Message Body Handling in the Session Initiation Protocol (SIP)
draft-ietf-sip-body-handling-06

IANA Last Call comments:

Upon approval of this document, the IANA will make the following changes:

1. In the "mail-cont-disp" registry located at
http://www.iana.org/assignments/mail-cont-disp, in the sub-registry named "Mail
Content Disposition Values", add the following record:

Name = by-reference
Description = The body needs to be handled according to a reference to the body
that is located in the same SIP message as the body.
Reference = [RFC-sip-body-handling-06]

2. In the "sip-parameters" registry located at
http://www.iana.org/assignments/sip-parameters, in the sub-registry named
"Header Field Parameters and Parameter Values", make the following change:

OLD:
Predefined
Header Field Parameter Name Values Reference
------------------- --------------- ---------- ---------
Content-Disposition handling Yes [RFC3261]

NEW:
Predefined
Header Field Parameter Name Values Reference
------------------- --------------- ---------- ---------
Content-Disposition handling Yes [RFC3204][RFC3261][RFC3459][RFC-sip-body-handling-06]

[Ballot comment]
This is a good document.

Some minor comments:

3.1.  Background on Message Body Encoding

[...]

  SIP uses S/MIME [RFC3850] to protect message bodies.  As specified in

Here and in one other place: I think you really meant RFC 3851:

Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1
Message Specification

and not RFC 3850:

Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1
Certificate Handling

  [RFC3261], UASs that cannot decrypt a message body or a body part can
  use the 493 (Undecipherable) response to report the error.

I think explicit statement that support for multipart/signed is OPTIONAL
by UAS and UAC would benefit the document.


3.2.  UA Behavior to Encode Binary Message Bodies

  SIP messages can carry binary message bodies such as legacy
  signalling objects [RFC3204].  SIP proxy servers are 8-bit safe.
  That is, they are able to handle binary bodies.  Therefore, there is
  no need to use encodings such as base64 to transport binary bodies in
  SIP messages.  Consequently, UAs SHOULD use the binary transfer
  encoding

I think this needs a reference to [RFC4289] where the "binary" content transfer
encoding is defined.

  for all payloads in SIP, including binary payloads.  The
  only case where a UA MAY use a different encoding is when
  transferring application data between applications that only handle a
  different encoding (e.g., base64).

4.2.  Mandatory Support for 'multipart' Message Bodies

[...]

      It has been observed on the field that a number of legacy SIP UAs

I think it should be "in the field".

      without support for 'multipart' bodies simply ignored those bodies
      when they were received.  These UAs did not return any error



4.3.  UA Behavior to Generate 'multipart' Message Bodies

[...]

      Note that UAs receiving unnecessarily nested body parts treat them
      as if they were not nested.

I think this sentence is a bit ambiguous, so you should consider clarifying it.


10.  Guidelines to Authors of SIP Extensions

  These guidelines are intended for authors of SIP extensions that
  involve, in some way, message bodies or body parts.  These guidelines
  discuss aspects authors of such extensions need to consider when
  design them.

s/design/designing

[Ballot comment]
This is a good document. I am thinking about voting "Yes" on it.

Some minor comments:

3.1.  Background on Message Body Encoding

[...]

  SIP uses S/MIME [RFC3850] to protect message bodies.  As specified in

Here and in one other place: I think you really meant RFC 3851:

Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1
Message Specification

and not RFC 3850:

Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1
Certificate Handling

  [RFC3261], UASs that cannot decrypt a message body or a body part can
  use the 493 (Undecipherable) response to report the error.


3.2.  UA Behavior to Encode Binary Message Bodies

  SIP messages can carry binary message bodies such as legacy
  signalling objects [RFC3204].  SIP proxy servers are 8-bit safe.
  That is, they are able to handle binary bodies.  Therefore, there is
  no need to use encodings such as base64 to transport binary bodies in
  SIP messages.  Consequently, UAs SHOULD use the binary transfer
  encoding

I think this needs a reference to [RFC4289] where the "binary" content transfer
encoding is defined.

  for all payloads in SIP, including binary payloads.  The
  only case where a UA MAY use a different encoding is when
  transferring application data between applications that only handle a
  different encoding (e.g., base64).

