Re: [idn] One profile for domain names, or many?

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

on 6/13/2002 8:16 PM Adam M. Costello wrote:

>> Clarification, the resolver doesn't "need" a flag because it already
>> has access to a flag. On the application side, this would be the Wide
>>  API versus the legacy API
>
> That works until you have a name in which some labels are non-ASCII
> text and some labels are opaque bytes.

I had to think about this some.

If any label is EDNS/UTF-8 then all of them must be flagged that way. So
if any domain names come through the legacy API then all of the labels in
that domain name are treated as STD13.

The entire domain name is what gets cached, and not the individual labels.
Therefore, if any of the STD13 labels contained eight-bit data (regardless
of whether there was ACE in any of the others) the entire domain name
would get flagged. There would not be any expansion of the other labels in
that scenario, and that domain name would always be returned as an STD13
sequence.

In the normal scenario, the zone-specific labels can't have eight-bit
character codes since those labels aren't legitimate for delegation, so
only the labels on the left edge of the domain can possibly contain
eight-bit data. This means that the scheme above won't cause problems with
any "normal" domain names (such as delegations) but would only prevent the
abnormal domain names from undergoing conversion.

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