[cabfpub] Ballot 202 - Underscore and Wildcard Characters

Jacob Hoffman-Andrews jsha at letsencrypt.org
Thu Jul 20 16:16:08 MST 2017

If people are curious, as I was, about why RFC 5890 restricts use of
Reserved LDH Labels, here is what I believe to be the relevant paragraph:


> Labels within the class of R-LDH labels that are not prefixed with
> "xn--" are also not valid IDNA labels.  To allow for future use of
> mechanisms similar to IDNA, *those labels MUST NOT be processed as*

*> ordinary LDH labels by IDNA-conforming programs* and SHOULD NOT be
> mixed with IDNA labels in the same zone.

(emphasis mine)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://cabforum.org/pipermail/public/attachments/20170720/e677d063/attachment.html>

More information about the Public mailing list