RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count Metric Reporting
draft-ietf-xrblock-rtcp-xr-discard-15

[Ballot comment]

Sam Hartman's secdir review [1] of xr-discard-rle-metrics
raised a good question that's probably better asked here,
or here as well. I'm not asking for any change in this or
any specific xrblock document, but I would ask that the
WG do consider this. Sam said:

"Has the WG analyzed implications of providing feedback
to an attacker on what specific SRTP packets are
discarded?  In the past we've run into trouble with
security systems that were too verbose in error
reporting.  As an example, in certain public-key crypto
constructions knowing whether a packet produced a
decoding error vs a signature error after decryption can
provide an attacker generating forged packets valuable
information to attack the system.

It's quite possible that SRTP doesn't have problems in
this regard.  I just want to confirm that the analysis
has been done."

I think that's a good question because knowing at what
stage in a security protocol a message was barfed or
getting timing statistics can expose information about
how some crypto operation went wrong, and that can be
exploited via statistical techniques with a sufficiently
large number of messages.  See for example the lucky-13
attacks against certain cryptographic modes in TLS [2] or
perhaps the "original" of the species, the Bleichenbacher
attack.  [3]

I suspect the best thing to do might be for the wg to try
grab a security person and ponder this for a bit, if
that's not already been done. I'm happy to try help find
a co-ponderer if you want:-) Maybe we can ambush one in a
hallway in Berlin.

  [1] http://www.ietf.org/mail-archive/web/secdir/current/msg04048.html
  [2] http://www.isg.rhul.ac.uk/tls/Lucky13.html
  [3] https://en.wikipedia.org/wiki/Adaptive_chosen-ciphertext_attack

[Ballot comment]
-
  Block type (BT): 8 bits

      A Discard Count Metric Report Block is identified by the constant
      PDC.

      [Note to RFC Editor: please replace PDC with the IANA provided
      RTCP XR block type for this block.]

Figure 1 needs to be changed as well, not only the text.

-
Section 1.4

  This metric is believed to be applicable to a large class of RTP
  applications which use a jitter buffer.

Isn't a de-jitter buffer? See https://tools.ietf.org/html/rfc5481#section-3.2

[Ballot comment]
My apologies for updating this comment after looking at similar text in the -jt draft. You can ignore my previous comment on -discard.

In this text, 4.  SDP Signaling

  [RFC3611] defines the use of SDP (Session Description Protocol)
  [RFC4566] for signaling the use of XR blocks.  However XR blocks MAY
  be used without prior signaling (see section 5 of RFC3611).


This text is saying, to me:

- You can signal the use of XR blocks in SDP,

- or not

- but if you do signal the use of XR blocks in SDP, here's how you would do that for discards

Is there any guidance you can give about which choice an implementer should lean toward?

[Ballot comment]
In this text, 4.  SDP Signaling

  [RFC3611] defines the use of SDP (Session Description Protocol)
  [RFC4566] for signaling the use of XR blocks.  However XR blocks MAY
  be used without prior signaling (see section 5 of RFC3611).

Could you consider adding a sentence saying something like "the rest of section 4 is extending SDP to allow signaling the use of discard blocks"? That would have been helpful to me.

IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-xrblock-rtcp-xr-discard-14.  Authors should review the comments and/or questions below.  Please report any inaccuracies and respond to any questions as soon as possible.

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

First, in the RTCP XR Block Type registry in the RTP Control Protocol Extended Reports (RTCP XR) Block Type page located at

http://www.iana.org/assignments/rtcp-xr-block-types

a new Block Type will be registered as follows:

BT: [ TBD-at-registration ]
Name: Discard Count Metrics Block
Reference: [ RFC-to-be ]

Second, in the RTCP XR SDP Parameters registry in the RTP Control Protocol Extended Reports (RTCP XR) Session Description Protocol (SDP) Parameters page located at

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

a new SDP Parameter will be registered as follows:

Parameter: pkt-discard-count
Reference: [ RFC-to-be ]

IANA understands that these are the only actions 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. 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 Control Protocol (RTCP) Extended Report (XR) Block for Discard Count metric Reporting) to Proposed Standard


The IESG has received a request from the Metric Blocks for use with
RTCP's Extended Report Framework WG (xrblock) to consider the following
document:
- 'RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard
  Count metric Reporting'
  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 2013-06-03. 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


  This document defines an RTP Control Protocol(RTCP) Extended Report
  (XR) Block that allows the reporting of a simple discard count metric
  for use in a range of RTP applications.




The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-xrblock-rtcp-xr-discard/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-xrblock-rtcp-xr-discard/ballot/


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

(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?

The document is being requested as a Standards Track RFC.

The document defines one new Extended Report (XR)
Report Block [RFC 3611] and standards track is appropriate for this document.

Standards Track 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

This draft defines a new block type to augment those defined in
[RFC3611] for use in a range of RTP applications. The new block type
supports the reporting of the per-packet report metric capturing individual
packets discarded from the jitter buffer after successful reception.


Working Group Summary

There were several points of debate within the working group; however,
none were particularly rough and authors and commentators came up
with the text that resolves any issues thus consensus was achieved in
all cases.

There was a long debate on discard type for "both" (discard type indicating
a combination of different discard type). After long debate the WG
concluded to remove this ambiguous discard type and clarified how
one should report when there are multiple reasons why report packet
was discarded.

Document Quality

This document has been reviewed by numerous people within
XRBLOCK and through two rounds of WGLCs the document
resolved any outstanding issues.

The document has been reviewed by SDP directorate post WGLC
for SDP extensions defined, some issues surrounding clarity of
how the extension is used was raised but was resolved.

The document has been submitted to performance metric
directorate for a review prior to this draft being submitted for
IESG review.

Personnel

Shida Schubert 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.

I have reviewed the last two iterations of this document, including providing
technical and editorial review comments during the WGLC reviews.
All of my comments and that of others provided during WGLC are addressed.

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

No.

(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.

(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.

There are 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.

(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?

Yes, there is strong consensus.

(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 concern..

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

No formal reviews are required for this document.
The review by PM-DIR has been requested and authors have added
the RFC6390 template with the assumption that it will be requested
by PM-DIR.

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

No.

(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).

Appropriate reservations have been included for IANA registries.

(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.

(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.

None required.
BNF was reviewed by the SDP directorate.