Re: [idn] UTF-8 / RACE

["Eric A. Hall" <ehall@ehsco.com>]

> still, I don't see any harm in having a native UTF-8 DNS query
> interface if we can achieve the following:
> 
> - delegation paths for UTF-8 are the same as for ACE
>   (queries for equivalent names go to the same servers)
> - results of a query are consistent between the two encoding schemes
>   (a query of one type made to a server produces equivalent results
>   - modulo encoding - as a query of the other type)
> - success/failure semantics are the same for the two
>   (if a query using one encoding succeeds or fails, the same
>   should be true for the same query using the other encoding)
> - delay characteristics are similar for the two

This is doable with the following scenario:

 - UTF8 is only sent in new EDNS message.

 - ACE is only sent in legacy message.

 - Server returns answer data based on query message format.

In that model, the answers that the client gets back depends on the query
that they send. Both sets of answers are sourced from the same server so
there is no divergence. Zone data would be managed in the UTF8 form, and
ACE conversion equivalents would be generated by the servers, thereby
providing consistency at the source.

There are a few other issues here:

 - There needs to be a wide() version of gethostbyname and the
   like so that clients can make the right calls depending on
   their application support.

 - Queries have to go to the UTF8 server or its cache, which
   means that the authoritative servers for the zone have to
   be upgraded. As to the size of this as a problem, I put it
   in the same camp as IMAP-v-POP: if you want IMAP on your POP
   server, upgrade.

   Note that this does not affect queries for remote zones,
   since ignorant queries would be in legacy form, and would
   be therefore answered in ACE form. Only the authoritative
   servers for the zone need upgrading.

 - Caches will not always be completely synchronized, since an
   ACE query may arrive two hours before a UTF8 query, and the
   data may have changed in the meantime. I don't consider
   this to be a propblem since cache integrity is not assured
   currently. But it may be excessively confusing to have two
   users issue the same query and get different answers.

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/