[dns-operations] xn--

[jeffb]

I also had trouble finding much discussion on it, but here's a draft
standard (from 2001) that seems to cover some of the basis of selecting
one: https://www.ietf.org/proceedings/50/I-D/idn-aceid-01.txt

More or less, it seems they were chosen arbitrarily, at least at that
time..:

Therefore, the current situation letting independent ACE proposal
> authors arbitrarily select an ACE identifier, hence permitting domain
> name registrants registrer such names, may hinder deployment of MDN
> technology.


Not seeing any further follow-up on the draft.

Jeff

On Wed, Jun 25, 2025 at 11:38 PM Gihan Dias <gihan at domains.lk> wrote:

> On 26/06/2025 09:02, jeffb wrote:
>
> Possibly a good place to start:
> https://datatracker.ietf.org/doc/html/rfc3490
>
> Specifically Section 5.. though I have no idea how to register/who
> controls ACE prefixes:
> https://datatracker.ietf.org/doc/html/rfc3490#section-5
>
> Jeff,
>
> Thanks.
>
> It doesn't discuss *why* xn-- was chosen, though it does say:
>
> The ACE prefix, used in the conversion operations (section 4 <https://datatracker.ietf.org/doc/html/rfc3490#section-4>), is two
>    alphanumeric ASCII characters followed by two hyphen-minuses.  It
>    cannot be any of the prefixes already used in earlier documents,
>    which includes the following: "bl--", "bq--", "dq--", "lq--", "mq--",
>    "ra--", "wq--" and "zq--".
>
> However, I couldn’t find a discussion of ACE prefixes, or how any of the
> above were selected.
>
> Gihan
>


-- 
jeffb | jeffb at jeffb.net
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