Date: Tue, 24 Nov 2020 13:19:54 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0
MIME-Version: 1.0
In-Reply-To: <20201123213846.EB14127C8160@ary.qy>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: <>
Subject: Re: [dmarc-ietf] Doing a tree walk rather than PSL lookup
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Domain-based Message Authentication, Reporting, and Compliance \(DMARC\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 24 Nov 2020 12:20:01 -0000

On Mon 23/Nov/2020 22:38:46 +0100 John Levine wrote:
> In article <> 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.

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?