In message <558a39a60903110907i6edad88dye59293cbac951...@mail.gmail.com>, James
Seng writes:
> Agreed :)
>
> DNS is suppose to be 8-bit clean as according to RFC 1035.
No it is supposed to be nearly 8 bit clean. :-)
> But taken in context with that recommended section in RFC 1035, together with
> RFC 952, many legacy implementation already assumed DNS must be LDH.
> By the time RFC 2181 comes along, it was too late.
>
> This was one of the reasons why Punycode was chosen and not UTF-8 for IDN.
>
> -James Seng
RFC 952 is for HOST NAMES
RFC 1035 is for DOMAIN NAMES.
Host names and domain names are DIFFERENT things and are
often confused in the RFC's.
Punycode was choosen because the hostname lookup components
of resolvers and other components in applications enforce
LDH for HOST NAME lookups (forward and reverse) and for MX
lookups. Other sorts of lookups were not constrained.
Host names and mail domains restrictions come from outside
of the DNS.
IDNA sits on top of RFC 952 (modified by RFC 1123) which
sits on top of the DNS.
> > Er, that's in Section 2.3.1: Preferred Name Syntax which says before the
> > BNF:
> >
> > "The following syntax will result in fewer problems with many
> > applications that use domain names"
> >
> > RFC1035 does not say that labels can only be composed of ASCII letters and
> > digits. RFC1123 imposes limitations on the characters permissible in a host
> > name. But that's not the same as a domain name.
> >
> >
> > PS Apologies for changing the Subject: header into something appropriate.
> >
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--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: mark_andr...@isc.org
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