Subject: Re: [nfsv4] [FedFS] Meeting Minutes, 4/15/2010

From: "David Harrington" <[email-masked]>
Date: Tue, 20 Apr 2010 22:16:56 -0400

Hi,

<speaking as individual contributor>

I think "just use UTF-8" might be simplistic (but I am not an expert
in UTF-8 or newprep).

stringprep is used for LDAP and IDN.
stringprep may bar usage of some (now) valid utf-8 domain names. 
newprep updates stringprep to recognize newer versions of Unicode.
implementations that use stringprep and implementations that use
newprep will return different results when comparing strings, if
certain now-valid utf-8 characters are used, or certain now-invalid
assumptions are used to prepare the strings for comparison.

Below is a discussion of the impact of newprep (relative to iDN and
SCSI; I think the problems faced by NFSv4 might be similar).

dbh

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of [email-masked]
Sent: Thursday, March 25, 2010 2:41 AM
To: [email-masked]
Subject: [storm] More on the newprep BOF

Reminder - Look for newprep BOF materials here:
https://datatracker.ietf.org/meeting/77/materials.html

This are the rest of my notes from the newprep BOF on Tuesday. 

A major motivation for moving beyond stringprep is that stringprep is
fixed at Unicode 3.2 (the current version of Unicode is 5.2).
Characters added to Unicode versions subsequent to 3.2 are usually
prohibited by stringprep because the stringprep tables treat their
Unicode codepoints as unassigned.

In addition, there are problems in the original specification of
stringprep that require changes to the processing of four Unicode
characters:
	1) The eszett (sharp s) character in German (already discussed
on this list).
	2) The sigma character in Greek when it occurs at the end of a
word.
	3&4) The zero width joiner and zero width non-joiner
characters.
These changes will show up in domain names, and hence impact IQN names
for iSCSI

The two zero width characters are apparently crucial to Persian
(Farsi) text.  We may need some help in determining whether/how that
crucial role carries over to iSCSI IQN names.  If there's someone on
this list who is fluent in written Persian (Farsi) and is familiar
with iSCSI IQN names, please send a quick email to Tom
([email-masked]) and I ([email-masked]), as we may want to
call upon your expertise at some point in the future.

But wait ... there's another (bigger, IMHO) problem.  iSCSI names are
always lower case, and stringprep is used to realize a Unicode version
of tolower().  The current approach to domain names (IDNA2008) has
abandoned case folding (e.g., convert to lower case), as there are
apparently languages in which it is not as simple as tolower().  In
Unicode terms, this is a side effect of domain names changing from
normalization form KC (NFKC) used by stringprep to normalization form
C (NFC).

I want to emphasize that this is at an early stage, and it looks like
we're going to get some help from the newprep effort.  My sense of the
conclusion of the newprep BOF is that there was strong support to form
a working group to do something about the problem, but very little
sense about exactly what the new WG should do; watch for a proposed
charter to emerge before the Maastricht meeting week.

Anyone interested in following or further participating in this
adventure should join the [email-masked] mailing list:
https://www.ietf.org/mailman/listinfo/newprep

Thanks,
--David
----------------------------------------------------
David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email-masked]        Mobile: +1 (978) 394-7754
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---

From: "David Harrington" <[email-masked]>
Date: Tue, 20 Apr 2010 23:18:04 -0400

Ah, the problems inherent in reading emails in reverse chronological
order, and responding before getting through the backlog ... ;-)

I see members of the WG have significant experience in this area.
I think I'll just shut up now, and learn from others ...

dbh

> From: [email-masked] [mailto:[email-masked]] 
> On Behalf Of David Harrington
> Sent: Tuesday, April 20, 2010 10:17 PM
> To: [email-masked]
> Subject: Re: [nfsv4] [FedFS] Meeting Minutes, 4/15/2010
> 
> Hi,
> 
> nfsv4 mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/nfsv4
>