Comments on draft-ietf-idnabis-defs-10

Andrew Sullivan ajs at
Tue Sep 1 18:08:09 CEST 2009

On Tue, Sep 01, 2009 at 11:10:27AM -0400, Vint Cerf wrote:
> andrew, the problem with that last point is that the two labels will  
> match in DNS but produce different U-label on conversion. I think that  
> is not a good outcome.
> downcasing would solve that wouldn't it?

I am really reluctant to add a normative downcasing step anywhere,
because it's a very late change to the protocol.  I can't think of
anything it would break, but I didn't think of this problem before,
either, and mostly nobody else did either.  I'd have grave concerns
about adding another normative step to the protocol during WGLC, and
then sending the result on to the IESG.

The important thing we have exposed in this discussion is that there
are _several_ possible matches in the DNS to a given valid U-label,
but exactly one of those candidate DNS matches is itself a valid
A-label.  That suggests that saying, "making sure you downcase before
converting the U-label is probably a good idea," may be enough --
roughly what John suggested, I think, but I'm not totally sure.  We
first need to resolve the discussion of uppercase/lowercase form from


Andrew Sullivan
ajs at
Shinkuro, Inc.

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