[idn] IDN biting off more than it can chew

["D. J. Bernstein" <djb@cr.yp.to>]

John C Klensin writes:
> Absolutely.  And, if we get it seriously wrong, the DNS becomes
> ambiguous and unmanageable, and we have no way back.  Hence,
> conservatism is in order, IMO.

This is one of the reasons that programs shouldn't do nameprep.

Suppose we teach applications these horribly complicated rules---rules
in which we're still finding major errors---for converting bad strings
to good strings. Suppose it turns out that this was a huge mistake: for
example, users are constantly confusing uppercase Beta with uppercase B.

We'll never be able to get rid of the conversion. We'll be stuck with it
for compatibility, just as we're stuck with treating uppercase ASCII as
equivalent to lowercase ASCII today.

If, on the other hand, applications don't do any conversion, and
registrars prohibit the bad characters, then the bad characters simply
won't work. There will be only one way to type a domain name. If this
turns out to be a mistake, we can change it later, without breaking
anything. This is the simple, clean, conservative approach.

---Dan