Subject: Re: [apps-discuss] I-D Action: draft-ietf-appsawg-nullmx-05.txt

From: Douglas Otis <[email-masked]>
Date: Thu, 10 Jul 2014 17:00:51 -0700

On Jun 27, 2014, at 11:00 AM, John Levine <[email-masked]> wrote:

> This version fixes ID nits and has a little more minor editorial cleanup.
> 
> For the record, I confirm that to my direct, personal knowledge there
> is no IPR related to this document.

Dear John,

When this idea first emerged, the seemingly simple concept was discussed with those managing DNS root servers.  What they mentioned was use of "." as a host-name flag returns no address answer which then means DNS depends on RFC2308 from 1998 to suppress what might be significant levels of inadvertent queries.  This was one of the discoveries following its use when defining SRV records.  This problem happened even though the SRV definition from 2000 warns against actually making queries against this specific host name.

RFC2782
,--
Usage rules

   A SRV-cognizant client SHOULD use this procedure to locate a list of
   servers and connect to the preferred one:

        Do a lookup for QNAME=_service._protocol.target, QCLASS=IN,
        QTYPE=SRV.

        If the reply is NOERROR, ANCOUNT>0 and there is at least one
        SRV RR which specifies the requested Service and Protocol in
        the reply:

            If there is precisely one SRV RR, and its Target is "."
            (the root domain), abort.
'--

MX records offer no such warning and also tend to experience excessive amounts of nuisance traffic.   The null mx record concept focuses this nuisance traffic at the roots rather than allowing it to be distributed.   What is the status on support for RFC2308 and how well is "." (root domain) handled by DNS clients to estimate the possible effects on roots by a null mx scheme?  Perhaps review of SRV records might offer a means to make estimates.

Regards,
Douglas Otis

>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the Applications Area Working Group Working Group of the IETF.
>> 
>>       Title           : A NULL MX Resource Record for Domains that Accept No Mail
>>       Authors         : John Levine
>>                         Mark Delany
>> 	Filename        : draft-ietf-appsawg-nullmx-05.txt
>> 	Pages           : 6
>> 	Date            : 2014-06-27
>> 
>> Abstract:
>>  Internet mail determines the address of a receiving server through
>>  the DNS, first by looking for an MX record and then by looking for an
>>  A/AAAA record as a fallback.  Unfortunately this means that the A/
>>  AAAA record is taken to be mail server address even when that address
>>  does not accept mail.  The NULL MX RR formalizes the existing
>>  mechanism by which a domain announces that it accepts no mail, which
>>  permits significant operational efficiencies.
>> 
>> 
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-appsawg-nullmx/
>> 
>> There's also a htmlized version available at:
>> http://tools.ietf.org/html/draft-ietf-appsawg-nullmx-05
>> 
>> A diff from the previous version is available at:
>> http://www.ietf.org/rfcdiff?url2=draft-ietf-appsawg-nullmx-05
> 
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