non-improving referral

[tale]

On Mon, Jul 5, 2021 at 8:20 PM Mark Andrews <marka at isc.org> wrote:
> This is an error with the delegation of ok.contact.  The NS records at the delegation point do
> not match those at the zone apex.

I'm curious if this is a re-purposing of the existing "non-improving
referral" message.  I totally get how that brief phrase makes sense
for a sideways referral, but I'm not seeing how that statement makes
sense for ok.contact.

# Delegation for .contact
$ dig +noall +auth ns contact @a.root-servers.net
contact. 172800 IN NS demand.beta.aridns.net.au.
contact. 172800 IN NS demand.alpha.aridns.net.au.
contact. 172800 IN NS demand.delta.aridns.net.au.
contact. 172800 IN NS demand.gamma.aridns.net.au.

# Delegation for ok.contact
$ dig +noall +auth ns ok.contact @demand.alpha.aridns.net.au.
ok.contact. 86400 IN NS fwd2.dccdns.com.
ok.contact. 86400 IN NS fwd1.dccdns.com.
ok.contact. 86400 IN NS fwd4.dccdns.com.
ok.contact. 86400 IN NS fwd3.dccdns.com.

# Apex NS for ok.contact
$ dig +noall +ans ns ok.contact @fwd1.dccdns.com
ok.contact. 3499 IN NS fwd4.dns.ws.
ok.contact. 3499 IN NS fwd2.dns.ws.
ok.contact. 3499 IN NS fwd1.dns.ws.
ok.contact. 3499 IN NS fwd3.dns.ws.

Yes, the apex NS names aren't the same as the delegating NS (though
the adb addresses are), but that last one isn't a referral.

I trust you are right, Mark.  I'm just not sure what I'm missing about
"non-improving referral".
-- 
tale