RE: [idn] Unicode tagging

[Dan Oscarsson <Dan.Oscarsson@trab.se>]

>In fact SOA records are likely to be easy since they appear only in the
>RDATA (on the right hand side) and so don't need to be compared (so
>canonicalisation and downcasing will only be used for optimisations such as
>name compression).

The DNS standard states that case shall be preserved.
We cannot change the content of RDATA to get name compression to work.

So the best thing is if all character data "on the wire" follows the same
normalisation.

>I suggested four options earlier:
>
>1) Require that non-hostname labels remain in ASCII only.
>2) Require that protocols allow non-hostname labels to be internationalised
>with the same canonicalisation etc. algorithms.
>3) Require that protocols allow non-hostname labels to be internationalised
>with different (less restrictive?) canonicalisation etc. algorithms.
>
>4) Require that the protocol must specify which of these options (or which
>variation on one of these options) it has followed.
>
>Which do people prefer? 

2) All labels and text data should use the same format "on the wire".
Best is normalisation form C which do not destroy any data.

Canonicalisation and folding for matching is only used when doing the
matching, not "on the wire". As an optimisation one could do it
on the query name in a query but nowhere else.
When doing matching, all labels, both host names and others, will
use the same matching rules.

    Dan