Re: [idn] IDN character repertoire, nameprep

[Johnny Eriksson <bygg@cafax.se>]

"Adam M. Costello" <amc@cs.berkeley.edu> wrote:

> It has occurred to me that nameprep is currently moving two distinct
> tasks from the DNS servers to the applications, when perhaps only one of
> those tasks should move.  The two tasks are:
> 
>  1) Finding equivalences, for example, ABC.com == abc.com.
>  2) Prohibiting some names, like a+b.com.
> 
> Currently, most applications do neither.  For example, ping is happy
> to send all three of those names, exactly as shown, to the DNS server.
> The DNS server performs canonicalization on each lookup, and performs
> prohibition when it loads the zone file.
> 
> Both tasks become more expensive for IDNs.  Since canonicalization must
> be done on each query, it makes sense to move it to the application.
> But since prohibition is done rarely, I think it should remain the
> job of the DNS server.  That way, if more characters are added to the
> allowed set, it is not necessary to upgrade applications, but only to
> upgrade the DNS servers, and it's only the servers for domains that
> wish to register names containing the new characters that need to be
> upgraded.

In order to prohibit characters, the DNS server has to undo the ACE
encoding.  You have just started to modify DNS, something that many
people try desperatly to avoid.

> AMC

--Johnny