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Re: Last Call: draft-jabley-sink-arpa (The Eternal Non-Existence of SINK.ARPA (and other stories)) to BCP

2009-12-22 08:50:54
On Mon, 21 Dec 2009, SM wrote:

If I understood the story, it is to get compliant MTAs not to attempt mail
delivery to domains which do not wish to accept mail.  This does not really
solve the implicit MX question but that's another story.

The idea of using sink.arpa as an MX target (like the null MX proposal) is
to define a conventional form of MX record that indicates a domain is not
a valid mail domain. It solves the implicit MX problem for sites that use
it, but obviously not for sites that don't. It's much cheaper to deploy
than RFC 1864 (which specifies the SMTP 521 initial greeting).

Here's some text from Section 5.1 of RFC 5321: [snip]

As the intended status of this draft is BCP, it may have to take into
consideration the above text from RFC 5321 and see how to resolve the issue.

What issue? As far as I can tell there's no conflict between Joe's draft
and RFC 5321, except that the choice of words in the example needs
improvement.

In particular, this sentence:
                                                  Installing an MX
       record whose RDATA includes SINK.ARPA in the EXCHANGE field
       ([RFC1034]) should cause compliant MTAs to make no connection:
       SINK.ARPA does not exist, and A and AAAA records should not be
       used when an MX record is present.

ought to be written:
                                                  Installing an MX
       record whose RDATA includes SINK.ARPA in the EXCHANGE field
       ([RFC1035]) shall cause compliant MTAs to make no connection:
       SINK.ARPA does not exist, and A and AAAA records shall not be
       used when an MX record is present.

so that it agrees with the strength of the RFC 2119 mustard in RFC 5321.
Also the reference to RFC 1034 should be a reference to RFC 1035 since
that is where the EXCHANGE field is specified.

Note that any MX target domain name with no A or AAAA RRs will do the same
job as sink.arpa or . (the dns root as proposed in the null MX draft); the
advantage of a conventional name is that MTAs can skip the target address
lookups since they already know the MX is unusable..

Tony.
-- 
f.anthony.n.finch  <dot(_at_)dotat(_dot_)at>  http://dotat.at/
GERMAN BIGHT HUMBER: SOUTHWEST 5 TO 7. MODERATE OR ROUGH. SQUALLY SHOWERS.
MODERATE OR GOOD.
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