Re: Problems with spf testsuite and dns specification

Julian Mehnle <[email protected]>
Newsgroups gmane.mail.spam.spf.devel
Message-ID <[email protected]>
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Stefano Bagnara wrote:
> Julian Mehnle ha scritto:
> > Stefano Bagnara wrote:
> > > IMHO the problem is not "to compact or not to compact". The problem
> > > is requiring a PermError (a specific different action) on something
> > > that the DNS spec tell us is not different from a single record.
> > > To use your "question": show me any other DNS application that
> > > specifies a different behaviour on multiple identical RRs ;-)
> >
> > SMTP, MX records.  Multiple identical RRs make a typical SMTP client
> > perform multiple lookups, not one.  At least, RFC 2821 section 5
> > doesn't specify any MX RR compaction.
>
> Well, on SMTP you will find me prepared as I'm a developer of Apache
> JAMES SMTP server :-)
>
> rfc2821 DOES NOT add any specification related to multiple identical MX
> RRs: it simply rely on what the underlying DNS implementation do, as it
> is supposed to.

Exactly.  And if an SMTP client receives...

  example.com.  MX  10 mta.example.com.
  example.com.  MX  10 mta.example.com.

... then it will likely behave differently than if it had received just 
_one_ of those records (i.e. it will try to connect to mta.example.com two 
times if that host isn't reachable).  RFC 2821 does NOT specify that such 
identical records must be treated as a single one.  So why should RFC 
4408?

> The important thing to be noticed is that SMTP does not add any
> specification that will alter the final behavior in a critical way
> depending on the underlying dns chain "compression" policy.

That's true.

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