Re: [idn] Forbidden characters

[David Hopwood <david.hopwood@zetnet.co.uk>]

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Dan Oscarsson wrote:
> Yves Arrouye <yves@realnames.com> wrote:
> >Dan Oscarsson wrote:
> >> If we define that nameprep must be done before names are sent
> >> over the DNS protocol we get a lot of characters that are
> >> forbidden in host names.
> >>
> >> For example: all upper case letters, double width and circled letters.
> >>
> >> This is quite a change from current usage where both upper
> >> and lower case is allowed in host names.
> >
> >They are not forbidden: they will get folded to something else. So you can
> >still write and register your names with, say, U+00DC LATIN CAPITAL LETTER U
> >WITH DIAERESIS and U+2462 CIRCLED DIGIT THREE. They can be used in your
> >applications and by your users. They are just strictly euqivalent to U+00FC
> >LATIN SAMLL LETTER U WITH DIAERESIS and [U+0033 DIGIT THREE]. Just like 'A'
> >and 'a' are strictly equivalent today in DNS.
> 
> But today the name service itself can handle both 'A' and 'a', and you
> can register a name with 'A' in it. When nameprep is required to be
> done before a name enters the name service, the name service cannot
> itself handle the above characters. So in the name service they are
> forbidden and cannot be returned from it.

So what? Why is it a problem if uppercase non-ASCII characters (and various
other non-NFKC-normalised characters) are not returned in reverse lookups?
End-users see the results of a reverse lookup quite infrequently, and when
they do, I doubt that they care whether it has uppercase characters or not.

- -- 
David Hopwood <david.hopwood@zetnet.co.uk>

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