Re: [dnsext] draft-yao-dnsext-identical-resolution-02 comment

[Masataka Ohta <[e-mail]>]

Vaggelis Segredakis wrote:

> As the Greek registry, offering registrations in Greek characters presented
> the problem with the accent mark "tonos" which is used in the majority of
> Greek words. In capital letters however, the same words are spelled without
> the tonos.

The problem already occurs in ISO 8859/1 with 'y' with diaeresis,
upper case of which is plain 'Y' without diaeresis.

> Their representation in the Punycode is unfortunately different
> and we had to match these up (make similar) for the user,

Definitions, such as case correspondence, in Unicode are not definitions
useful in the real world, which means Unicode is
useless.

> We used the DNAME mechanism with not very satisfactory results.

Suppose you have a label:

	YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY.com

You can match it with:

	YyYYYyYYYYYYyYYYYyYYYYyYYYyYYyYYYyYYYYYyYYyYYyYyYY.com
easily because case correspondence is recognized by DNS protocol.

But, if you want to do the same thing with 'y' with diaeresis,
you can't do it with predefined BNAME/CNAME/DNAME, because of
exponentially many aliases.

However, dynamic generation of *NAME causes performance problem
with secure DNS.

So, you should give up localized DNS, secure DNS or have common
definition on extended case insensitivity (not really defined
in Unicode) between DNS servers and (security aware) clients.

My recommendation is to give up both.

> This way we cannot have consistent mappings since we do not know
> what the programmer has chosen to do with the upper case
> characters, especially in regards to tonos and final sigma.

For precise definitions of extended case insensitivity, we need
a formal language for extended case insensitivity description.

Locale dependent case insensitivity for localized domain names
requires locale information somehow supplied through DNS.

						Masataka Ohta
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