Session Description Protocol (SDP) Media Capabilities Negotiation
draft-ietf-mmusic-sdp-media-capabilities-17

[Ballot comment]
Thank you for including the specific ways in which
this document updates RFC 5939:

  This document updates RFC 5939 [RFC5939] by updating the IANA
  Considerations.  All other extensions defined in this document are
  considered extensions above and beyond RFC 5939 [RFC5939].

[Ballot comment]
One minor question added to my original comments: The writeup does not indicate any implementation of this. Is that true? There are no implementations yet?

This stuff is well outside of my area of expertise. After a read through, I have found nothing *in* my area of expertise that is problematic. A couple of requirements language issues, but nothing that should stop the document unless other ADs think these problems could cause serious problems:

3.4.1.1:

The following happens elsewhere in the document, but this is a good example:

  Each potential configuration
  MUST include a config-number that is unique in the entire SDP...

That's ambiguous. What "MUST" be done here? Do you mean:

  Each potential configuration MUST include a config-number, which is
  unique in the entire SDP.

Or do you mean:

  The config-number of each potential configuration MUST be
  unique in the entire SDP.
 
Or do you mean:

  Each potential configuration MUST include a config-number, and
  each config-number MUST be unique in the entire SDP.
 
Which is it? They have 3 different meanings. The first is saying to the implementer, "You might not think the config number is required, but it is and you'll screw up the other side if you leave it out." The second is saying, "You might not think the config number needs to be unique, but it does and you'll screw up the other side if it's not." And the third is saying the combination of the first two.

It is probably worth reviewing 2119 usage throughout the document, as ambiguities in requirements is a bad thing. And even though this is ambiguous, the RFC Editor will likely not try to correct it because they always assume that things around requirements language were worded carefully. Please check them.

3.4.2.1:

  The answerer MUST first determine...

I very much doubt that this is an interoperability requirement. There are several instances of this sort. Please remove these MUSTs.

[Ballot comment]
This stuff is well outside of my area of expertise. After a read through, I have found nothing *in* my area of expertise that is problematic. A couple of requirements language issues, but nothing that should stop the document unless other ADs think these problems could cause serious problems:

3.4.1.1:

The following happens elsewhere in the document, but this is a good example:

  Each potential configuration
  MUST include a config-number that is unique in the entire SDP...

That's ambiguous. What "MUST" be done here? Do you mean:

  Each potential configuration MUST include a config-number, which is
  unique in the entire SDP.

Or do you mean:

  The config-number of each potential configuration MUST be
  unique in the entire SDP.
 
Or do you mean:

  Each potential configuration MUST include a config-number, and
  each config-number MUST be unique in the entire SDP.
 
Which is it? They have 3 different meanings. The first is saying to the implementer, "You might not think the config number is required, but it is and you'll screw up the other side if you leave it out." The second is saying, "You might not think the config number needs to be unique, but it does and you'll screw up the other side if it's not." And the third is saying the combination of the first two.

It is probably worth reviewing 2119 usage throughout the document, as ambiguities in requirements is a bad thing. And even though this is ambiguous, the RFC Editor will likely not try to correct it because they always assume that things around requirements language were worded carefully. Please check them.

3.4.2.1:

  The answerer MUST first determine...

I very much doubt that this is an interoperability requirement. There are several instances of this sort. Please remove these MUSTs.

[Ballot comment]

- 3.3.5: Does the crypto field only ever contain symmetric key
material or initialisation values? If so, why only have a
SHOULD NOT for use of real key materials in a latent (or
potential?) configuration? I don't see why that is not a MUST
NOT. Actually, having a MUST for some known value would
maybe be even better, e.g. all zeros, so long as that didn't
break anything.  (Same thing if crypto can occur in an answer
as a latent value.)

[Ballot comment]
Nits:

Do you want to explicitly say whether a range of 3-1 is semantically legal? It is syntactically valid, and the text doesn't require the number represented by the digits to the right of the hyphen to be greater than that to the left.

This (and several documents that have gone before it) use 1*10(DIGIT) for things like media-cap-num. That means
it would be syntactically valid to say things like

a=rmcap:1 PCMU/8000
and
a=rmcap:00001 PCMU/8000

Do those mean the same thing?

