Subject: Re: [idn] lowercased hostnames (was: naming syntax rules)

From: Dan Oscarsson <[email-masked]>
Date: Tue, 11 Dec 2001 14:10:51 +0100

>This is pretty much the scope of the problem: does mandatory lowercased

>hostnames in these streams break existing systems?

As DNS have set the good example of having domain names to be
case-insensitive,
it is the applications that should follow this. Unfortunately many
applications today
do not. This is why I want at least PTR records to retain case.

The main reason, that I know of, that some want to require lower case
names
is to fix so that we do not have to require the DNS server to know how
to
compare names case-insensitivly. This is needed for a IDNA solution but
not for a server based. While I do not think case-insensitive matching
in server will be to CPU expensive (guranteed not if you only have
case-insensitivity (there are not very many letters that have case)),
the
middle ground that could be used is to require queries to the DNS server

to use the "compare form-insensitive" form but that all responses retain

original case. This way no vital data will be lost.

What I can see the names encoded in ACE for IDNA must be
not just lower cased but also have all the transformations done
on the characters without case, that we will define to match as equal.
Otherwise IDNA will not work.
But for solutions using native UCS (in the form of UTF-8) in the DNS
protocol, we can allow DNS to work like today matching names
case-insensitively.

   Dan

---

From: "Eric A. Hall" <[email-masked]>
Date: Tue, 11 Dec 2001 22:44:03 -0600

Dan Oscarsson wrote:

> What I can see the names encoded in ACE for IDNA must be not just
> lower cased but also have all the transformations done on the
> characters without case, that we will define to match as equal.

Right.

> protocol, we can allow DNS to work like today matching names

Isn't this mutually-exclusive? If the hostname is defined with UCS
characters of mixed case, then the PTR will have to always provide that
case form, but ACE will not be able to provide the PTR data in mixed case.
Therefore, ACE will always break the PTR if a hostname is defined in mixed
case. And if people are allowed to define mixed case (the canonical UCS
form works), then they will always be getting shafted by ACE PTR RRs.

It seems that if we are forced to lowercase everything but ASCII for ACE
then we have to always lowercase everything but ASCII regardless of the
encoding that may or may not be used.

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