Eszett and IDNAv2 vs IDNA2008

Andrew Sullivan ajs at
Fri Mar 13 03:25:56 CET 2009

On Thu, Mar 12, 2009 at 03:34:03PM -0700, Erik van der Poel wrote:
> What about using CNAME with xd-- like this:
> ;   IN  A
>  0 IN  CNAME
>  300 IN  A

Well, actually, I'd use DNAME (because it redirects what's underneath
it -- you still have to deal with the record at the same RNAME.  But
modulo the new "xd--" prefix, you've just arrived at the "bundling"
proposal that many people seem to think will have to be good enough
for IDNA2008/IDNA2003 transition.  All you do is establish what other
records would have matched under IDNA2003 that won't under 2008, and
include them as a policy matter in the zone you're operating, making
sure they all go to the same place.  No new prefix needed.

> xd-- tells the client to do something special at display time. So does
> xn--. If xn-- gets to have special treatment, why can't xd--?

Briefly, the NS record has a well-defined semantics, and anything that
fiddles with that is, in my opinion, pretty dangerous.  But like I
said, this topic is no so far off-topic for the list that I don't want
to pursue it here.  (So if you need clarification on this point,
please send me a direct request off-list.  I won't pursue the
explanation any more here.)


Andrew Sullivan
ajs at
Shinkuro, Inc.

More information about the Idna-update mailing list