draft-ietf-mmusic-sdp-bundle-negotiation-05.txt   draft-ietf-mmusic-sdp-bundle-negotiation-06.txt 
MMUSIC Working Group C. Holmberg MMUSIC Working Group C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track H. Alvestrand Updates: 3264 (if approved) H. Alvestrand
Expires: April 17, 2014 Google Intended status: Standards Track Google
C. Jennings Expires: October 9, 2014 C. Jennings
Cisco Cisco
October 14, 2013 April 7, 2014
Multiplexing Negotiation Using Session Description Protocol (SDP) Port Multiplexing Negotiation Using Session Description Protocol (SDP) Port
Numbers Numbers
draft-ietf-mmusic-sdp-bundle-negotiation-05.txt draft-ietf-mmusic-sdp-bundle-negotiation-06.txt
Abstract Abstract
This specification defines a new SDP Grouping Framework extension, This specification defines a new SDP Grouping Framework extension,
"BUNDLE", that can be used with the Session Description Protocol "BUNDLE", that can be used with the Session Description Protocol
(SDP) Offer/Answer mechanism to negotiate the usage of bundled media, (SDP) Offer/Answer mechanism to negotiate the usage of bundled media,
which refers to the usage of a single 5-tuple for media associated which refers to the usage of a single 5-tuple for sending and
with multiple SDP media descriptions ("m=" lines). receiving media associated with multiple SDP media descriptions ("m="
lines).
This specification also updates sections 5.1, 8.1 and 8.2 of RFC
3264, in order to allow an answerer to in an SDP answer assign a non-
zero port value to an "m=" line, even if the offerer in the
associated SDP offer had assigned a zero port value to the "m=" line.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 17, 2014. This Internet-Draft will expire on October 9, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 6
5. SDP Grouping Framework BUNDLE Extension Semantics . . . . . . 5 5. SDP Grouping Framework BUNDLE Extension Semantics . . . . . . 6
6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . 6
6.2. Bundled SDP Information . . . . . . . . . . . . . . . . . 5 5.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 6
6.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 5 5.2.2. SDP Information Considerations . . . . . . . . . . . 7
6.2.2. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . 6 5.2.3. Generating the Initial Offer . . . . . . . . . . . . 7
6.2.3. rtcp-mux Attribute . . . . . . . . . . . . . . . . . 6 5.2.4. Generating the Answer . . . . . . . . . . . . . . . . 8
6.2.4. rtcp Attribute . . . . . . . . . . . . . . . . . . . 6 5.2.5. Offerer Processing of the Answer . . . . . . . . . . 10
6.2.5. DTLS-SRTP fingerprint Attribute . . . . . . . . . . . 6 5.2.6. Modifying the Session . . . . . . . . . . . . . . . . 11
6.2.6. SDES crypto Attribute . . . . . . . . . . . . . . . . 6 6. SDP 'bundle-only' Attribute . . . . . . . . . . . . . . . . . 13
6.2.7. Other Attributes (a=) . . . . . . . . . . . . . . . . 6 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.3. RFC 5888 restrictions . . . . . . . . . . . . . . . . . . 6 6.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . 13
6.4. SDP Offerer Procedures . . . . . . . . . . . . . . . . . 7 6.2.1. Generating the Initial Offer . . . . . . . . . . . . 13
6.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 7 6.2.2. Generating the Answer . . . . . . . . . . . . . . . . 13
6.4.2. Request BUNDLE address selection . . . . . . . . . . 8 6.2.3. Offerer Processing of the Answer . . . . . . . . . . 14
6.4.3. Bundle Address Synchronization (BAS) . . . . . . . . 8 6.2.4. Modifying the Session . . . . . . . . . . . . . . . . 14
6.4.4. Adding a media description to a BUNDLE group . . . . 8 7. Protocol Identification . . . . . . . . . . . . . . . . . . . 14
6.4.5. Moving A Media Description Out Of A BUNDLE Group . . 9 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.4.6. Disabling A Media Description In A BUNDLE Group . . . 9 7.2. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 15
6.5. SDP Answerer Procedures . . . . . . . . . . . . . . . . . 9 8. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.5.1. Offerer Bundle Address Selection . . . . . . . . . . 10 8.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 15
6.5.2. Anwerer Bundle Address Selection . . . . . . . . . . 10 8.1.1. General . . . . . . . . . . . . . . . . . . . . . . . 15
6.5.3. Moving A Media Description Out Of A BUNDLE Group . . 10 8.1.2. Payload Type (PT) Value Re-usage . . . . . . . . . . 16
6.5.4. Rejecting A Media Description In A BUNDLE Group . . . 11 8.2. Associating RTP Packets With Correct SDP Media
7. Single vs Multiple RTP Sessions . . . . . . . . . . . . . . . 11 Description . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . . 17
7.2. Single RTP Session . . . . . . . . . . . . . . . . . . . 11 8.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 17
8. Usage With ICE . . . . . . . . . . . . . . . . . . . . . . . 12 8.3.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . 17
