{multiple quotes}
On Wed, Sep 13, 2006 at 09:23:11AM +1000, Mark Andrews wrote:
> > was more to say "." != "no address" (waiting for someone to point me to the
> > existing (bad) precedent).
>
> RP.
Bingo. RFC 1183 says:
The root domain name (just ".") may be specified for <mbox-dname> to
indicate that no mailbox is available.
[...]
RP records cause no additional section processing. (TXT additional section
processing for <txt-dname> is allowed as an option, but only if it is
disabled for the root, i.e., ".").
The special meaning is part of the initial spec, precautions to protect "."
are in there -- and this predates RFC 2606.
Tony Finch:
> The "no service here" meaning of this kind of "." is explicitly specified
> for SRV records.
Yes, RFC 2782 says
Target
The domain name of the target host. There MUST be one or more
address records for this name, the name MUST NOT be an alias (in
the sense of RFC 1034 or RFC 2181). Implementors are urged, but
not required, to return the address record(s) in the Additional
Data section. Unless and until permitted by future standards
action, name compression is not to be used for this field.
A Target of "." means that the service is decidedly not
available at this domain.
Again, it's in the original spec (here and RFC 2052), "." additional
processing is to be avoided (although these paragraphs have to be polished
for 2782bis) and SRV predates RFC 2606.
Joe Abley:
> I've seen many people use "." as part of MX RDATA to indicate that a
> host should not receive mail (e.g. "PRINTER.EXAMPLE.COM. 3600 IN MX
> 0 ."). I seem to remember that meaning is documented informally in
> Cricket Liu's book, but I could be wrong about that (I don't have a
There was an I-D promoting this, as well. The problem here, as with RNAME,
is that it retroactively applies a special meaning to the "." domain.
For MX RRs thats bad due to the additional section processing, which
should not occur for the SOA RR as per RFC 1035 (although it is done
for MNAMEs)
-Peter
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