houston.rr.com MX fubar?

Mark Andrews Mark_Andrews at isc.org
Tue Jan 15 03:23:25 UTC 2008


In article <bb0e440a0801141838r736462dey64094e555cd6d0a6 at mail.gmail.com> you write:
>
>On Jan 14, 2008 5:08 PM, Tony Finch <dot at dotat.at> wrote:
>
>> the "." convention then it will look up the root's AAAA and A records,
>> which is stupid but should cause the message to bounce as desired. However
>> if it does implement the convention (just like the "usage rules" for a SRV
>> record target of "." in RFC 2782) then it can skip the address lookups and
>> save the root some work. (It can also produce a better error message.)
>> This really ought to be explained in draft-delany-nullmx.
>
>The draft died.  And I think this stuff about looking up A / AAAA for
>the root was certainly raised in the IETF sometime back.  Not that
>there isnt enough junk traffic (and DDoS etc) coming the roots' way
>that this kind of single lookup would get lost in the general noise ..
>
>Might want to revive it and take it forward?  I rather liked that
>draft (and Mark Delany cites me in the acknowledgements as I suggested
>a few wording changes for the definition of a null MX - dot terminated
>null string, STD13 etc, during his drafting of the document)
>
>--srs
>
>-- 
>Suresh Ramasubramanian (ops.lists at gmail.com)

        There are lots of places in the DNS where "." makes sense
        as a null indicator.  RP uses it today, as does SRV.  MX
        should use it and fallback to A should be removed.  It
        actually takes more cache space to record that a MX record
        does not exist than it takes to record that a A or AAAA
        record exists (SOA rdata is atleast 22 octets).

        draft-ietf-dnsop-default-local-zones used it for SOA RNAME
        but was changed under WG pressure.

        A and AAAA should use 0.0.0.0 and :: to indicate that a host
        exists but is not currently connected.

        Mark



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