If someone included a pcfg with m=0001|0002 in an offer, and the answer had a acfg with m=1, should the offerer recognize that as the same as its 0001?

Would it be better to restrict the syntax to avoid this question?

IANA has reviewed draft-ietf-mmusic-sdp-media-capabilities-15 and has the following comments:

IANA understands that, upon approval of this document, there are five actions which IANA must complete.

First, in the SDP Attrribute subregistry - att-field (both session and media
level) - in the Session Description Protocol (SDP) Parameters registry located at:

www.iana.org/assignments/sdp-parameters/sdp-parameters.xml

the following four SDP attributes will be registered as follows:

Type: att-field (both session and media level)
SDP Name: rmcap
Reference: [ RFC-to-be ]

Type: att-field (both session and media level)
SDP Name: omcap
Reference: [ RFC-to-be ]

Type: att-field (both session and media level)
SDP Name: mfcap
Reference: [ RFC-to-be ]

Type: att-field (both session and media level)
SDP Name: mscap
Reference: [ RFC-to-be ]

Second, in the SDP Attribute subregistry - att-field (media level only) - in
the Session Description Protocol (SDP) Parameters registry located at:

www.iana.org/assignments/sdp-parameters/sdp-parameters.xml

the following SDP attribute will be registered as follows:

Type: att-field (media level only)
SDP Name: lcfg
Reference: [ RFC-to-be ]

Third, in the SDP Attribute subregistry - att-field (session level) - in the
Session Description Protocol (SDP) Parameters registry located at:

www.iana.org/assignments/sdp-parameters/sdp-parameters.xml

the following SDP attribute will be registered as follows:

Type: att-field (session level)
SDP Name: sescap
Reference: [ RFC-to-be ]

Fourth, in the SDP Capability Negotiation Option Tags subregistry in the Session
Description Protocol (SDP) Parameters registry located at:

www.iana.org/assignments/sdp-parameters/sdp-parameters.xml

the following SDP Capability Negotiation Option Tag will be registered as follows:

Option Tag: med-v0
Reference: [ RFC-to-be ]

Fifth, a series of changes are to be made to the SDP Capability Negotiation
Potential Configuration Parameters subregistry in the Session Description
Protocol (SDP) Parameters registry located at:

www.iana.org/assignments/sdp-parameters/sdp-parameters.xml

The name of the registry should be "SDP Capability Negotiation Configuration
Parameters Registry"

The registry will be changed to have the following information for each
registration:

Encoding Name: The syntactical value used for the capability negotiation
configuration parameter, as defined in [RFC5939], Section 3.5.

Descriptive Name: The name commonly used to refer to the capability negotiation
configuration parameter.

Potential Configuration Definition: A reference to the RFC that defines the
configuration parameter in the context of a potential configuration attribute.
If the configuration parameter is not defined for potential configurations, the
string "N/A" (Not Applicable) MUST be present instead.

Actual Configuration Definition: A reference to the RFC that defines the
configuration parameter in the context of an actual configuration attribute. If
the configuration parameter is not defined for actual configurations, the string
"N/A" (Not Applicable) MUST be present instead.

Latent Configuration Definition: A reference to the RFC that defines the
configuration parameter in the context of a latent configuration attribute. If
the configuration parameter is not defined for latent configurations, the string
"N/A" (Not Applicable) MUST be present instead.

The registration policy is changed to RFC Required as defined in RFC 5226.

The existing registrations will be changed as follows:

Encoding Name: a
Descriptive Name: Attribute Configuration
Potential Configuration Definition: [RFC5939]
Actual Configuration Definition: [RFC5939]
Latent Configuration Definition: [ RFC-to-be ]

Encoding Name: t
Descriptive Name: Transport Protocol Configuration
Potential Configuration Definition: [RFC5939]
Actual Configuration Definition: [RFC5939]
Latent Configuration Definition: [ RFC-to-be ]

In addition, three new registrations will be made in the newly modified registry:

Encoding Name: m
Descriptive Name: Media Configuration
Potential Configuration Definition: [ RFC-to-be ]
Actual Configuration Definition: [ RFC-to-be ]
Latent Configuration Definition: [ RFC-to-be ]

Encoding Name: pt
Descriptive Name: Payload Type Number Mapping
Potential Configuration Definition: [ RFC-to-be ]
Actual Configuration Definition: [ RFC-to-be ]
Latent Configuration Definition: [ RFC-to-be ]

Encoding Name: mt
Descriptive Name: Media Type
Potential Configuration Definition: N/A
Actual Configuration Definition: N/A
Latent Configuration Definition: [ RFC-to-be ]

IANA understands that these five actions are the only ones required upon
approval of this document.

