RTP Clock Source Signalling
draft-ietf-avtcore-clksrc-11

[Ballot comment]

- s7: Your 2119 SHOULD statements seem a bit bogus as they
don't really translate into what a coder can do but I'm ok
with that.

- s7: Would it be worthwhile saying that even if you do
connect to a time source, you shouldn't use that to adjust
your system clock (as opposed to using it to sync some RTP
stuff), and if you did, then someone having a video call
with you could e.g.  cause you to accept a revoked public
key certificate and other potential badness? I suppose many
devices these days don't allow system clock changes without
user interaction, but some e.g. TVs perhaps might not get
that right if running on some home-grown operating system.

[Ballot comment]
For a readable doc about NTP AND SDP ... you win the Internet for the day.

I did have a couple of comments. Please consider them along with any other feedback you receive.

It might or might not belong in an IETF spec, but if there was a pointer to how

4.3.  Identifying PTP Reference Clocks

  Each IEEE 1588 clock is identified by a globally unique EUI-64 called
  a "ClockIdentity". 

"globally unique" is ensured, I would have been less curious ...

In 7.  Security Considerations

  Entities receiving and acting upon an SDP message SHOULD be aware
  that a session description cannot be trusted unless it has been
  obtained by an authenticated transport protocol from a known and
  trusted source. 

I'm thinking that's not an RFC 2119 SHOULD.

IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-avtcore-clksrc-09.  Authors should review the comments and/or questions below.  Please report any inaccuracies and respond to any questions as soon as possible.

We received the following comments/questions from the IANA's reviewer:

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

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

http://www.iana.org/assignments/sdp-parameters/

two new SDP names are to be registered as follows:

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

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

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

http://www.iana.org/assignments/sdp-parameters/

two new SDP names are to be registered as follows:

Type: att-field (source level)
SDP Name: ts-refclk
Reference: [ RFC-to-be ]

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

Third, a new subregistry of the Session Description Protocol (SDP) Parameters registry located at:

http://www.iana.org/assignments/sdp-parameters/

called the Timestamp Reference Clock Source Parameters Registry.  This new subregistry will be maintained via Specification Required as defined in RFC 5226.

There are three fields for each registration in the subregistry.

Name:  Token used in the SDP description (clksrc-param-name)
Long name:  Descriptive name for the timestamp reference clock source
Reference:  Reference to the document describing the SDP token (clksrc-param-name) and syntax for the optional value associated with the token (mediaclock-param-value)

There are initial registrations in this new subregistry as follows:

+---------+-------------------------+--------------------------+
| Name    | Long Name              | Reference                |
+---------+-------------------------+--------------------------+
| ntp    | Network Time Protocol  | [ RFC-to-be ]            |
| ptp    | Precision Time Protocol | [ RFC-to-be ]            |
| gps    | Global Position System  | [ RFC-to-be ]            |
| gal    | Galileo                | [ RFC-to-be ]            |
| local  | Local Clock            | [ RFC-to-be ]            |
| private | Private Clock          | [ RFC-to-be ]            |
+---------+-------------------------+--------------------------+

Fourth, a new subregistry of the Session Description Protocol (SDP) Parameters registry located at:

http://www.iana.org/assignments/sdp-parameters/

called the Media Clock Source Parameters Registry.  This new subregistry will be maintained via Specification Required as defined in RFC 5226.

There are three fields for each registration in the subregistry.

Name:  Token used in the SDP description (mediaclock-param-name)
Long name:  Descriptive name for the media clock source type
Reference:  Reference to the document describing the SDP token (mediaclock-param-name) and syntax for the optional value associated with the token (mediaclock-param-value)

There are initial registrations in this new subregistry as follows:

+-------------+---------------------------------+-------------------+
| Name        | Long Name                      | Reference        |
+-------------+---------------------------------+-------------------+
| sender      | Asynchronously Generated Media  | [ RFC-to-be ]    |
|            | Clock                          |                  |
| direct      | Direct-Referenced Media Clock  | [ RFC-to-be ]    |
|            |                                |                  |
| IEEE1722    | IEEE1722 Media Stream          | [ RFC-to-be ]    |
|            | Identifier                      |                  |
+-------------+---------------------------------+-------------------+

IANA understands that these are the only actions required to be completed 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.
This message is only to confirm what actions will be performed.

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (RTP Clock Source Signalling) to Proposed Standard


The IESG has received a request from the Audio/Video Transport Core
Maintenance WG (avtcore) to consider the following document:
- 'RTP Clock Source Signalling'
  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 2014-01-16. 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


  NTP format timestamps are used by several RTP protocols for
  synchronisation and statistical measurements.  This memo specifies
  SDP signalling identifying timestamp reference clock sources and SDP
  signalling identifying the media clock sources in a multimedia
  session.





The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-avtcore-clksrc/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-avtcore-clksrc/ballot/


No IPR declarations have been submitted directly on this I-D.

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?
This document will be a standard track RFC, it specifies SDP signaling for reference and media clock sources. The type is indicated in the title page header.

(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

  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.



  NTP format timestamps are used by several RTP protocols for synchronisation and statistical measurements.  This memo specifies SDP signalling identifying timestamp reference clock sources and SDP signalling identifying the media clock sources in a multimedia session.

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?
This document was written as a result of discussion on another draft which made it clear that there is a need to be able to specify the clock used for RTP in order to achieve better synchronization between sources. It was seen as a general problem and this document represent the WG consensus.

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 authors are aware of two implementation that use at least some of the signaling capabilities described in this draft: http://soundandpicture.com/2013/11/axia-announces-first-broadcast-product-with-aes67-compliance/ and http://ravenna.alcnetworx.com/technology/open-technology-standards/aes67-x192.html
The draft is a normative reference for the recently published AES67 standard and the is referenced by https://ietf.org/doc/draft-ietf-avtcore-idms/ which is now in the RFC editor queue waiting for this document.
There was an SDP directorate review and comments were addressed.


Personnel

  Who is the Document Shepherd? Who is the Responsible Area
  Director?
Document Shepherd is Roni Even and the responsible AD is Richard Barnes.

(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 reviewed the document in previous and current version and find it ready for publication.


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

The document got good reviews in the WG and there are no concerns.

(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.
No need

(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.

No 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.

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

No IPR disclosures.

(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 WG understand the document and agree 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
(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.
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 need, had SDP directorate review.
(13) Have all references within this document been identified as
either normative or informative?
Yes
(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?
No.

(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 normative references to IEEE documents.

(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.
No

(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 IANA section is in line with the document and all new registries have the initial content and procedures for future allocations.

(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.
There are no expert review required registries. All new ones have specification required policy

(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.
There was an SDP directorate review on the SDP section. Comments were addressed and approved by Paul Kyzivat who did the review.