Subject: [AAA-WG]: charset issue with draft-ietf-aaa-diameter-15.txt

From: Randy Bush <[email-masked]>
Date: Thu, 14 Nov 2002 12:20:19 -0800

From: =?ISO-8859-1?Q?Patrik_F=E4ltstr=F6m?= <[email-masked]>

Text from draft below...

When you have two strings using the Unicode Character Set, there need 
to be rules for how you compare the two strings -- if comparison is 
done.

Doing bit by bit comparison is cruel, and not recommended, but even if 
that is the solution that has to be stated.

The easiest way of doing it is to create a profile of stringprep, which 
tells how comparison is to be done, and then point at that profile in 
documents like this.

Note: UTF8String in diameter possibly have to be split in two different 
types "normalized UTF8String" and "raw UTF8String".

I am happy to explain more if needed.

     paf

>       UTF8String
>          The UTF8String format is derived from the OctetString AVP Base
>          Format. This is a human readable string represented using the
>          ISO/IEC IS 10646-1 character set, encoded as an OctetString
>          using the UTF-8 [UFT8] transformation format described in RFC
>          2279.
>
>          Since additional code points are added by amendments to the
>          10646 standard from time to time, implementations MUST be
>          prepared to encounter any code point from 0x00000001 to
>          0x7fffffff. Byte sequences that do not correspond to the valid
>          encoding of a code point into UTF-8 charset or are outside 
> this
>          range are prohibited.
>
>          The use of control codes SHOULD be avoided. When it is
>          necessary to represent a newline, the control code sequence CR
>          LF SHOULD be used.
>
>          The use of leading or trailing white space SHOULD be avoided.
>
>          For code points not directly supported by user interface
>          hardware or software, an alternative means of entry and
>          display, such as hexadecimal, MAY be provided.
>
>          For information encoded in 7-bit US-ASCII, the UTF-8 charset 
> is
>          identical to the US-ASCII charset.
>
>          UTF-8 may require multiple bytes to represent a single
>          character / code point; thus the length of an UTF8String in
>          octets may be different from the number of characters encoded.
>
>          Note that the AVP Length field of an UTF8String is measured in
>          octets, not characters.

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