Comments on draft-ietf-idnabis-defs-10

James Mitchell james.mitchell at
Tue Sep 1 06:14:37 CEST 2009

> > XN--KGBECHTV is a valid A-label;
> No.  Because it cannot be produced by the defined transformation
> from a U-label, it is not.  The difference between it an a valid
> A-label is harmless, and both translate back to exactly the same
> U-label, but that doesn't make it a valid A-label.

Punycode does not require output to be in any particular case.  I have copied from RFC3492 Page 8 below for convenience

'An encoder SHOULD output only uppercase forms or only lowercase forms, unless it uses mixed-case annotation'

Therefore KGBECHTV and kgbechtv are both valid outputs of the punycode algorithm.


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