Re: IPV6: Where are we? (SMTP)
At 22:17 -0400 on 04/06/2008, Hector Santos wrote about IPV6: Where
are we? (SMTP):
Why has this not been discussed as an alternative to AAAA? It would
seem to me that A6 which has type value of 38 is a reasonable item
to be discussed if we also going to discussed lookups for AAAA
I seem to have the impression that the A6 version was depreciated in
favor of the AAAA method due to AAAA being straight forward (it is
just the IPv6 version of the A) while A6 was VERY complex to define
(as DNS records) and implement (in code and resolvers). They were two
different ways of defining IPv6 addresses and in the head-to-head
competition AAAA won.
As to the Implicate MX question, I think we should take the
conservative stance that direct AAAA references should be banned
RIGHT NOW with this a possible relaxation of this restriction to be
addressed at a later date via an RFC on this issue.
IPv4-Only MTA FQDNs as at present - Optional (but suggested) MX with
A-Fallback in the absence of the MX.
IPv6 MTA FQDNs ONLY via MX (with a recommendation that there be IPv4
MTAs which MUST be listed in the MX [since the existence of the MX
By INITIALLY saying "No AAAA-Fallback" we can address the issue later
while allowing it NOW will prevent us from banning/depreciating it in
the future (as we can see with trying to depreciate A-Fallback). IMO
there is no VALID excuse for allowing AAAA-Fallback except for the
"We Allow A-Fallback so we should allow AAAA-Fallback" claim. I see
the existence of A-Fallback support as an invalid issue to avoid
justifying the need to not require the use of MX.