Re: [idn] proposed i18n naming rules

["Eric A. Hall" <ehall@ehsco.com>]

Erik Nordmark wrote:
> 
> > Internationalized domain names have the following attributes:
> >
> >       character codes are explicit, not required to be normalized in
> >         any way
> 
> > Internationalized host identifiers are a subset of internationalized
> > domain names, and have the following attributes:
> >
> >       MUST be normalized through nameprep prior to processing
> 
> Looking for clue. Why aren't IDNs normalized through nameprep just
> like IHNs? What are the benefits of this?

There are no benefits per se, but penalties which are avoided. Nameprep
forbids characters which are commonly used in labels that are not valid in
hostnames (including "_" for SRV, and chars valid for LHS of email
addresses in SOA/RP), so running all IDNs through nameprep would prohibit
IDNs which are not IHIs.

http://search.ietf.org/internet-drafts/draft-ietf-idn-nameprep-06.txt

| 5. Prohibited Output

| 5.1 Currently-prohibited ASCII characters
| 
| Some of the ASCII characters that are currently prohibited in host
| names by [STD13] are also used in protocol elements such as URIs [URI].
| The other characters in the range U+0000 to U+007F that are not
| currently allowed are also prohibited in host name parts to reserve
| them for future use in protocol elements.
| 
| 0000-002C; [ASCII CONTROL CHARACTERS and SPACE through ,]
| 002E-002F; [ASCII . through /]
| 003A-0040; [ASCII : through @]
| 005B-0060; [ASCII [ through `]
| 007B-007F; [ASCII { through DEL]

I'm putting together a summary of the issues and will post it soon.

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/