Subject: Re: [idn] length restrictions on IDN label

From: Erik Nordmark <[email-masked]>
Date: Tue, 15 Oct 2002 14:28:23 +0200 (CEST)

> If this limit is a new and independent from the underlying "native" DNS,
> what is the reason for it?  If it is not independent, why duplicate it?

It isn't independent since the limit derives from the label length limit
in the DNS protocol, but the limit is also a function of the amount
of compression that punycode performs.

The fact that punycode will never generate a string with less
number of code points than the number of code points in the input
is far from obvious, hence it makes sense in my mind to state this limit.

  Erik

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From: Dave Crocker <[email-masked]>
Date: Tue, 15 Oct 2002 07:16:50 -0700

Erik,

Tuesday, October 15, 2002, 5:28:23 AM, you wrote:
EN> It isn't independent since the limit derives from the label length limit
...
EN> The fact that punycode will never generate a string with less number of
EN> code points than the number of code points in the input is far from
EN> obvious, hence it makes sense in my mind to state this limit.

makes sense.  thanks.

/d
-----
Dave <mailto:[email-masked]>

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From: Dave Crocker <[email-masked]>
Date: Tue, 15 Oct 2002 00:59:33 -0700

Erik,

Monday, October 14, 2002, 7:29:11 AM, you wrote:

EN> It might also be useful to make the IDNA specification more clear about
EN> the length limit and its implications somewhere in the document.
EN> Strawman:         The length limit for internationalized labels is the
EN> limit         of at most 63 octets of output from ToASCII. The design
EN> of the Punycode encoding is such that some sequences of up to 63 Unicode
EN> code points result in ToASCII output of 63 or less octets, but
EN> all possible Unicode strings of 64 code points result in ToASCII
EN> output of 64 or more octets.

d/