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 12 9. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 19
8.2. Candidates . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.3. Candidates . . . . . . . . . . . . . . . . . . . . . . . 12 9.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9.2.1. Generating the Initial Offer . . . . . . . . . . . . 19
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.2.2. Generating the Answer . . . . . . . . . . . . . . . . 20
10.1. Example: Bundle Address Selection . . . . . . . . . . . 13 9.2.3. Offerer Processing of the Answer . . . . . . . . . . 20
10.2. Example: Bundle Mechanism Rejected . . . . . . . . . . . 14 9.2.4. Modifying the Session . . . . . . . . . . . . . . . . 20
10.3. Example: Offerer Adds A Media Description To A BUNDLE 9.2.5. Keep-alives . . . . . . . . . . . . . . . . . . . . . 20
Group . . . . . . . . . . . . . . . . . . . . . . . . . 15 10. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 20
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 20
10.4. Example: Offerer Moves A Media Description Out Of A 10.2. Original text of section 5.1 (2nd paragraph) of RFC 3264 20
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 17 10.3. New text replacing section 5.1 (2nd paragraph) of RFC
10.5. Example: Offerer Disables A Media Description In A 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 21
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 19 10.4. Original text of section 8.2 (2nd paragraph) of RFC 3264 21
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 10.5. New text replacing section 8.2 (2nd paragraph) of RFC
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.6. Original text of section 8.4 (6th paragraph) of RFC 3264 22
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.7. New text replacing section 8.4 (6th paragraph) of RFC
14.1. Normative References . . . . . . . . . . . . . . . . . . 21 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 22
14.2. Informative References . . . . . . . . . . . . . . . . . 22 11. Security Considerations . . . . . . . . . . . . . . . . . . . 22
Appendix A. Design Considerations . . . . . . . . . . . . . . . 22 12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 22
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 22 12.1. Example: Bundle Address Selection . . . . . . . . . . . 22
A.2. UA Interoperability . . . . . . . . . . . . . . . . . . . 23 12.2. Example: Bundle Mechanism Rejected . . . . . . . . . . . 24
A.3. Usage of port number value zero . . . . . . . . . . . . . 24 12.3. Example: Offerer Adds A Media Description To A BUNDLE
A.4. B2BUA And Proxy Interoperability . . . . . . . . . . . . 25 Group . . . . . . . . . . . . . . . . . . . . . . . . . 25
A.4.1. Traffic Policing . . . . . . . . . . . . . . . . . . 25 12.4. Example: Offerer Moves A Media Description Out Of A
A.4.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 25 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 27
A.5. Candidate Gathering . . . . . . . . . . . . . . . . . . . 26 12.5. Example: Offerer Disables A Media Description Within A
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 29
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31
15. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 31
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
16.1. Normative References . . . . . . . . . . . . . . . . . . 33
16.2. Informative References . . . . . . . . . . . . . . . . . 33
Appendix A. Design Considerations . . . . . . . . . . . . . . . 34
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 34
A.2. UA Interoperability . . . . . . . . . . . . . . . . . . . 34
A.3. Usage of port number value zero . . . . . . . . . . . . . 36
A.4. B2BUA And Proxy Interoperability . . . . . . . . . . . . 36
A.4.1. Traffic Policing . . . . . . . . . . . . . . . . . . 37
A.4.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 37
A.5. Candidate Gathering . . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction 1. Introduction
In the IETF RTCWEB WG, a need to use a single 5-tuple for sending and In the IETF RTCWEB WG, a need to use a single 5-tuple for sending and
receiving media associated with multiple SDP media descriptions ("m=" receiving media associated with multiple SDP media descriptions ("m="
lines) has been identified. This would e.g. allow the usage of a lines) has been identified. This would e.g. allow the usage of a
single set of Interactive Connectivity Establishment (ICE) [RFC5245] single set of Interactive Connectivity Establishment (ICE) [RFC5245]
candidates for multiple media descriptions. Normally different media candidates for multiple media descriptions. Normally different media
types (audio, video etc) will be described using different media types (audio, video etc) will be described using different media
descriptions. descriptions.
