Re: [idn] conflicts with ACE and STD13

[Dan Oscarsson <Dan.Oscarsson@trab.se>]

>The distinction between host names and domain names is subtle and 
>hotly contested in the DNS world. The IDN WG is only dealing with 
>host names, for now. This demarcation between these two has not been 
>very important before now, but IDN is making it important.

The current DNS standard defines that a domain name is
a sequence of octets with the octets corresponding to ASCII
are to be treated as ASCII.
It does not define how the non-ASCII octets are to be handled
(except as binary values), but they are allowed everywhere.
It is correct DNS today to have a domain name in UTF-8 or
ISO 8859-1. Both represents the ASCII characters as ASCII
which is the required part.
Some of the domain names containg UTF-8 or ISO 8859-1 can
be host names. They are still valid names, it is just some
applications that reject them. DNS may not reject them.

But encoding domain names as IDNA does with an ACE can
result in breaking backward compatibility and the
current standard.
A name with some ASCII and some non-ASCII characters will
in ACE all be transformed into something else, but using
UTF-8 it will have all ASCII characters as ASCII as the
standard says.

Backward compatibility means that existing usage should not break.
For those who only see DNS as just ASCII today, then using
UTF-8 will not break anything that works today.

   Dan