<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif">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: <a href="https://www.ietf.org/proceedings/50/I-D/idn-aceid-01.txt">https://www.ietf.org/proceedings/50/I-D/idn-aceid-01.txt</a></div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">More or less, it seems they were chosen arbitrarily, at least at that time..:</div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><span style="font-family:Arial,Helvetica,sans-serif">Therefore, the current situation letting independent ACE proposal<br></span>authors arbitrarily select an ACE identifier, hence permitting domain<br>name registrants registrer such names, may hinder deployment of MDN<br>technology.</blockquote><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">Not seeing any further follow-up on the draft.</div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">Jeff</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Wed, Jun 25, 2025 at 11:38 PM Gihan Dias <<a href="mailto:gihan@domains.lk">gihan@domains.lk</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<div>On 26/06/2025 09:02, jeffb wrote:<br>
</div>
<blockquote type="cite">
<div class="gmail_default" style="font-family:tahoma,sans-serif">Possibly
a good place to start: <a href="https://datatracker.ietf.org/doc/html/rfc3490" target="_blank">https://datatracker.ietf.org/doc/html/rfc3490</a></div>
<div class="gmail_default" style="font-family:tahoma,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:tahoma,sans-serif">Specifically
Section 5.. though I have no idea how to register/who controls
ACE prefixes: <a href="https://datatracker.ietf.org/doc/html/rfc3490#section-5" target="_blank">https://datatracker.ietf.org/doc/html/rfc3490#section-5</a></div>
</blockquote>
<p>Jeff,</p>
<p>Thanks.</p>
<p>It doesn't discuss <i>why</i> xn-- was chosen, though it does
say:</p>
<blockquote>
<pre style="box-sizing:border-box;font-family:"Noto Sans Mono",SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;font-size:16px;display:block;overflow:visible;padding:0px;width:80ch;white-space:pre-wrap;color:rgb(33,37,41);font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">The ACE prefix, used in the conversion operations (<a href="https://datatracker.ietf.org/doc/html/rfc3490#section-4" style="box-sizing:border-box;color:rgb(13,110,253);text-decoration:underline" target="_blank">section 4</a>), 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--".</pre>
<p></p>
</blockquote>
<p>However, I couldn’t find a discussion of ACE prefixes, or how any
of the above were selected.</p>
<p>Gihan<br>
</p>
</div>
</blockquote></div><div><br clear="all"></div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature">jeffb | <a href="mailto:jeffb@jeffb.net" target="_blank">jeffb@jeffb.net</a></div>