Re: [DNSOP] Further ANAME minimization /\ Ray convergence

Kevin Darcy <kevin.darcy@fcagroup.com> Thu, 08 November 2018 21:05 UTC

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From: Kevin Darcy <kevin.darcy@fcagroup.com>
Date: Thu, 8 Nov 2018 16:05:28 -0500
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Subject: Re: [DNSOP] Further ANAME minimization /\ Ray convergence
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It should be pointed out that the Autodiscover subsystem of Microsoft
Office uses SRV in a very *degenerate* way. It ignores all fields other
than target. In my testing, I believe I also proved that it doesn't fail
over if presented multiple SRV RRs in a response. So, basically it's a
one-to-one mapping between a (fixed-prefix + domain-specific-suffix) name
and a hostname, something that syntactically could have been accomplished
more simply using, say, PTR (which, contrary to common misconception, is
*not* limited to reverse lookups).

Personally, I would exclude Autodiscover from any list of "things which use
SRV", since its use is not consistent with the spirit or the letter of the
SRV RFCs.


                         - Kevin


On Wed, Nov 7, 2018 at 4:46 PM Michael J. Sheldon <msheldon@godaddy.com>;
wrote:

>
>
> On 11/07/2018 02:13 PM, Tim Wicinski wrote:
> > Tony says this:
> >
> > " It isn't a judgment about what's good, but an observation about what
> > is done."
> >
> > I can't stress this enough - when you see ALIAS records at zone cuts
> > that point to a database server,
> > already, then we've missed the "server specific" ball.
> >
> > And can someone show a significant number of SRV examples outside of SIP
> > and some gaming
> > servers?
>
> From data in our systems, most common in order is _autodiscover and
> other email/calendar related, then sip, then jabber/xmpp. After that,
> the numbers are far less significant.
>
>
>
> --
> Michael Sheldon
> Dev-DNS Services
> GoDaddy.com
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