Subject: Re: [DNSOP] I-D ACTION:draft-licanhuang-dnsop-distributeddns-04.txt

From: Dean Anderson <[email-masked]>
Date: Sun, 6 Jul 2008 18:16:29 -0400 (EDT)

Oh yeah--That's right. 32 levels--Much worse than I said.  I wrote up
many of the issues with reverse dns about 1.5 years ago. I submitted it
to the IETF, but there was no interest in publishing this information.

http://www.av8.net/draft-anderson-reverse-dns-status-01.txt

The following example was taken from RFC3596:

    4321:0:1:2:3:4:567:89ab

   would be

    b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.4.IP6.
                                                                   ARPA.

On Mon, 30 Jun 2008, Frederico A C Neves wrote:

> Mr. Anderson,
> 
> On Sat, Jun 28, 2008 at 05:36:04PM -0400, Dean Anderson wrote:
> > A number of the points you raise have already been addressed.
> > 
> > The IPV6 Reverse resolution question has been discussed at length in
> > DNSEXT previously. In fact, it was proposed to remove reverse resolution
> > entirely from IPV6 for just the reason Dr. Huang notes.  A 128 bit IPV6
> > address is 16 octets. To perform reverse resolution requires traversing
> > 16 levels of DNS tree. 
> 
> Not exactly. The reverse delegation is at the 4 bits boundary, so the
> correct is 32 possible levels, but this possibility doesn't impose all
> these levels. Half of the levels are unlikely to be used and the other
> half you'll see normally the average of 3 to 4 as we see it today for
> IPv4. The amount of delegations levels are driven by the IP
> distributions layers (IANA-RIR-NIR-ISP), not by the address space.
> 
> Fred
> _______________________________________________
> DNSOP mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/dnsop
> 
> 

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---

From: Dean Anderson <[email-masked]>
Date: Sun, 6 Jul 2008 18:16:29 -0400 (EDT)

4321:0:1:2:3:4:567:89ab

   would be

---

From: Joe Abley <[email-masked]>
Date: Sun, 6 Jul 2008 19:02:34 -0400

On 6 Jul 2008, at 18:16, Dean Anderson wrote:

> Oh yeah--That's right. 32 levels--Much worse than I said.

No. To reiterate the point that I saw Fred making...

>  I wrote up
>    b.a. 
> 9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.4.IP6.
>                                                                    
> ARPA.

... such a PTR record would most likely be obtained by following four  
(root -> ip6.arpa -> RIR sever -> LIR server -> assignee server) or  
three (root -> ip6.arpa -> RIR server -> assignee server) delegations.  
I doubt this is substantially different, in aggregate, from IPv4.

You seem to be confusing label boundaries with zone cuts in your  
"analysis".

Joe

---

From: Joe Abley <[email-masked]>
Date: Sun, 6 Jul 2008 19:02:34 -0400

Joe

---

From: Florian Weimer <[email-masked]>
Date: Tue, 08 Jul 2008 10:09:11 +0200

> I doubt this is substantially different, in aggregate, from IPv4.

It's actually better with IPv6 than with IPv4 because the LIR aggregate
is at a multiple-of-4 boundary, so there's no need to delegate multiple
zones for one address block, and it's also more likely that the RIR ->
LIR delegation has been cached by the resolver.
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---

From: Florian Weimer <[email-masked]>
Date: Tue, 08 Jul 2008 10:09:11 +0200

---

From: Dean Anderson <[email-masked]>
Date: Tue, 8 Jul 2008 22:24:17 -0400 (EDT)

I'm not confusing zone boundardies with label boundaries. 32 levels is
the worst case.  In practice, it'll probably be much more than 3 or 4
levels, but probably in most cases fewer than 32.  But it is widely
expected to be very problematic to maintain, and has always been
problematic to maintain, even in IPv4. Hence the efforts on
RFC1788(IPv4) and RFC4620(IPv6)

		--Dean

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6From [email-masked]  Tue Jul  8 19:24:32 2008
Date: Tue, 8 Jul 2008 22:24:17 -0400 (EDT)
From: Dean Anderson <[email-masked]>
To: Joe Abley <[email-masked]>
Cc: [email-masked]
Subject: Re: [DNSOP] I-D ACTION:draft-licanhuang-dnsop-distributeddns-04.txt
Sender: [email-masked]

I'm not confusing zone boundardies with label boundaries. 32 levels is
the worst case.  In practice, it'll probably be much more than 3 or 4
levels, but probably in most cases fewer than 32.  But it is widely
expected to be very problematic to maintain, and has always been
problematic to maintain, even in IPv4. Hence the efforts on
RFC1788(IPv4) and RFC4620(IPv6)

		--Dean

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