Re: [idn] Determining equivalence in Unicode DNS names

["Edmon" <edmon@neteka.com>]

Hi Stuart,

I think the current argument is "buyer beware" and pepsi will have to make
sure they get all the variances.  You are right that individual
authoritative servers will have to make their own equivalence rules if they
want to.  But your example is even not as extreme as when I mentioned
earlier that <capitalALPHA>.com will look exactly like A.com but currently
they are different domains.  So a zone operator will have to implement some
equivlance rules themselves.

Further to your suggestion, I think the use of DNAME is quite interesting.
In fact it could be used in the future for migration towards a UCS system
perhaps based on EDNS.  The server will have

pépsi.com.                 IN      DNAME   xx--aceofpépsi.com.
xx--aceofpépsi.com.  IN      NS      dnsauth1.sys.gtei.net.
dnsauth1.sys.gtei.net.  IN      A       4.2.49.2

Is this not also a possible way to move toward a UCS system?  with this,
future clients dont need to deploy ACE at all, but will obtain the
information from the server.
Edmon

----- Original Message -----
From: "Stuart Cheshire" <cheshire@apple.com>
It seems to me that the solution is to give up on the idea of a single
global set of rules, and instead let each name server be authoritative
for the equivalence rules for the zones for which it is authoritative. If
a client tries to look up "www.pépsi.com.", and the "com" name servers
have been configured to treat "pépsi" as equivalent to "pepsi", then they
return the answer for "pepsi.com.", and in the reply they also include a
(programatically generated) DNAME record which *tells* the client and any
intervening caching resolvers that these two names are equivalent:

pépsi.com.              IN      DNAME   pepsi.com.
pepsi.com.              IN      NS      dnsauth1.sys.gtei.net.
dnsauth1.sys.gtei.net.  IN      A       4.2.49.2

This way we don't need to have a global flag day, because as servers are
updated to support international domain names, they can "educate" old
clients as they go, using DNAME. If we find that text equivalence rules
evolve over time to meet changing needs that's fine too, because the
servers can be upgraded one at a time as the user's needs demand that.
Clients and caches don't need to know any of the equivalence rules at
all; they just need to obey the DNAME mappings that they are told.

Stuart Cheshire <cheshire@apple.com>
 * Wizard Without Portfolio, Apple Computer
 * Chairman, IETF ZEROCONF
 * www.stuartcheshire.org