As required by RFC 4858, this is the current template for the Document
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?
Proposed Standard, which is appropriate since the document obsoletes RFC 4572. The title page shows the proper status.
(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:
The document specifies how to establish secure connection-oriented media transport sessions over the Transport Layer Security (TLS) protocol using the Session Description Protocol (SDP). It defines a new SDP protocol identifier, 'TCP/TLS'. It also defines the syntax and semantics for an SDP 'fingerprint' attribute that identifies the certificate that will be presented for the TLS session. This mechanism allows media transport over TLS connections to be established securely, so long as the integrity of session descriptions is assured.
This document obsoletes RFC 4572 but remains backwards compatible with older implementations. The changes from RFC 4572 are that it clarifies that multiple 'fingerprint' attributes can be used to carry fingerprints, calculated using different hash functions, associated with a given certificate, and to carry fingerprints associated with multiple certificates. The fingerprint matching procedure, when multiple fingerprints are provided, are also clarified. The document also updates the preferred cipher suite with a stronger cipher suite, and removes the requirement to use the same hash function for calculating a certificate fingerprint and certificate signature.
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
The document was adopted as a WG document in April 2016 and hence has progressed fairly quickly. WG adoption was based on strong consensus and a clear need; the document has subsequently seen good WG discussion. The document started out as an update to RFC 4572, but was more recently changed to obsolete RFC 4572 after some concerns were raised. The resulting document has solid consensus in the WG.
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?
There are various implementations of the existing RFC 4572. The new specification is needed for RTCWeb and hence several vendors are expected to implement it.
There were many individuals providing valuable input, however Martin Thomson and Roman Shpount in particular deserve special mention.
Who is the Document Shepherd? Who is the Responsible Area
Flemming Andreasen is the Document Shepherd and Ben Campbell is the Responsible AD.
(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
I have reviewed the current and several earlier versions of the document, including Nits checks.
Note that the first line on Page 3 contains two typos that should be corrected during the publication process (change "TLS to "The TLS" and "channel t" to "channel that")
(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?
No concerns. The changes to RFC 4572 are the result of extensive discussion in the WG.
(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
(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
No such 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.
(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
No 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 has received substantial discussion from several people and the WG consensus is solid at this point.
(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.)
(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
The document normatively references a NIST specification (FIPS 180-2) and an ITU-T Recommendation (X.509) which causes two "possible down-ref" comments. Both of these references are needed and were also present in the original RFC 4572.
The IP examples use IPv4 only, which seems reasonable since the document does not contain any IP version specific mechanisms or considerations.
(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type 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?
(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 two downward references (as noted above):
 National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-2, August 2002,
 International Telecommunications Union, "Information
technology - Open Systems Interconnection - The Directory:
Public-key and attribute certificate frameworks",
ITU-T Recommendation X.509, ISO Standard 9594-8, March
(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.
The document obsoletes RFC 4572, as indicated on the title page and explained in both the Abstract and Introduction.
(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).
(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.
(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 ABNF has been verified with Bill Fenner's ABNF parser.