[dns-operations] AXFR support for custom DNS features (Was: Recommended zone serial number format for over 100 changes / day)

[Robert]

On 1 April 2016 at 10:26, Andrew Sullivan <ajs at anvilwalrusden.com> wrote:
> On Fri, Apr 01, 2016 at 10:13:08AM -0700, Robert wrote:
>> So then the preference would be dropped?
>
> Anything that _isn't_ an RR would be dropped, yes.  So, …

That's the crux of my confusion.  I've read numerous posts on this
mailing list and others where people want AXFR support from commercial
DNS providers that support features which aren't supported by AXR -
with the consensus being those unsupported records must be dropped.
It doesn't sound like a usable feature if only parts of a zone are
transferred.

I mostly get the AXFR into a commercial DNS provider because you you
can set the constraints on your DNS system to only support those
supported by AXFR, though not all commercial DNS providers even
support all of the RRTypes supported by AXFR so you'd still have to be
careful there.

For those who want AXFR out from a commercial DNS provider, why do you
want it if it isn't expected to work?  Would you want the commercial
DNS provider to restrict the use of those unsupported by AXFR
pseudo-RRTypes within a zone you've enabled AXFR for or would you
trust yourself to not use them?