RE: [idn] stringprep comment 1

[Paul Hoffman / IMC <phoffman@imc.org>]

At 9:56 AM -0800 2/1/02, Yves Arrouye wrote:
>The interesting scenario is: Server S is on Nameprep-08 (where a deletion
>mapping has been introduced for codepoint U+XXXXX), Client A is on
>Nameprep-07 but his OS supports Unicode 4.0 and its IME generates U+XXXXX.
>Client A will then pas U+XXXXX unchanged (since it was unassigned when
>Nameprep-07's tables were generated) and Server S won't find a match, since
>its stored strings do not have U+XXXXX.

That scenario will happen, and it is *supposed* to happen. It is 
identical to if Nameprep-08 mapped U+XXXX to U+XYZX. The client must 
not get a positive response to a query that includes characters that 
are not allowed in the version on the authoritative server.

>  Same for case mapping, if that were
>to happen. The user has no clue what is happening to her.

Correct. It is identical to a user accidentally entering a Greek 
capital Alpha instead of a Latin capital A. Or, even if we didn't do 
IDN, the user accidentally enters numeral 0 instead of Latin capital 
O. The DNS matching scheme will simply say "no match". In other 
words, these failure scenarios are not a criticism of the versioning 
method, they are a criticism of the simple matching in DNS.

--Paul Hoffman, Director
--Internet Mail Consortium