fully-qualified domain names containing differently-encoded labels ?
=JeffH
Jeff.Hodges at KingsMountain.com
Mon Oct 25 23:51:38 CEST 2010
> On Mon, Oct 25, 2010 at 01:23:45PM -0700, =JeffH wrote:
>
>> But in any case, it would seem that any specification of conversion
>> operations on a multi-label domain name, that takes into account
>> IDNA{2003,2008}, needs to properly allow for and accomodate
>> label-by-label type diversity, yes?
>
> Given that neither IDNA2008 nor IDNA2003 had anything to say about
> domain names, but only about label names, I should hope so. You
> should treat them only by label, and not by domain name.
Understood. However, in various protocols, e.g. HTTP, one has to handle (e.g.
compare) strings matching RFC3986's "reg-name" production, and thus must
decompose said strings into labels, do the IDNA magic as necessary, and then
re-construct as appropriate and compare (for example).
> In general
> in the DNS, this is true anyway. You have no way of knowing whether
> there are actually 8-bit-clean labels inside a domain. They're
> perfectly legal under STD13, but they violate the hostname rules. If
> you're not naming a host for hostname-compatible purposes, there is
> nothing wrong with creating the label "punctuationmistake's" inside
> your domain "example.com".
>
> Moreover, note that your use of "type" there seems a little suspicious
> to me. If these were really different types in any important way, I
> would have expected rather strong arguments in favour of changing the
> xn-- prefix.
wrt the latter, fwiw, note that RFC5890 uses the terms "label type" and "label
form" essentially synonymously; and the former is explicitly used to denote
label types..
For IDNA-aware systems, the valid label types are: A-labels, U-labels,
and NR-LDH labels.
thanks,
=JeffH
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