Shepherd 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?

draft-ietf-perc-double is targeted at the Standards track, 
and this write­up is for Proposed Standard. This is reflected on the title page 
and in the data tracker.

(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 document define SRTP procedures for enabling end to end media 
confidentiality and integrity for end-points in a Multimedia conferences.
It does so by defining 2 types of SRTP transforms - outer and inner. 
The inner transform is responsible for ensuring end-to-end integrity 
and encryption. The outer transform covers integrity and encryption 
hop-by-hop (between endpoints and the media distributor or between 
the media distributors).

Working Group Summary

This document has been discussed and reviewed several times by the
WG. There were few individuals with concerns regarding the 
following areas
1. Allow Media distributor (MD) to modify the SSRC field 
in the RTP header. However they weren't able to propose
solutions that can mitigate the SSRC splicing attack 
identified by the WG. Also to note, the WG had previously
reached consensus on non-modifiability of the SSRC by the 
media distributor. However, the discussion was re-opened to 
help the concerned individual to put forward the proposals.
But as aforementioned, there was no proposal submitted that
satisfactorily addressed the splicing attack. Hence the 
WG decided to go forward with previously reached consensus to 
not allow MD to modify the SSRC.

2. Mechanisms to carry the end to end scoped payload header information:
Originally the proposal was to carry such information as an 
RTP header extension. However, there was a proposal to 
carry similar information as the payload header. The authors of the 
document made accommodations to work out a solution that addressed 
the concern. This involved moving the OHB from header extension to 
payload header as part of the endpoint procedures.

The chairs called for consensus - in-room and on-list -, there was
support to go with the procedures defined in the current version 
of the specification. Even though there are few individuals who aren't
totally happy, the WG had consensus on the proposals.

Also there were discussions on solution approaches for dealing 
with the repair packets. Two possible solutions were discussed. One was 
related to applying the hop-by-hop transform for the repair packet on 
the single encrypted packet vs double encrypted packet. The former 
implying a split in SRTP transform context states (E2E, RTX, HBH) and 
the latter implying a simple canonical way of doing classic SRTP 
(But just with a new transform called double). Hence the latter approach 
was chosen given its simplicity of implementing on plethora of end-points 
versus acceptable extra processing needed on relatively lower number of MD implementations.

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?

libsrtp, a widely used SRTP library in commercial and open source 
SIP  and Webrtc products, has a branch with the implementation 
for double encryption procedures as defined in this specification. 
This document did not require expert review of the types noted.


  Who is the Document Shepherd? Who is the Responsible Area

The document shepherd is Suhas Nandakumar; the responsible Area Director 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.

This document has been reviewed and discussed several times with in 
the WG. Issues and concerns brought out were significantly discussed
across several working group meetings (in-person and as part of virtual interims and design meetings.)

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

I do not have any concerns about the working group reviews to date. 

(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.

Security review is welcomed since this document defined SRTP 

(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.

As noted above, there were few individuals with concerns, but the 
chairs were able to reach consensus in support of the specification.
ADs are made aware of this situation and were closely involved 
throughout the process.

(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.


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

No IPR has been filed on this document

(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 working group as a whole concurs with this approach. 

(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.) 

There were few instances of appeal as mentioned earlier. Responsible
ADs are already made aware of this situation.

(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be

No nits were found when verified on the version 

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

This document does not present the need for these reviews.

(13) Have all references within this document been identified 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?

Not applicable.

(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 requests for downward 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 does not change the status of any existing RFC.

(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).

This document requests an update to an existing registry 
(SRTP Protection Profile); The update is not controversial within 
the working group.  

(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.

This document does not request 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.

ABNF content in the document was validated with