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Re: IPV6: Where are we? (SMTP)

2008-04-07 13:47:28

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 records.

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 precludes A-Fallback]).

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.

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