referencing IDNA2008 (and IDNA2003?)

Alireza Saleh saleh at
Fri Oct 22 21:29:03 CEST 2010

Thanks John for the answer. By valid i meant a label that corresponds to 
a valid U-label. However it maybe valid under IDNA2003 or 2008


On 10-10-22 10:53 PM, John C Klensin wrote:
> --On Friday, October 22, 2010 22:03 +0330 Alireza Saleh
> <saleh at>  wrote:
>> So what happened if someone types a vali PunyCode but with
>> capital letters as an address.
> Do you mean "Something that looks like an A-label with one or
> all letters in capitals"?  If so, it isn't a valid IDNA2008
> A-label. However, for IDNA2003 compatibility, I would strongly
> recommend lower-casing ASCII strings that appear to be A-labels
> before processing them) -- fortunately, one of the few things in
> this space we are pretty sure we know how to do is to convert
> all-ASCII strings to lower case.  :-)
> If you mean "something that looks like a U-label but that
> contains letters in capitals", it is invalid under IDNA2008 (See
> Rule B, Section 2.2 of RFC 5892).  It would be valid under
> IDNA2003 (because case folding is built into Nameprep), but
> cannot be derived by applying ToUnicode to a valid string
> produced by ToASCII (more or less an A-label).
> So I'm not quite sure what you mean by "valid PunyCode".
>      john
> _______________________________________________
> Idna-update mailing list
> Idna-update at

More information about the Idna-update mailing list