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Re: current usage of AAAA implicit MX?

2008-04-06 00:40:11

Russ Allbery wrote:
"Robert A. Rosenberg" <hal9001(_at_)panix(_dot_)com> writes:

It's not that it's technically difficult so much as that it's dubious from
a layering perspective, at least from where I sit.  It requires I
introduce IPv6-specific code (and hence ifdefs for systems without IPv6
constants and so forth) into an application that otherwise would not need
any and would be entirely stack-agnostic.

I guess I'm questioning the cost/benefit analysis being applied here.  Are
we really fixing a significant enough problem by not having implicit MX
fallback for IPv6-only nodes to warrant introducing IPv6-specific logic
into mail routing applications that otherwise could use stack-agnostic
logic, and warrant the corresponding increase in complexity of
specification and reasoning about mail systems?  It's setting off
aesthetic red flags.  This is the sort of design decision whose
consequences are fuzzy, and hence tend to have an underestimated impact.

+1 Well stated.

This is my main concern with this last minute change request which sounds to me is making to attempt to give IPv4 systems "a little" knowledge about IPv6 if only at the query level possibly only for some spam detection purpose. There is no other benefit short of making the IPv4 system IPv6 aware at the SMTP TCP transport level and 2821bis is clearly not ready for full blown IPv6 support.


Hector Santos, CTO