Making progress on the mapping question

Vint Cerf vint at
Tue Mar 31 18:02:36 CEST 2009


precision is definitely called for.

John Klensin also asked whether the mapping step is a permanent part  
of IDNA2008 or whether it is a transitional step that is eventually  

Another question, as you point out, is exactly what mapping to perform  
whenever mapping is determined to be appropriate.

A third is when should the mapping occur.

Under IDNA2008, symbols like <heart> would not be ALLOWED characters  
as I understand it.

One of the reasons for accepting the idea of mapping in the compromise  
reached at IETF74 is accommodation for backward compatibility but it  
was less clear whether the consensus was for a permanent presence for  
a mapping function or a phase-out period of some kind after which the  
more strict rules of the current IDNA2008 would apply.

I think it would be useful to set up discussion threads around these  
questions so I will send out three messages attempting to do that.


Vint Cerf
1818 Library Street, Suite 400
Reston, VA 20190
vint at

On Mar 31, 2009, at 11:15 AM, Paul Hoffman wrote:

> One of the things that a few people said at the mics last week was  
> that we need to be much more specific about what we mean when each  
> of us says "mapping".
> At 7:41 AM -0400 3/30/09, Vint Cerf wrote:
>> 1. first look up under IDNA2008 rules
>> 2. If a domain name is found, return the corresponding results
>> 3. If a domain name is not fund, apply IDNA2003 mapping
>> 4. If a domain name is found, return the results
>> 5. If a domain name is not found, report that no such domain name  
>> exists
> Take i<heart> A fairly reasonable definition  
> for "mapping" in step 3 is "follow the steps in RFC 3490 for  
> ToASCII". If so, in step 4 that domain name will return positive.
> At 9:17 AM -0400 3/31/09, Vint Cerf wrote:
>> We are not going to revisit this for the Nth time. The WG long ago
>> concluded to drop these symbols from IDNA2008 and nothing has  
>> changed.
> That sounds like you emphatically do not want step 3 to return  
> positive for i<heart> Thus, you (and each of  
> us) need to give a more complete definition of "mapping".
> On a related note, Mark's proposal from yesterday defines mapping  
> quite precisely, but does not follow the steps above because the  
> mapping is done before what you have as step 1. So, the WG needs to  
> decide both what it means by "mapping", and when that will be applied.
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