rfc8843v5.txt   rfc8843.txt 
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not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction 1. Introduction
1.1. Background 1.1. Background
1.2. BUNDLE Mechanism 1.2. BUNDLE Mechanism
1.3. Protocol Extensions 1.3. Protocol Extensions
1.4. Contradiction regarding bundle-only "m=" sections
2. Terminology 2. Terminology
3. Conventions 3. Conventions
4. Applicability Statement 4. Applicability Statement
5. SDP Grouping Framework BUNDLE Extension 5. SDP Grouping Framework BUNDLE Extension
6. SDP 'bundle-only' Attribute 6. SDP 'bundle-only' Attribute
7. SDP Offer/Answer Procedures 7. SDP Offer/Answer Procedures
7.1. Generic SDP Considerations 7.1. Generic SDP Considerations
7.1.1. Connection Data ("c=") 7.1.1. Connection Data ("c=")
7.1.2. Bandwidth ("b=") 7.1.2. Bandwidth ("b=")
7.1.3. Attributes ("a=") 7.1.3. Attributes ("a=")
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* defines a new RTCP [RFC3550] SDES item, 'MID', and a new RTP SDES * defines a new RTCP [RFC3550] SDES item, 'MID', and a new RTP SDES
header extension that can be used to associate RTP streams with header extension that can be used to associate RTP streams with
"m=" sections. "m=" sections.
* updates [RFC7941] by adding an exception, for the MID RTP header * updates [RFC7941] by adding an exception, for the MID RTP header
extension, to the requirement regarding protection of an SDES RTP extension, to the requirement regarding protection of an SDES RTP
header extension carrying an SDES item for the MID RTP header header extension carrying an SDES item for the MID RTP header
extension. extension.
1.4. Contradiction regarding bundle-only "m=" sections
Since the approval of the WebRTC specification documents, the IETF
has become aware of an inconsistency between the document specifying
JSEP and the document specifying BUNDLE (RFC 8829 and this RFC,
respectively). Rather than delaying publication further to come to a
resolution, the documents are being published as they were originally
approved. The IETF intends to restart work on these technologies,
and revised versions of these documents will be published as soon as
a resolution becomes available.
The specific issue involves the handling of "m=" sections that are
designated as bundle-only, as discussed in [RFC8829], Section 4.1.1.
Currently, there is divergence between JSEP and BUNDLE, as well as
between these specifications and existing browser implementations:
* JSEP prescribes that said "m=" sections should use port zero and
add an "a=bundle-only" attribute in initial offers, but not in
answers or subsequent offers.
* BUNDLE prescribes that these "m=" sections should be marked as
described in the previous point, but in all offers and answers.
* Most current browsers do not mark any "m=" sections with port zero
and instead use the same port for all bundled "m=" sections; one
follows the JSEP behavior.
2. Terminology 2. Terminology
"m=" section: SDP bodies contain one or more media descriptions, "m=" section: SDP bodies contain one or more media descriptions,
referred to as "m=" sections. Each "m=" section is represented referred to as "m=" sections. Each "m=" section is represented
by an SDP "m=" line and zero or more SDP attributes associated by an SDP "m=" line and zero or more SDP attributes associated
with the "m=" line. A local address:port combination is with the "m=" line. A local address:port combination is
assigned to each "m=" section. assigned to each "m=" section.
5-tuple: A collection of the following values: source address, 5-tuple: A collection of the following values: source address,
source port, destination address, destination port, and source port, destination address, destination port, and
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B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
for Real-Time Transport Protocol (RTP) Sources", RFC 7656, for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
DOI 10.17487/RFC7656, November 2015, DOI 10.17487/RFC7656, November 2015,
<https://www.rfc-editor.org/info/rfc7656>. <https://www.rfc-editor.org/info/rfc7656>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657, (Diffserv) and Real-Time Communication", RFC 7657,
DOI 10.17487/RFC7657, November 2015, DOI 10.17487/RFC7657, November 2015,
<https://www.rfc-editor.org/info/rfc7657>. <https://www.rfc-editor.org/info/rfc7657>.
[RFC8829] Uberti, J., Jennings, C., and E. Rescorla, Ed.,
"JavaScript Session Establishment Protocol (JSEP)",
RFC 8829, DOI 10.17487/RFC8829, January 2021,
<https://www.rfc-editor.org/info/rfc8829>.
[RFC8838] Ivov, E., Uberti, J., and P. Saint-Andre, "Trickle ICE: [RFC8838] Ivov, E., Uberti, J., and P. Saint-Andre, "Trickle ICE:
Incremental Provisioning of Candidates for the Interactive Incremental Provisioning of Candidates for the Interactive
Connectivity Establishment (ICE) Protocol", RFC 8838, Connectivity Establishment (ICE) Protocol", RFC 8838,
DOI 10.17487/RFC8838, January 2021, DOI 10.17487/RFC8838, January 2021,
<https://www.rfc-editor.org/info/rfc8838>. <https://www.rfc-editor.org/info/rfc8838>.
Appendix A. Design Considerations Appendix A. Design Considerations
One of the main issues regarding the BUNDLE grouping extensions has One of the main issues regarding the BUNDLE grouping extensions has
been whether, in offers and answers, the same port value can be been whether, in offers and answers, the same port value can be
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