Re: [idn] Where to do form-folding?

[RJ Atkinson <rja@inet.org>]

At 05:26 21/07/00 , James Seng wrote:
>Before anyone goes too far down this track, I would like to remind
>everyone that IETF only concern on the data on the wire (see the big box in the requirement I-D) and not the implementation detail.

James,

         The note below is clearly well inside the IETF scope.
The specification for the data on the wire is significantly different 
if the DNS resolver/client performs normalisation than if
the DNS server performs normalisation.

         So the entire discussion below is entirely appropriate
for IETF IDN WG and entirely within scope of this list and
this WG.

Regards,

Ran
rja@inet.org

>Having said this, let me think about this and will comment something
>later :)
>
>-James Seng
>
>Dan Oscarsson wrote:
> > 
> > Hi
> > 
> > Even if it is summer, some of you are hopefully still active. At
> > least some of you going to the IETF meeting.
> > 
> > Here is one thing we could discuss and that could be discussed
> > at the meeting.
> > 
> > The question is: Where should form-folding be done?
> > 
> > Background: With ASCII names names are compared case-insensitively.
> > One way to do the comapring is to first case-fold and then binary compare.
> > When we have IDNs, case-insenstivity is not enough. Instead I will call
> > it form-insensitivity, which includes case-insensitivity and insensitivity
> > to many other forms used in non-latin alphabets. To compare to IDNs
> > you can first form-fold them and then binary compare the names.
> > Form-folding is another name for all the normalisation, lower casing,
> > canonisation and simplifying described in for example the NAMEPREP draft.
> > Does anybody have a better name?
> > 
> > Places to do form-folding:
> > Below I give what I think are the two most important places and the most
> > important good and negative points for them. There are more points.
> > 
> > 1) Form-folding is done only in the DNS servers.
> >    + Only authorative servers need to implement it.
> >    + Only the folding for the authorative subset of UCS need to
> >      be implemented.
> >    + Less places where form-folding need to be implemented.
> >    - Higher CPU demand on servers.
> > 
> > 2) Form-folding is done in resolver (and servers when zone loading).
> >    + Less CPU demand on servers.
> >    - More places where form-folding need to be implemented.
> > 
> > 
> > In my draft I use 1), others have 2) instead.
> > I have thought that the good points of 1) makes it the best choice. Also
> > some drafts saying 2) would not fullfill any requirements good enough.
> > But a few days ago I thought about one more aspect that might make
> > 2) the best choice:
> > 
> > There are many applications that compare hosts or domain names.
> > For example: sendmail and many browsers.
> > These applications should also compare IDNs as equal in the same way
> > that DNS does. This means that they also need to implement form-folding.
> > If the resolver libraries include the standard implementation
> > of form-folding (and name comparing), and had the API public, all
> > applications could use it instead of implementing their own.
> > 
> > So by choosing 2) we can get the additional benefit of supplying
> > a standard place for applications to the routines to do
> > form-folding and IDN comparing. And thus reducing the risk of many
> > implementations, some that will do it wrongly.
> > 
> > Thats it. What do you think? Am I missing some important aspects to
> > make the best choice? Maybe it is something that could be
> > discussed at the meeting.
> > 
> > Regards,
> > 
> >   Dan