Potential Erratum re. length limits in RFC 5890

John C Klensin klensin at jck.com
Tue Sep 28 16:21:31 CEST 2010

--On Tuesday, September 28, 2010 14:47 +0100 Slim Amamou
<slim at alixsys.com> wrote:

> 2010/9/28 John C Klensin <klensin at jck.com>
>> (...)A 63 user-abstract character limit is an upper limit
>> that is unlikely to be reached if non-ASCII characters are
>> present (impossible in the Unicode encoding),
> Could you please clarify this a little more?

Maybe not, and certainly not today (I've got other priority
commitments).   As editor, I was on the losing side of part of
the argument about whether there should be a hard restriction on
the length of U-labels.  As a result, I wrote down exactly what
the WG told me to write down, without making creative
substitutions of words, correct or not.  And I remember a lot of
WG tuning of that particular language.

I really wish we could have had this conversation while the
document was still open.  At this stage, even if we decide the
text is not optimal, the issue is not a simple erratum in which
"octet" was substituted for "character" by some editing accident
-- the only real option is to create a reminder for coming back
to the issue if the document is ever revised.

I'll try to come back and review the relationships when I have
time but, again, it won't be today.   The good news is that it
really doesn't make any difference: the text rather clearly
states that 252 character number as guidance that U-labels can
get a lot longer than A-labels rather than as a normative


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