[idn] Planning ahead for good IDNs

["D. J. Bernstein" <djb@cr.yp.to>]

There seems to be widespread agreement, even among ACE proponents, that
we will _eventually_ move to UTF-8 domain names.

This means that some programs will have to be upgraded. Obviously we
should be warning people _now_. Let's publish an RFC pointing out that
these programs will have to be fixed.

We can also prevent any long-term length problems by recommending that
programs allow 255-byte local parts and 255-byte domain names.

---Dan

P.S. I'm not trying to suggest ACE-now-UTF-8-later as an IDN compromise.
A direct move to UTF-8, with nameprep isolated in the user interface as
I described, will give us a smoothly functioning IDN system within a few
years. ACE will cost much more, because many more programs will have to
be replaced; even after the subsequent move to UTF-8, it will take years
to eradicate all the annoying ACE displays.