Comments on draft-ietf-idnabis-defs-10

Vint Cerf vint at
Thu Sep 3 21:22:33 CEST 2009

patch it in.

On Sep 3, 2009, at 2:15 PM, John C Klensin wrote:

> --On Thursday, September 03, 2009 06:56 -0700 Paul Hoffman
> <phoffman at> wrote:
>> At 9:23 PM -0400 9/2/09, Vint Cerf wrote:
>>> as far as I am aware, we have not modified punycode algorithm
>>> in any way.
>> At 9:24 PM -0400 9/2/09, John C Klensin wrote:
>>> I believe that it doesn't.  It restricts the input to Punycode
>>> but, so, albeit differently, do ToASCII and ToUnicode.  Do you
>>> see it doing anything else?
>> Section 4.4 says:
>>   This document updates RFC 3492
>>   only to the extent of replacing the reference to the
>> discussion of    the ACE prefix.  The ACE prefix is now
>> specified in this document    rather than as part of RFC 3490
>> or Nameprep [RFC3491] but is the same    in both sets of
>> documents.
>> That's why I put the smiley: it does modify it, explicitly,
>> but not in a noticable way.
> Well, 3492 doesn't specify the prefix.  It just refers to one,
> by reference and usually in oblique ways.  The first paragraph
> of the introduction describes an ACE but describes the ACE as
> consisting of a prefix followed by the Punycode-encoded string.
> That makes it fairly clear to me that "Punycode" doesn't include
> the prefix itself.  The references to 3490 and 3491 are at the
> end of that paragraph and just says "For the details of the
> prefix and constraints, see [IDNA] and [NAMEPREP].", a sentence
> that, in context, cannot possibly be interpreted as normative
> (and, indeed, those two RFCs are listed as informative, not
> normative, references).
> The text that follows is similarly careful and oblique about the
> prefix.
> However, if anyone really wants to engage in nit-picking about
> this (and I don't think you, Paul, do), the paragraph quoted
> could be changed to:
> 	This document does not update or alter the Punycode
> 	algorithm specified in [RFC3492] in any way.  That
> 	document does make a non-normative reference to the
> 	information about the value and construction of the ACE
> 	prefix that appears "in RFC 3490 or Nameprep [RFC3491]".
> 	For consistency and reader convenience, IDNA2008
> 	effectively updates that reference to point to this
> 	document. That change does not alter the prefix itself.
> 	The prefix, "xn--", is the same in both sets of
> 	documents.
> If anyone thinks that would be even a slight improvement, it
> would only take me a few seconds to patch it in.
>    john

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