Comments on draft-ietf-idnabis-defs-10

[Patrik Fältström]

On 30 aug 2009, at 21.54, Patrik Fältström wrote:

> On 30 aug 2009, at 20.22, Wil Tan wrote:
>
>> However, if certain characters in an A-label have
>> been uppercased, the Punycode decoding algorithm (due to its mixed- 
>> case
>> annotation feature) may produce invalid U-label because the ASCII  
>> characters
>> will be in capital letter form.
>
> Can you give examples of when this happens? I can not see this  
> result in the punycode algorithm. I also just did some tests with  
> mixed ascii, latin and chinese characters, and can not reproduce.

I still do not understand what the problem is, and I am waiting for  
someone to give examples of the above scenario.

I.e. if you have U-label 1:

- fältström

turn it into an A-label:

- xn--fltstrm-5wa1o

randomly casefold the characters:

- xN--fLtStRm-5Wa1O

turn into U-label:

- fäLtStRöm

This only differs in the casing of the ascii characters, i.e. still  
follows the matching rules for DNS for ascii, and have exact matches  
for the rest.

So, casefold of the ascii in the A-label only result in casefold of  
the ascii in the U-label.

     Patrik