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Re: [idn] length restrictions on IDN label

Adam M. Costello wrote:
Soobok Lee <lsb@postel.co.kr> wrote:


Yes, but labels in DNS containing octets >= 128 are not
internationalized labels, because internationalized labels use only
octets <= 127 in DNS.

Really ?

Really.


"UTF-8 forms of internationalized labels" are not "internationalized
labels" ?

The UTF-8 form of an internationalized label is an internationalized
label. But that's irrelevant, because labels in DNS containing octets

= 128 are not UTF-8. The only text encoding used by DNS is ASCII

(according to the current DNS standard).  The octets >= 128 in DNS are
non-ASCII, but that doesn't mean they are UTF-8.  We don't know what
they are, except octets.
But, UTF-8 forms make subset of the entire set of non-ASCII forms. Thus,
the utf8-compliant subset has been under the oversall length restriction imposed
by RFC1035 on the entire set.

The UTF-8 form of an internationalized label is an internationalized
label, but a sequence of octets with no charset tag is not an
internationalized label (it's not even text).
UTF8-form of labels carry no language/encoding tag in them (unlike MIME does.)
They can be only assumed or negotiated through other channel in protocols.

Soobok Lee


So I stand by my position quoted at the top of this message.

AMC