DNS, UTF-8, and LDH (was: FYI: Extending IDNA to other protocols (Nick Teint))

Andrew Sullivan ajs at shinkuro.com
Wed Mar 24 17:47:07 CET 2010

On Wed, Mar 24, 2010 at 04:23:28PM +0000, Shawn Steele wrote:
> less painful, instead they’re more painful.  Maybe some older DNS
> server owners are happy, but I’ve got a lot of other unhappy places
> ☹ That includes unhappy DNS servers that handled UTF-8 prior to
> IDNA2003 and now somehow they have to reconcile the disparity.

Nothing about IDNA200x should have any effect of any sort on any DNS
server that "handled UTF-8".  DNS labels are not restricted to ASCII,
and never have been: they're octets.  The LDH rule is not a "DNS
restriction".  It's an effect of the way the hostname syntax got used
inside the DNS.

If the "DNS server" thinks that it's doing something clever with
labels to convert U-labels and A-labels transparently, it's not a
plain DNS server, but a DNS server with some other layers on top.  Or
else it's an implementation of a layer violation.


Andrew Sullivan
ajs at shinkuro.com
Shinkuro, Inc.

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