Sending Multiple RTP Streams in a Single RTP Session: Grouping RTP Control Protocol (RTCP) Reception Statistics and Other Feedback
draft-ietf-avtcore-rtp-multi-stream-optimisation-12

[Ballot comment]
Thanks for helping me with my previous Discuss. I'm clearing, based on your proposed new text (modulo any changes that pop out of our continuing e-mail conversation).

[Ballot discuss]
I'm lost on something here, so I'd like to discuss it briefly so that I understand what I'm looking at. I'm not expecting this to be hard to resolve.

In this text

  However, the three
  SSRCs comprising each participant will almost certainly see identical
  reception quality, since they are co-located.
 
it sounds like you're describing a heuristic ("will almost certainly see", so if you use a reporting group, the results will be close enough).

In other places in the document, like

  Since they are co-located, every
  SSRC in the RTCP reporting group will have an identical view of the
  network conditions, and see the same lost packets, jitter, etc. 
 
it sounds like you're saying they'll always have an identical view ("will see", with no qualification).

Which is it?

As a comment, but on exactly the second text so I'll include it here, is "see the same lost packets" telling me that more than one SSRC is sending "the same lost packets"? If this was "see (roughly) the same loss rate", I wouldn't be surprised, but I'm confused here.

[Ballot comment]
This text

  An RTP endpoint will have one or more synchronisation sources (SSRCs)
  that send media streams.  It will have at least one SSRC for each
  media stream it sends, and might use multiple SSRCs when using media
  scalability features [RFC6190], forward error correction, RTP
  retransmission [RFC4588], or similar mechanisms.  An endpoint that is
  not sending any media streams, will have at least one SSRC to use for
  reporting and any feedback messages. 

was somewhat confusing for me. It's saying that an RTP endpoint will always have one or more SSRCs that send media streams, except that it might not send media streams, but then it still has at least one SSRC that doesn't send a media stream. Could you think about whether this could be clearer?

(Via drafts-lastcall-comment@iana.org): IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-avtcore-rtp-multi-stream-optimisation-08.txt. If any part of this review is inaccurate, please let us know.

IANA understands that, upon approval of this document, there are three actions which IANA needs to complete.

As this document requests registrations in an Expert Review or Specification Required (see RFC 5226) registry, we will initiate the required Expert Review via a separate request. Expert review will need to be completed before your document can be approved for publication as an RFC.

First, in the RTP SDES item types subregistry of the Real-Time Transport Protocol (RTP) Parameters registry located at:

https://www.iana.org/assignments/rtp-parameters/

a new item type will be added as follows:

Value: [ TBD-at-Registration ]
Abbrev: RGRP
Name: Reporting Group Identifier
Reference: [ RFC-to-be ]

Second, in the RTCP Control Packet types (PT) subregistry of the Real-Time Transport Protocol (RTP) Parameters registry also located at:

https://www.iana.org/assignments/rtp-parameters/

a new packet type is to be added to the primary assignments range as follows:

Type: [ TBD-at-Registration ]
Abbrev: RGRS
Name: Reporting Group Reporting Sources
Reference: [ RFC-to-be ]

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

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

a new attribute is to be registered as follows:

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

IANA understands that these three actions are the only ones 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. 


Thank you,

Sabrina Tanamal
IANA Specialist
ICANN

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: avtcore-chairs@ietf.org, ben@nostrum.com, roni.even@mail01.huawei.com, avt@ietf.org, draft-ietf-avtcore-rtp-multi-stream-optimisation@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Sending Multiple Media Streams in a Single RTP Session: Grouping RTCP Reception Statistics and Other Feedback) to Proposed Standard


The IESG has received a request from the Audio/Video Transport Core
Maintenance WG (avtcore) to consider the following document:
- 'Sending Multiple Media Streams in a Single RTP Session: Grouping RTCP
  Reception Statistics and Other Feedback'
  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 2015-11-24. 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


  RTP allows multiple media streams to be sent in a single session, but
  requires each Synchronisation Source (SSRC) to send RTCP reception
  quality reports for every other SSRC visible in the session.  This
  causes the number of RTCP reception reports to grow with the number
  of SSRCs, rather than the number of endpoints.  In many cases most of
  these RTCP reception reports are unnecessary, since all SSRCs of an
  endpoint are co-located and see the same reception quality.  This
  memo defines a Reporting Group extension to RTCP to reduce the
  reporting overhead in such scenarios.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-avtcore-rtp-multi-stream-optimisation/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-avtcore-rtp-multi-stream-optimisation/ballot/


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

Here is my AD Evaluation of draft-ietf-avtcore-rtp-multi-stream-optimisation-08:

Substantive Comments:
=====================

-3.1, 4th paragraph:

Is “SHOULD NOT…unless” the actual intent? That means you shouldn’t do it unless that condition occurs, or you have some other good reason and understand the consequences. (as compared to "MUST NOT … unless")

-4.2, 1st paragraph:

Does this refer to third-party observers? (That is, observers not involved in the signaling of support for rtcp-rgrp?

-7.2, reference to RFC3264:

Should this be a normative reference? I’m not sure 3.6 will make much sense without it.

Editorial Comments:
===================

-3.1, 5th paragraph:

Option "A" is hard to parse. I suggest:

"... if another reporting source exists,  have it report on the remote SSRCs that the departing source reported ..."

- 3.2.1, 2nd paragraph:

Consider active voice for the first sentence, i.e. "This document defines..."

- 3.2.2, 1st paragraph:

Consider active voice for the first sentence, i.e. "This document defines..."

- 3.6, 2nd to last paragraph: "... neither agents SHALL use..."

Please restate as SHALL NOT/MUST NOT.

-4.1, last paragraph: "approximately 8.9"

That's a rather precise approximation :-)

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. This memo defines a Reporting Group extension to RTCP to reduce the reporting overhead. The type is indicated in the title page


(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:
RTP allows multiple media streams to be sent in a single session, but requires each Synchronization Source (SSRC) to send RTCP reception  quality reports for every other SSRC visible in the session.  This causes the number of RTCP reception reports to grow with the number of SSRCs, rather than the number of endpoints.  In many cases most of these RTCP reception reports are unnecessary, since all SSRCs of an endpoint are co-located and see the same reception quality.  This memo defines a Reporting Group extension to RTCP to reduce the reporting overhead in such scenarios.


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?
The document was discussed in the meetings and on the mailing list. The open issues were addressed and there are no open issues, there was consensus on the content of the document.

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 work was done based on input from RTCWEB WG and vendors will support it.
Personnel:
Who is the Document Shepherd? Who is the Responsible Area Director?
Roni Even is the Document Shepherd.
The responsible AD is Ben Campbell.
(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 found 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 had good reviews during its progress and had good enough reviews during the WGLC.

(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. The authors confirmed.

(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
(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.
There is a new SDP attribute in the document but it is a simple one and the BNF is there.
(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 none
(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 correct and in line with the document
(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.
No IANA new registries
(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 is one formal definition of an SDP attribute. It is a very simple one with no parameters so no need for review.