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

[bill@mail.nic.nu (J. William Semich)]

My view: "form-folding" will be required on the application level, yes. but
it is not for certain all applications will do it, or do it
appropriately/authoritatively.

The question between 1 and 2 below is, where will the "authoritative"
folding/canonicalization take place? IMO, DNS servers should be the
authoritative point of reference, as they will continue to be for ASCII
case-insensitivity. Implementation tests can show how much impact this will
have on CPU resources.

Bill Semich


At 09:04 AM 7/21/00 +0200, 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
>
>
>
Bill Semich
President and Founder
.NU Domain Ltd
http://whats.nu
bill@mail.nic.nu