[idn] proposed i18n naming rules

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

Does this meet the consensus:


Internationalized domain names have the following attributes:

  sequence of labels:

      labels contain any valid UCS character code, regardless of
        whether or not a character representation is assinged to that
        character code

      character codes are explicit, not required to be normalized in
        any way

      minimum label length of 1 UCS character code

      maximum label length of 63 UCS character codes

  maximum FQDN length of 255 UCS character codes (including the
    label separators when the IDN is written out)

Internationalized host identifiers are a subset of internationalized
domain names, and have the following attributes:

  sequence of labels:

      only those UCS characters from the "safe-set"

         [version of] http://www.unicode.org/Public/UNIDATA/Scripts.txt

         U+002D (HYPHEN-MINUS)

      MUST be normalized through nameprep prior to processing

      leading and trailing characters MUST NOT be HYPHEN-MINUS

      minimum label length of 2 UCS characters

      maximum label length of 63 UCS characters

  maximum FQDN length of 255 UCS character codes (including the
    separator characters when the IHI is written out) 

  U+002E (FULL STOP) is ONLY valid for use as a separator when
    the IHI is written out

The suggestion would be that the IHI rules would apply to all encoding and
decoding systems which knew that an IDN specifically referenced a host.
This would mean applications that were issuing a lookup for the purpose of
establishing a connection, protocol operations that would use a domain
name for a host-specific function (such as message routing, HTTP HOST
headers, NS RRs in DNS where the NS explicitly referenced a host, and so
forth), and processes which decode structured data (such as email
addresses and URLs) for display.

All other IDNs would fall under the IDN rules. This includes SRV entries
in the DNS, email addresses stored in SOA and RP RRs (which can contain
FULL STOP, among others), and so forth.

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