Subject: Re: [Sip] Last Call comments on 2543bis-07

From: William Marshall <[email-masked]>
Date: Mon, 4 Feb 2002 19:22:01 -0500 (EST)

Henning Schulzrinne wrote:
> Robert Sparks wrote:
> > This class of requirement is obviously on future specifications, not
> > implementations. As such, you could argue that they belong in the
> > guidelines draft. I would have no problem moving the three examples you
> > present here, but I get the feeling that this isn't a complete list. Is
> > requirements on future extensions the _only_ class of requirements
> > giving you trouble?
> 
> My suggestion is that all of them should move into or close to the IANA
> sections, since they are needed by things that need IANA registration in
> any event. The section can then be prefixed by a "this is for specifying
> compliancy of protocol designers, not implementations" (obviously, not
> worded that way...)

This suggestion works fine for me.  I'd then re-word the lines where
the spec words now appear as simple statements of fact, e.g.. "All
new header fields follow this generic format..."

And, that is the _only_ class of requirements giving me major trouble.
There was a second class of requirements that I mentioned previously,
(though not enough to raise in my email this morning).  Several places
in the draft are spec words about inter-layer communication in the
reference design.  For example, line 2335 says "UAS core ... MUST pass 
[the 2xx response] to the server transaction for transmission."  I
believe normative language about retransmission of 2xx responses to
non-INVITEs is covered elsewhere, and this could be re-written as
"UAS core ... passes [the 2xx response] to the server transaction..."
and thus avoid specifying the reference design as a MUST.  I'll
leave these to the editor's discression.

Bill Marshall
[email-masked]

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From: Henning Schulzrinne <[email-masked]>
Date: Mon, 04 Feb 2002 19:21:48 -0500

I agree that having a MUST or SHOULD in simple behavioral statements
just makes the text hard to read and monotonous. This is a fine line to
walk, since some people would want every sentence with a verb to have a
MUST before the verb. I tend to think of MUST and SHOULD as emphasis,
where it is likely that an implementor will do something different if
left to her own devices, rather than just describing routine behavior.
Others likely disagree.

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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 05 Feb 2002 12:22:13 -0500

> left to her own devices, rather than just describing routine behavior.

Indeed, we've gotten burned before because non-normative statements
meant people weren't clear what to do. In the case of these kinds of
statements below, the interpretation of "MUST send to layer X" is really
"MUST follow the procedures specified in section XX from here on". 

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 05 Feb 2002 12:25:41 -0500

> new header fields follow this generic format..."

IANA is not going to look at this, I suspect. I dont think it is their
job to check that extensions follow particular BNF patterns.

I suspect the right thing might be to move such things into
draft-ietf-sip-guidelines. Indeed, the particular bit about generic
header formats is already in there. That document would serve as the SIP
working groups measuring stick when reviewing drafts (preferably in
advance of wglc). 

Anyone object to moving these types of references there? We'll need a
volunteer to do a clean sweep of bis to find them all.

-Jonathan R.