"SRV-Style" labels and "IDN"

[Alexander Mayrhofer]

Hi,

I'm currently reading through the idnabis-Documents, and didn't find a
clear answer to the following issue:

2.3.2.3 of draft-ietf-idnabis-defs-08 defines an IDN as "name that may
contain any mixture of NR-LDH-labels, A-labels, or U-labels".  From what
i read, that means that an IDN may not contain a "SRV-style" label,
starting with an underscore. A few lines later, it is clarified that
such a label is not an "Internationalized Label". There's no text about
those labels in the definition of "IDN". Therefore, from the definition,
the following example:

   _sip._tcp.<A-Label>.<tld>

Would not be an IDN. My questions now, unless i have missed something:

- Is my assumption correct that the example is not an IDN?
- If it is not an IDN, what is it? 

Thanks,

Alex Mayrhofer
nic.at