Document: draft-ejzak-sipping-p-em-auth-03.txt
Reviewer: David L. Black
Review Date: 27 May 2007
IETF LC End Date: 28 May 2007
IESG Telechat date: unknown

Summary:
This draft is basically ready for publication, but has nits
that should be fixed before publication.

Comments:

The draft is in generally good shape.  Most of these comments
are minor, with the exception of the confusion in Section 4
about whether the motivating problem scenario is SIP-to-SIP
vs. SIP-to-PSTN vs. SIP-to-SIP-to-PSTN (I think it's the
latter, but I'm not sure).

1.  Introduction

Something is wrong with this text describing the use of the
P-Early-Media header:

	... to authorize the 
   cut-through of backward and/or forward early media. The P-Early-
   Media header is intended for use in a SIP network, ...
   that prohibits the exchange of early media 

"prohibits" reads as an absolute prohibition.  It should be
changed to "otherwise prohibits", "prohibits by default", or
something similar to avoid the implication that the prohibition
is absolute.

2. Applicability Statement 

Please explain or cite a reference for the term "parallel forking".

3. Conventions and Acronyms

Some of the acronym expansions ought to cite sources for the
concept involved (e.g., ABNF is specified by RFC 4234).

4. Background on early media authorization 

This section (up to the start of 4.1) seems to be somewhat
confused about whether the problem being described is a SIP-to-SIP
problem vs. a SIP-to-PSTN problem.  Most of the text is about
the latter, so I suggest focusing on that and leaving the
SIP-to-SIP material to the end of the section.  OTOH, it may
be that the actual problem structure is SIP-to-SIP-to-PSTN, in
which case that is not at all clear from this text, and a
diagram may be in order for clarity of exposition.

9. Formal syntax

Add a note that not all combinations of multiple em-param
elements are (semantically) valid.

10. Security Considerations

Second paragraph of Section 2 (not suitable for inter-domain use
or the Internet at large) should be repeated or referred to here.

This section should be written with IMS as an example only.  The
sentence starting "In an IMS ..." and the sentence immediately
following it need some minor editing to achieve this.

Nits:
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idnits 2.04.07 complains that there is no expiration date (first
and last page) or intended status (first page).