Tonus (was: Re: Casefolding Sigma (was: Re: IDNAbis Preprocessing Draft))

Vint Cerf vint at
Thu Jan 31 14:03:39 CET 2008

thanks patrik, I failed to remember and remark that the design was  
intended to avoid having to change every name server in the world. If  
we had depended on that, the deployment would take forever and in the  
meantime things would not be uniform at all.

On Jan 31, 2008, at 7:43 AM, Patrik Fältström wrote:

> On 31 jan 2008, at 13.32, Vint Cerf wrote:
>> Patrik, in the LDH world, the upper and lower case forms are kept  
>> in the DNS database and are casefolded at matching time. In the  
>> IDN world, in part because of the complexity of the normalization  
>> process, is it correct that the design does a lot of the  
>> normalizing at registration, storing the normalized form in the  
>> database rather than the unnormalized form?
> It is a deployment issue. One could of course in IDNA2003 version  
> of IDNA have forced the normalization in three different  
> "locations" in the application/protocol:
> (a) In the application before the string touches the DNS at all  
> (including before actual storage of the domain name in the DNS  
> server at time of registration)
> (b) In the server before the actual search is done in the database  
> (so normalized strings are still only what is stored in the database)
> (c) As part of the matching algorithm so the different non- 
> normalized strings are stored in the database
> For both (b) and (c) to work, the actual software that is used for  
> DNS in the world, at ISPs, at Enterprises etc have to change. And  
> not only the one that is used by for example a DNS hosting company  
> that the owner of a domain name has chosen because of the new  
> features. But also in all caching servers that act as  
> intermediaries between the one querying for data and the one  
> serving the data.
> Because of historical empirical data on how often software is  
> updated on the Internet (which includes how long time it takes to  
> get features implemented), a decision was made that it was VERY  
> IMPORTANT that the end user, that choose to start using an  
> internationalized domain name, MUST be able to do so without  
> waiting for his domain hosting company to support it, and without  
> waiting for the ISPs that his customers used could support IDN.
> An example of slow deployment is this recent "incident" (sorry  
> again for that) with me starting using a standard from 1995 that  
> Michael Eversons (and probably many more on this list) email client  
> get confused on. That is 12 years ago.
> Another example of positive slow deployment of new features in a  
> similar way is the MIME standard in email, where the "client side  
> can upgrade before servers" was a good path. Alternative would be  
> to either have a flag day (yeah, right) or force people to wait  
> until their ISPs support the new standards. And the latter is  
> exactly what in the history Internet is NOT.
> Because of all of this, we needed an IDN standard where the  
> matching algorithm in DNS, which is byte by byte, is not changed.  
> That forces the application to do the work, and that is to do a  
> destructive mapping for different codepoints that are supposed to  
> match.
>      Patrik

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