draft-klensin-idnabis-protocol-04 section 4.5

Harald Tveit Alvestrand harald at alvestrand.no
Thu Mar 27 22:56:30 CET 2008

Paul Hoffman skrev:
> At 1:17 PM +0100 3/27/08, Harald Tveit Alvestrand wrote:
>> --On Thursday, March 27, 2008 10:55:04 +0100 Simon Josefsson 
>> <simon at josefsson.org> wrote:
>>> This section reads:
>>>    The resulting U-label is converted to an A-label (i.e., the encoding
>>>    of that label according to the Punycode algorithm [RFC3492] with the
>>>    prefix included, i.e., the "xn--..." form).
>>> That assumes that no U-label will be translated into a LDH-label.
>>> In IDNA2003 some U-labels are translated to LDH-labels, for example:
>>> ToASCII(josefßon) = josefsson
>>> ToASCII(dªtªkonsult) = datakonsult
>>> Note absence of xn-- prefix and punycode data.
>>> Is the intention that these strings will not map to the same LDH label
>>> in IDNA200x?
>> As long as we keep the "no mapping" principle, the intention is that 
>> these strings will be rejected by IDNA200x.
> I fully disagree with Harald, and this is fundamental to the 
> definition of the protocol. Those strings would be rejected if the 
> application did not do sufficient mapping before doing a lookup as 
> specified in Section 5.3. An implementation that wants to interoperate 
> with IDNA2003 for labels that were mapped in IDNA2003 would do some 
> mapping.
I think we agree, actually.

The intention is that these strings will be rejected by IDNA200x (as 
defined in the current 4 documents). IF it gets that far.

If it gets converted to something else before it gets to IDNA200x - it's 
that other string that IDNA200x will accept or reject. But that's 
out-of-scope for IDNA200x.

More information about the Idna-update mailing list