Re: [idn] Alternative Solutions

["Adam M. Costello" <amc@cs.berkeley.edu>]

Edmon <edmon@neteka.com> wrote:

> Server-side ACE - ACE transformation takes place at server end

If it's on the server, it doesn't have to be an algorithmic
transformation; it can just be a distributed lookup table (which is what
DNS is anyway).

Two new resource record types could be created, one that gives the
Unicode domain name associated with an LDH (letter/digit/hyphen) name,
and one that gives the LDH name associated with a Unicode name.  This
is analogous to the A and PTR records that map between LDH names and IP
addresses in both directions.

Example scenario:  I type a Cyrillic email address into my IDN-aware
email program.  It performs nameprep and sends the result in a DNS
query using a canonical encoding (UTF-16 say).  It gets back both an IP
address (which it uses to connect to the remote SMTP server if there is
no MX record) and an LDH domain name.  It puts the LDH name in the To:
field of the message header, in order to conform to RFC 822.

Suppose the message is sent to multiple recipients.  They can all reply
to everyone in the To: field, because the domain names there are LDH
names.  Additionally, IDN-aware mail programs can do a DNS lookup on the
LDH domain names to discover the corresponding Unicode domain names, and
show the latter to the user.

I don't think this requires any changes to the DNS protocol, only the
addition of two new resource record types.

I don't like this idea as much as ACE, for two reasons:  First, the
mapping between LDH names and Unicode names cannot be done offline.
Second, there is no guarantee that the mapping is consistent in the
two directions (just as there is currently no guarantee of consistency
between A and PTR records).  It has one advantage over ACE, though:  The
LDH names can be chosen arbitrarily, and need not look like gibberish.

AMC