Tonus (was: Re: Casefolding Sigma (was: Re: IDNAbis
patrik at frobbit.se
Thu Jan 31 13:43:29 CET 2008
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
(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.
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