Re: [DNSOP] ANAME loop detection

[Matthew Pounsett <[e-mail]>]

On Thu, 4 Jul 2019 at 10:54, Matthijs Mekking <[e-mail]>
wrote:

> Matthew,
>
> > I would say they should rely on that.  Why shouldn't they?  Isn't our
> > goal to get downstream servers to adopt the extension and do their own
> > lookup?  The server-side lookups and sibling records are bolt-ons to
> > handle the adoption period.  Remember, this record is geared toward
> > customers of CDNs being able to do get similar behaviour to:
> > www.example.com <http://www.example.com>. IN CNAME webfarm.cdn.net
> > <http://webfarm.cdn.net>.
> > at the apex of example.com <http://example.com>.  That was the original
> > problem we're trying to solve.  I read your statement above about "the
> > service they provide their customers" being about the CDN resolving
> > webfarm.cdn.net <http://webfarm.cdn.net>, which most CDNs can already do
> > within their own infrastructure.
>
> I am talking about DNS providers that perform CNAME at the Apex like
> features: a customer goes to them and opts in to this feature. Such a
> provider wants to make sure that it is providing the behavior the
> customer expects and thus wants to make sure it hands out appropriate
> addresses.
>

And "CNAME at the Apex like feeatures" is to hand out a CNAME and let the
downstream server process that.  It may include additional information from
other zones it is authoritative for, but it doesn't do side-lookups.  I
think that's the behaviour we should be aiming for, and to do that some
sort of "I understand ANAME" signal would allow the authoritative server to
behave more like CNAME.


>
> Also what is wrong with an authoritative server already giving out more
> optimal answers than just the ANAME and sibling address records?
>

Nothing, as long as it's not going to increase the time it takes to respond
to the query.

But, you didn't respond to my question.  Let me rephrase it a bit:  If the
authoritative server knows the client understands ANAME, why would the
authoritative server not assume that any additional data it supplies will
be thrown away?    I suggest that it would be wise for an authoritative
server to assume that a client that understands ANAME will resolve its own
ANAME and ignore any other data it gets.


>
> > Option #2 gets similar behaviour but at the cost of additional lookups.
> > #3 and #4 don't work well in the presence of server farms.
>
> If addresses are in the response to the ANAME request there is no
> difference in number of lookups between 2 and 3 I think.
>

Did you mean "lookups between 1 and 2"?    I didn't say anything about the
number of lookups required for 3.  I think 3 and 4 are poor choices because
they won't behave well with most server farms.