4.2.  Mandatory Support for 'multipart' Message Bodies

[...]

      It has been observed on the field that a number of legacy SIP UAs

I think it should be "in the field".

      without support for 'multipart' bodies simply ignored those bodies
      when they were received.  These UAs did not return any error



4.3.  UA Behavior to Generate 'multipart' Message Bodies

[...]

      Note that UAs receiving unnecessarily nested body parts treat them
      as if they were not nested.

I think this sentence is a bit ambiguous, so you should consider clarifying it.


10.  Guidelines to Authors of SIP Extensions

  These guidelines are intended for authors of SIP extensions that
  involve, in some way, message bodies or body parts.  These guidelines
  discuss aspects authors of such extensions need to consider when
  design them.

s/design/designing

The SIP working group would like to request publication of  draft-ietf-
sip-body-handling-06. This is a product of the SIP working group and 
is intended for standards track.

Theo Zourzouvillys  will serve as the draft shepherd, 
supported by SIP working group chair Dean Willis.

A write-up, prepared by Theo, is attached. Note that there is an 
Instruction to the RFC Editor attached to correct two minor typos in 
XML and example SIP messages that prevent validation.

[This template version is dated September 17, 2008.]

(for draft-ietf-sip-body-handling-06)

    (1.a) Who is the Document Shepherd for this document? Has the
          Document Shepherd personally reviewed this version of the
          document and, in particular, does he or she believe this
          version is ready for forwarding to the IESG for publication?

The Document Shepherd for this document is Theo Zourzouvillys.  I have 
read
this version of the draft and believe it is ready for forwarding to 
the IESG
for publication.

    (1.b) Has the document had adequate review both from key WG members
          and from key non-WG members? Does the Document Shepherd have
          any concerns about the depth or breadth of the reviews that
          have been performed?

This document has had solid, in-depth reviews from working group 
members.

    (1.c) Does the Document Shepherd have concerns that the document
          needs more review from a particular or broader perspective,
          e.g., security, operational complexity, someone familiar with
          AAA, internationalization or XML?

There are no concerns.

    (1.d) Does the Document Shepherd have any specific concerns or
          issues with this document that the Responsible Area Director
          and/or the IESG should be aware of? For example, perhaps he
          or she is uncomfortable with certain parts of the document, 
or
          has concerns whether there really is a need for it. In any
          event, if the WG has discussed those issues and has indicated
          that it still wishes to advance the document, detail those
          concerns here. Has an IPR disclosure related to this document
          been filed? If so, please include a reference to the
          disclosure and summarize the WG discussion and conclusion on
          this issue.

I have no concerns with this document, and believe there is a need for 
it.

There have been no IPR disclosures for this document.

    (1.e) How solid is the WG consensus behind this document? Does it
          represent the strong concurrence of a few individuals, with
          others being silent, or does the WG as a whole understand and
          agree with it?

WG consensus appears to be solid.

    (1.f) Has anyone threatened an appeal or otherwise indicated 
extreme
          discontent? If so, please summarise the areas of conflict in
          separate email messages to the Responsible Area Director. (It
          should be in a separate email because this questionnaire is
          entered into the ID Tracker.)

No one has expressed any discontent with this document.

    (1.g) Has the Document Shepherd personally verified that the
          document satisfies all ID nits? (See
          http://www.ietf.org/ID-Checklist.html and
          http://tools.ietf.org/tools/idnits/). Boilerplate checks are
          not enough; this check needs to be thorough. Has the document
          met all formal review criteria it needs to, such as the MIB
          Doctor, media type and URI type reviews?

The document shepherd has personally verified that this version of the
document satisfies all of the ID nits, bar a warning about legal
boilerplate about pre-RFC5378 work.

    (1.h) Has the document split its references into normative and
          informative? Are there normative references to documents that
          are not ready for advancement or are otherwise in an unclear
          state? If such normative references exist, what is the
          strategy for their completion? Are there normative references
          that are downward references, as described in [RFC3967]? If
          so, list these downward references to support the Area
          Director in the Last Call procedure for them [RFC3967].

