[dns-operations] TLD(s) for private use

[Stephane Bortzmeyer]

Funny, we just had a long discussion in an IETF working group about
that :-)

On Wed, Sep 06, 2017 at 10:28:23AM +0100,
 James Stevens <James.Stevens at jrcs.co.uk> wrote 
 a message of 26 lines which said:

> Apart from those in RFC-6761, is there any TLD, or format of TLD,
> that can be used for private use that is guaranteed never to be
> allocated?

No. (Or, to be careful, "not yet".)

> I'm guessing dot-ZZ might fit that criterion, on the basis no country will
> ever get it,

I wouldn't be so sure, ISO 3166 does not reserve that code in any way.

> Or is the correct procedure to be using something like
> "data.invalid."?

No, the "correct" (or at least recommended) procedure is to use a
subdomain of one of your domains. (If you are example.com, use
priv.example.com.) One of the reasons for this recommendation is the
need for uniqueness (think merging and acquisition, and the problems
of people who had to merge RFC-1918 networks.)