MVALID (was Re: M-Label or MVALID, and dangers with mappings?)

Vint Cerf vint at
Tue Apr 14 16:16:35 CEST 2009

This exchanges has been very helpful in outlining what I think are two views
and maybe even a compromise position for the WG to consider.

Plainly we have agreed that mapping should be available to ease the
introduction of IDNA2008. We have also agreed that the canonical forms of
IDN labels (U-label and A-label that are equivalent under the punycode and
reverse-punycode mappings) are extremely valuable fixed points in the

The dialogue among Paul Hoffman, Andrew Sullivan, Pete Resnick and Patrik
Faltstrom suggests to me that a definition of Mapping (prior to lookup)
should be undertaken by the WG but that its use might  be determined by
application context. If that compromise is adopted, the Mapping would be
recommended in cases where IDNA2003 compatibility is desired/needed but that
mapping on lookup is not absolutely required under all circumstances.

If we take that path, it will be very helpful to have not only the
definition of the mapping but also advice about conditions underwhich it
seems strongly advisable to apply.


On 4/14/09, Andrew Sullivan <ajs at> wrote:
> On Mon, Apr 13, 2009 at 09:03:48PM -0500, Pete Resnick wrote:
> > IDNA 2003 can be found in [MAPPING]." What I think is not fine is for
> > the protocol document to say, "You MUST map user input with
> > [MAPPING]." That will codify a particular version of [MAPPING] that
> > may not be suitable for some cases and makes one particular user
> > input method a requirement for protocol conformance. That I don't
> > like.
> Pete's outline was so close to what I'd say that any additional
> comment from me would be gilding the lily.  So, what he said.
> a
> --
> Andrew Sullivan
> ajs at
> Shinkuro, Inc.
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