Note: The actions requested in this document will not be completed
until the document has been approved for publication as an RFC.

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Subject: Last Call:  (Session Description Protocol (SDP) Media Capabilities Negotiation) to Proposed Standard


The IESG has received a request from the Multiparty Multimedia Session
Control WG (mmusic) to consider the following document:
- 'Session Description Protocol (SDP) Media Capabilities Negotiation'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2012-11-12. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract


  Session Description Protocol (SDP) capability negotiation provides a
  general framework for indicating and negotiating capabilities in SDP.
  The base framework defines only capabilities for negotiating
  transport protocols and attributes.  In this document, we extend the
  framework by defining media capabilities that can be used to
  negotiate media types and their associated parameters.

  This document updates the IANA Considerations of RFC 5939.




The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-mmusic-sdp-media-capabilities/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-mmusic-sdp-media-capabilities/ballot/


The following IPR Declarations may be related to this I-D:

  http://datatracker.ietf.org/ipr/829/

Document Writeup

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)? Why
is this the proper type of RFC? Is this type of RFC indicated in the
title page header?

Standards Track

(2) 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

The Session Description Protocol (SDP) has a general framework for
endpoints to indicate and negotiate capabilities within SDP. However,
the base framework defines capabilities for negotiating transport
protocols and attributes. In this document, the SDP capability
negotiation framework is extended with the ability to additionally
indicate and negotiate media types and their associated parameters.


Working Group Summary

The first version of the document is dating February 2007. Since
then, the MMUSIC working group has been progressing the document
until getting satisfied with the current version.


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?

The document has been reviewed and contributed by many participants
of the working group, among others: Culleng Jennings, Christer
Holmberg, Matt Lepinski, Joerg Ott, Colin Perkins, Thomas Stach,
Ingemar Johansson, Andrew Allen, and Magnus Westerlund.

The document was first WGLCed on version 10 (July 2010) and subsequently
on version 14 (July 2012). All the open issues have been addressed
and the WG has got consensus on version 15.

Personnel

Miguel Garcia is the Document Shepherd. Gonzalo Camarillo is the
Responsible Area Director.


(3) Briefly describe the review of this document that was performed by
the Document Shepherd. If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.

The Document Shepherd has reviewed version 13 and the requested (minor) changes introduced in versions 14 and 15.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?

No concerns. The document has been widely reviewed throughout the time.

(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.

There is no need for this type of reviews.

(6) Describe any specific concerns or issues that the Document Shepherd
has 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.

The Document Shepherd is satisfied with the document. There are no
extra concerns.

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.

Yes, authors have confirmed that all appropriate IPR disclosure has
been filed.

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.

There is one IPR disclosure #829 submitted. The mailing list was
informed on April 4th, 2007. There has not been any e-mail discussion
regarding this IPR disclosure.

(9) 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?

The document represents a solid consensus from the WG. It is believed
that the WG as a whole understand and agrees with it.

(10) 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 publicly available.)

No, no such threat exists.

(11) Identify any ID nits the Document Shepherd has found in this
document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.

IDnits reports no issues.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

No such review is required in this document.

(13) Have all references within this document been identified as
either normative or informative?

Yes, all references are classified as either normative or informative.

(14) 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 plan for their completion?

There is no such dependency

(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in the
Last Call procedure.

There are no downward normative references.

(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.

This document updates RFC 5939, just because an existing registry,
initially created by RFC 5939, is modified and updated by this
document. The actual extensions defined by this document do not update
any document.

(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).

The Document Shepherd has reviewed the IANA considerations
section. The aim of the section is clear and well done.

(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.

None such registries require Expert Review.

(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

The Document Shepherd has validated the ABNF with the BAP
parser. BAP indicates a few suggestions to improve the readability of
the ABNF. The ABNF seems to be correct.