The document has been split into normative and informative references.

All normative references are stable.

    (1.i) Has the Document Shepherd verified that the document IANA
          consideration section exists and is consistent with the body
          of the document? If the document specifies protocol
          extensions, are reservations requested in appropriate IANA
          registries? Are the IANA registries clearly identified? If
          the document creates a new registry, does it define the
          proposed initial contents of the registry and an allocation
          procedure for future registrations? Does it suggest a
          reasonable name for the new registry? See [RFC5226]. If the
          document describes an Expert Review process has Shepherd
          conferred with the Responsible Area Director so that the IESG
          can appoint the needed Expert during the IESG Evaluation?

This document contains two considerations for IANA. in the IANA 
considerations
section (section 12):

  * Registration of the 'by-reference' Disposition Type in the 
existing IANA
    registry for Content-Disposition 'Handling Parameter Values', 
created
    by RFC3204 at http://www.iana.org/assignments/mail-cont-disp

  * request an update to the 'handling' parameter in the existing 
'SIP Header
    Field Parameters and Parameter Values' registry created by 
RFC3968, at
    http://www.iana.org/assignments/sip-parameters

Neither of these registries require Expert Review for additions or
modifications.


    (1.j) Has the Document Shepherd verified that sections of the
          document that are written in a formal language, such as XML
          code, BNF rules, MIB definitions, etc., validate correctly in
          an automated checker?

The XML in figure 2 does not validate due to a missing closing XML '>' 
on
the 'resource-lists' element (line 250), and the Content-Length on 
line 230
is also incorrect.  Please see [Instructions for RFC Editor] for 
instructions
to correct this issue.

SIP messages and SDP bodies in examples have been manually checked and 
appear
valid.

    (1.k) The IESG approval announcement includes a Document
          Announcement Write-Up. Please provide such a Document
          Announcement Write-Up? Recent examples can be found in the
          "Action" announcements for approved documents. The approval
          announcement contains the following sections:

          Technical Summary
              Relevant content can frequently be found in the abstract
              and/or introduction of the document. If not, this may be
              an indication that there are deficiencies in the abstract
              or introduction.


    This document specifies how message bodies should be handled in SIP.
    Additionally, this document specifies SIP user agent support for 
MIME
    (Multipurpose Internet Mail Extensions) in message bodies.


          Working Group Summary
              Was there anything in WG process that is worth noting? For
              example, was there controversy about particular points or
              were there decisions where the consensus was particularly
              rough?


There is consensus in the working group to publish this document, and is
targeted for Standards Track.  Work on this document began in May 2007,
and was adopted as a working group item in August 2007. WGLC was issued
in June 2008.


          Document Quality
              Are there existing implementations of the protocol? Have a
              significant number of vendors indicated their plan to
              implement the specification? Are there any reviewers that
              merit special mention as having done a thorough review,
              e.g., one that resulted in important changes or a
              conclusion that the document had no substantive issues? If
              there was a MIB Doctor, Media Type or other expert review,
              what was its course (briefly)? In the case of a Media Type
              review, on what date was the request posted?

This document specifically addresses an area of SIP that has been an
interoperability problem in the past.  The SIPit interoperability 
events have
seen many problems in the area of interoperability of MIME handling.

This document has been reviews by many participants over the lifetime 
of the
document, by the following members of the WG:

  - Paul Kyzivat
  - John Elwell
  - Francois Audet
  - Dan Wing
  - Eric Burger
  - Dale Worley
  - Jonathan Rosenberg
  - Cullen Jennings
  - Adam Roach

Additionally, an extensive APPS area review of the document was been 
performed
by Dave Crocker in an eary version of the this document.






[Instructions for RFC Editor]

The XML in figure 2 is invalid due to a missing '>'.  The Content-
Length in
the same message is also invalid.

Please replace line 230, which is currently:

      Content-Length: 617

with:

      Content-Length: 619



Please replace line 250, which is currently: