Subject: Re: qtype addr scorecard

From: Markku Savela <[email-masked]>
Date: Wed, 21 Aug 2002 21:25:07 +0300

> From: Paul Vixie <[email-masked]>

> > Instead of additional section, why not my other proposal: return IPv4
> > addresses in AAAA query as IPv6 addresses (ipv4 mapped format).
> 
> Synthetic data is very touchy.  Those mapped AAAA's would have to have TTL=0,
> for example, which would mean the whole AAAA RRset would be minimized to TTL
> 0.  I don't think this situation calls for synthetic data.

I was not proposing "synthetic data". What I proposed, can be
simulated manually using current name servers without any change as
follows:

  - when you enter A record for address 1.2.3.4, you also enter AAAA
    record for ::ffff:1.2.3.4

It would be a convenience feature, if some new version of server did
this implicitly.

However, I did not suggest that some intermediate server should do any
merging of AAAA query with A queries.

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From: Rob Austein <[email-masked]>
Date: Wed, 21 Aug 2002 15:26:35 -0400

At Wed, 21 Aug 2002 21:25:07 +0300, Markku Savela wrote:
> simulated manually using current name servers without any change...

Right.  The difficulties I see  with the mapped approach are that:

a) By adding v4 addresses to the AAAA RRset, it makes the AAAA RRset
   bigger and leaves you with no way to say that you just want the
   IPv6 addresses.  That is, it has a mild flavor of the subtyping
   problem, although I will admit that IP addresses are so close to
   being the same thing as IP addresses that maybe it doesn't matter.

b) The case where a dual-stack machine is most likely to want the IPV4
   addresess is, unfortunately, also the case that's most likely not
   to have bothered supplying the mapped addresses at all.  That is,
   while you'd get some benefit from the ability to supply the mapped
   addresses for a host that's IPv6-aware but IPv4-only, the case on
   which you'd really like to get some traction is the one that's not
   playing here (IPv4 only and doesn't care about IPv6).

Neither of these issues is necessarily a showstopper.  John Klensin
and I discussed something very close to this a couple of years ago and
I still kind of like the idea.

In the final analysis, though, what I mostly care about is coming up
with the simplest set of rules that gets everybody the right answer in
every case where a right answer is possible.  So while I'm happy to
discuss other options, I still tend towards the idea that the
application should just ask for the RRsets it needs, one RRset at a
time, and let the caching take care of itself.

---

From: [email-masked]
Date: Thu, 22 Aug 2002 07:44:05 +0900

>It would be a convenience feature, if some new version of server did

	no IPv4 mapped address on wire, ever, please.  i'm writing up a
	draft why it is harmful.  it is very, very, harmful.

itojun