Subject: (ngtrans) DNS text in draft-ietf-ngtrans-mech-v2-00.txt

From: Erik Nordmark <[email-masked]>
Date: Wed, 31 Jul 2002 19:41:00 +0200 (CEST)

The only remaining issue I have for the document (and thanks for the careful
reviews so far!) is:
   -    Should all of section 2.2 (DNS stuff) be removed?  It duplicates
        [19].

 [19]   R. Draves, "Default Address Selection for IPv6", Work in
        progress, draft-ietf-ipv6-default-addr-select-08.txt, June
        2002.

Let's try to resolve this on the mailing list.

Section 2.2 says in its entirety:

2.2.  DNS

   The Domain Naming System (DNS) is used in both IPv4 and IPv6 to map
   between hostnames and IP addresses.  A new resource record type named
   "AAAA" has been defined for IPv6 addresses [6].  Since IPv6/IPv4
   nodes must be able to interoperate directly with both IPv4 and IPv6
   nodes, they must provide resolver libraries capable of dealing with
   IPv4 "A" records as well as IPv6 "AAAA" records.

   DNS resolver libraries on IPv6/IPv4 nodes MUST be capable of handling
   both AAAA and A records.  However, when a query locates an AAAA
   record holding an IPv6 address, and an A record holding an IPv4
   address, the resolver library MAY filter or order the results
   returned to the application in order to influence the version of IP
   packets used to communicate with that node.  In terms of filtering,
   the resolver library has three alternatives:

   -    Return only the IPv6 address(es) to the application.

   -    Return only the IPv4 address(es) to the application.

   -    Return both types of addresses to the application.

   If it returns only the IPv6 address(es), the application will
   communicate with the node using IPv6.  If it returns only the IPv4
   address(es), the application will communicate with the node using
   IPv4.  If it returns both types of addresses, the application will
   have the choice which address to use, and thus which IP protocol to
   employ.

   If it returns both, the resolver MAY elect to order the addresses --
   IPv6 first, or IPv4 first.  Since most applications try the addresses
   in the order they are returned by the resolver, this can affect the
   IP version "preference" of applications.

   The decision to filter or order DNS results is implementation
   specific.  IPv6/IPv4 nodes MAY provide policy configuration to
   control filtering or ordering of addresses returned by the resolver,
   or leave the decision entirely up to the application.

   An implementation MUST allow the application to control whether or
   not such filtering takes place.

   More details on this subject are specified in [19].

---

Is the above information still useful? In conflict with the address selection
dociment? Should the document just refer
to the address-select document for all of this?

   Erik

---

From: Keith Moore <[email-masked]>
Date: Wed, 31 Jul 2002 15:03:35 -0400

this section needs changes.

it is fundamentally unacceptable for resolver libraries to interfere
with the results of a DNS query.    the resolver is NOT smarter than
the applications.

Keith

---

From: Erik Nordmark <[email-masked]>
Date: Thu, 1 Aug 2002 01:47:20 +0200 (CEST)

> with the results of a DNS query.    the resolver is NOT smarter than

Send suggested text.

Thanks,
   Erik