Re: [xmpp] [Technical Errata Reported] RFC7622 (5769)

[Florian Zeitz <[e-mail]>]

>> The intend of 7622 (in particular Section 3.2.1) as I recall it was that
>> A-labels would generally be valid in JIDs.
> 
> The question here is: Do you mean A-label or "a string which is (also) a
> valid A-label"?
> 
Maybe you want to enlighten me what the distinction is you make here,
and how it is useful?
I can only imagine that it is one of intent. Yet, I'm having a hard time
imagining people creating labels that consist of 'xn--' followed by a
valid punycode encoding of IDNA-valid codepoints, but insisting these
are not an A-label.

>> However, software would be
>> required to process (user) input containing A-labels so that any
>> JID-slots would only contain U-labels on the wire.
> 
> Exactly. This is an important insight: Any string which is a valid
> A-label may be valid in the domainpart of a Jid. However, if this string
> got derived from an U-label, then you did something wrong. As JID
> domainparts constructed from DNS names which contain U-label(s) should
> conserve the U-label presentation (and not use the ACE/A-label form).
> 
It seems to me that you are implying that software should not convert
something that looks like an A-label to a U-label either?
I.e. each label of a domainpart always has to remain in the
representation provided by the user?

Regards,
Florian