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Re: [idn] Re: 7 bits forever!
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Valdis.Kletnieks@vt.edu wrote:
> Those who think the DNS is being overly strict in enforcing ASCII in
> domain names are invited to consider the following:
>
> 1) RFC1035 says this in section 3.1:
>
> Although labels can contain any 8 bit values in octets that make up a
> label, it is strongly recommended that labels follow the preferred
> syntax described elsewhere in this memo, which is compatible with
> existing host naming conventions.
That's a recommendation about what names should be chosen for hosts,
*not* about what names should be accepted by applications in domain name
fields. If the purpose of RFC 1035 and RFC 2181 allowing 8-bit was not
that at some point the 8th bit would be *used*, then what on earth was it?
> Name servers and resolvers must
> compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
> with zero parity. Non-alphabetic codes must match exactly.
>
> RFC2181, section 11, re-iterates that the DNS is codeset-agnostic.
>
> So what do you know... the DNS spec is already using an N-bit-clean
> length-data encoding. So obviously there's some Very Evil Restriction
> that makes it not allow non-ASCII. And the favorite whipping boy here
> is BIND, which by default restricts it (you can put 'check-names off;'
> for a zone in the named.conf file, and you can put 'options no-check-names'
> in your resolv.conf).
>
> 2) Why does it get restricted? Consider the parsing issues involved if you
> have a domain name that uses raw Unicode and embeds the character
> known as "Malayalam Letter UU". A hint why this is Very Bad are available
> at http://www.unicode.org/charts/PDF/U0D00.pdf
What are you talking about? There's nothing about U+0D0A that makes it
any different from any other character (hint: its UTF-8 encoding is *not*
0x0D 0x0A, if that's what you meant).
- --
David Hopwood <david.hopwood@zetnet.co.uk>
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