Re: [BEHAVE] draft-boucadair-behave-dns-a64-00.txt [was RE: I-D Action:draft-ietf-behave-dns64-01.txt]

[<eric.burgey at orange-ftgroup.com>]

Hello Dan,
I hope that the answer to your question is more clear in the new version of the draft:  "draft-boucadair-behave-dns-a64-01.txt"

Just to summarize:
Querying an existing DNS64 with CD and DO bits set is just a specific request, but as we explain at the end of section 3.1 it is not enough. We need a specific record type to manage static entries in DNS pointing to IPv4-mapped-IPv6 addresses.
Such case append when NAT64 is used to interconnect IPv6 internet to an IPv4 network.
As explain in section A.4 of "draft-ietf-behave-dns64-01" the best way to address this scenario is to built a static entry in the authoritative DNS server with an IPv4-mapped-IPv6 address built with the Pref64::/n used by the operator of this domain. But if an AAAA record is used for this record a dual-stack host would prefer this AAAA records compared to the A record and all communications will pass through the NAT64 and may experience trouble with the ALG mechanisms.
An A64 records is just like an AAAA records but with a priority lower than a A records for a dual-stack host. An A64 records may be used in an Authoritative server and is not necessarily synthesized by the local DNS resolver.

Bets regards

	Eric BURGEY


-----Message d'origine-----
De : Dan Wing [mailto:dwing at cisco.com] 
Envoyé : jeudi 22 octobre 2009 19:09
À : BOUCADAIR Mohamed NCPI-NAD-TIP
Cc : 'Christian Huitema'; teemu.savolainen at nokia.com; ajs at shinkuro.com; behave at ietf.org; draft-boucadair-behave-dns-a64 at tools.ietf.org
Objet : draft-boucadair-behave-dns-a64-00.txt [was RE: [BEHAVE] I-D Action:draft-ietf-behave-dns64-01.txt]

> FYI, we have submitted a draft to describe the A64 record for 
> IPv4-mapped IPv6 addresses. An updated version of the draft 
> will be submitted soon

draft-boucadair-behave-dns-a64-00 requires the DNS64 and the host to implement
a new DNS resource record, A64, in order to learn if the DNS64 synthesized a
response.

Instead, have you considered just having the host query an
existing DNS64 with the CD and DO bits set (which disables the
DNS64's AAAA synthesis) and have the host do its own DNS64 
processing?  See item #3 in
http://tools.ietf.org/html/draft-ietf-behave-dns64-01#section-5.5

If you have considered that technique, I expect you found some sort
of disadvantage to that technique.  Please share.

-d