[DNSOP] Using the SOA in a NXDOMAIN response (Was: [internet-drafts@ietf.org: I-D Action: draft-bortzmeyer-dnsop-nxdomain-cut-00.txt]

Stephane Bortzmeyer <bortzmeyer@nic.fr> Fri, 13 November 2015 19:53 UTC

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Date: Fri, 13 Nov 2015 20:50:15 +0100
From: Stephane Bortzmeyer <bortzmeyer@nic.fr>
To: "Wessels, Duane" <dwessels@verisign.com>
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References: <20151106082238.GA2307@nic.fr> <A62EC834-C954-446C-9F7A-AB6D1F955C7F@verisign.com> <20151112081514.GA16017@laperouse.bortzmeyer.org> <39D878B4-9239-4983-8083-36BCA365BE62@verisign.com>
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Subject: [DNSOP] Using the SOA in a NXDOMAIN response (Was: [internet-drafts@ietf.org: I-D Action: draft-bortzmeyer-dnsop-nxdomain-cut-00.txt]
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On Thu, Nov 12, 2015 at 06:13:04PM +0000,
 Wessels, Duane <dwessels@verisign.com> wrote 
 a message of 57 lines which said:

> As Mark pointed out, we can't use the SOA to make NXDOMAIN more aggressive.
> For a name like foo.bar.example.com and an NXDOMAIN response from
> example.com we can't assume that there would be a zone cut between
> foo and bar.

Could anyone explain in detail why is it so? [I don't understand why
the zone cut is important here: using the SOA does not depend on
whether there is a zone cut or not.]

Let's say I query foo.bar.example to example's name servers. I get:

;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 64182
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 8, ADDITIONAL: 1
;foo.bar.example.		IN SOA

example.			5400 IN	SOA nsmaster.nic.example. hostmaster.nic.example. (
				2222956935 ; serial
				3600       ; refresh (1 hour)

It can mean only one thing, that bar.example does not exist. How could
it be different?