Re: [idn] question about cidnuc

[Paul Hoffman / IMC <phoffman@imc.org>]

>   Since your doc. describes two modes for compressed string and
>one case without compression (actually one octet explansion),
>I thought there would be three cases.

The draft only describes two modes, and gives an exact method for 
determining which is used for any domain part. If you follow the steps 
exactly (and you must do that to assure that there is only one 
representation of any domain name part), there should be no ambiguity.

>   I would say that your document could be improved for easier reading.
>You could also include simple examples, which will help readers a lot.

Examples is a very good idea. I'll add that to a future version.

> > In downcasing UTF8,
>
>1. ?? I know UTF-8, but not "downcasing" UTF-8.
>Could you please give me some reference for downcasing.

Sorry for the oblique reference. I was referring to the 
<http://www.imc.org/draft-oscarsson-i18ndns> draft that had been mentioned 
on this list earlier. Since none of the proposals for IDN are at all 
official in this group, the terms do get confusing.

> > in UTF-5, it is 15 characters;
>
>3.  I guess I can figure it out.
>In UTF-5, one Hangul jamo (two octects) will become four octets.
>Therefore, the limits seems floor (63/4)=15.  Am I right?

Correct.

> > in cidnuc, it is 37 characters.
>
>4.  I am somewhat confused here.
>In case of one-octet header, the limit seems 36 chars, not 37 chars.
>Please corret me if I am wrong.  My calculation is shown below:
>
>   1) let's assume we have 37 jamos (=74 octets).
>   2) after compression, we have 38 octets (due to 0x11 header).
>   3) after base32 encoding, we have
>     ceiling (38*8/5) = ceiling (60.8) = 61 octets.
>   4) after prepending "wg4", we have 64 octets, which exceeds 63 by one.
>
>Therefore, the limit seems 36 chars.

Whoops! Your math is better than mine. Yes, it is 36.

>5. In the document, it is said that
>   "the two-octet mode limits the number of chars to 17".
>
>I am somewhat confused here too.  The limit seems 18, not 17.
>Please corret me if I am wrong.  My calculation is shown below:
>
>   1) let's assume we have 18 chars (=36 octets).
>   2) after compression, we have 37 octets (due to 0xd8 header).
>   3) after base32 encoding, we have
>     ceiling (37*8/5) = ceiling (59.2) = 60 octets.
>   4) after prepending "wg4", we have 63 octets.
>
>Therefore, the limit seems 18 chars.

Again, you are right. My numbers were from a different algorithm that I had 
used earlier. Thanks for correcting this!

--Paul Hoffman, Director
--Internet Mail Consortium