Re: [idn] length restrictions on IDN label

["Adam M. Costello" <idn.amc+0@nicemice.net.RemoveThisWord>]

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

> If UTF8-encoded, that valid 8bit label will exceed 63 octets limits
> (up to 168 octets or more)

True.

> which is imposed by RFC1035 even upon non-ASCII 8bit labels .

Yes, but labels in DNS containing octets >= 128 are not
internationalized labels, because internationalized labels use only
octets <= 127 in DNS.  Labels in DNS containing octets >= 128 are
mysterious creatures that have no standard interpretation as text
(because ASCII is the only text encoding used by the DNS standard).

> IDNA section 6.3 does not rule out that utf8 encoded labels may be
> used in DNS wire protocols in the future.

In which case the specification of those future wire protocols will need
to deal with the fact that UTF-8 forms of internationalized labels can
have more than 63 octets.  (255 is an upper bound, though not the least
upper bound.)

AMC