This specification defines a new SDP Grouping Framework [RFC5888] This specification defines a new SDP Grouping Framework [RFC5888]
extension, "BUNDLE", that can be used with the Session Description extension, "BUNDLE", that can be used with the Session Description
Protocol (SDP) Offer/Answer mechanism [RFC3264] to negotiate the Protocol (SDP) Offer/Answer mechanism [RFC3264] to negotiate the
usage of bundled media, which refers to the usage of a single 5-tuple usage of bundled media, which refers to the usage of a single 5-tuple
for media associated with multiple SDP media descriptions ("m=" for sending and receiving media associated with multiple SDP media
lines). descriptions ("m=" lines).
The Offerer and Answerer [RFC3264] use the BUNDLE mechanism to The offerer and answerer [RFC3264] use the BUNDLE mechanism to
negotiate a single BUNDLE address to be used for the bundled media negotiate BUNDLE addresses, one for the offerer (offerer BUNDLE
associated with a BUNDLE group. address) and one for the answerer (answerer BUNDLE address) to be
used for the bundled media associated with a BUNDLE group.
The BUNDLE mechanism allows an SDP Offerer and SDP Answerer to assign Once it is known that both the offerer and the answerer supports the
identical addresses to multiple "m=" lines, if those "m=" lines are BUNDLE mechanism, a BUNDLE group and the associated BUNDLE addresses
associated with a BUNDLE group. However, until it is known whether have been negotiated, each endpoint can assign its BUNDLE address to
both the Offerer and Answerer support the BUNDLE mechanism, unique each "m=" line within, and use the address to send and receive all
addresses are assigned to each "m=" line, including those associated media associated with, the BUNDLE group.
with a BUNDLE group.
NOTE: As defined in RFC 4566 [RFC4566], the semantics of multiple NOTE: As defined in RFC 4566 [RFC4566], the semantics of assigning
"m=" lines using the same port number value are undefined, and there the same port value to multiple "m=" lines are undefined, and there
is no grouping defined by such means. Instead, an explicit grouping is no grouping defined by such means. Instead, an explicit grouping
mechanism needs to be used to express the intended semantics. This mechanism needs to be used to express the intended semantics. This
specification provides such extension. specification provides such an extension.
SDP Offers and SDP Answer can contain multiple BUNDLE groups. For SDP bodies can contain multiple BUNDLE groups. Each BUNDLE group
each BUNDLE group, a BUNDLE address is negotiated. Multiple BUNDLE MUST use a unique 5-tuple. Any given "m=" line can only be
groups cannot share the same bundle address. associated with a single BUNDLE group.
The procedures in this specification apply to a given BUNDLE group.
The default assumption is that all Real-Time Protocol (RTP) [RFC3550] The default assumption is that all Real-Time Protocol (RTP) [RFC3550]
based media flows within a BUNDLE group belongs to the same RTP based media flows associated with a BUNDLE group belong to the same
Session [RFC3550]. Future extensions can change that assumption. RTP Session [RFC3550]. Future extensions can change that assumption.
The BUNDLE mechanism is backward compatible. Endpoints that do not The BUNDLE mechanism is backward compatible. Endpoints that do not
support the BUNDLE mechanism are expected to generate SDP Offers and support the BUNDLE mechanism are expected to generate SDP offers and
SDP Answers without an SDP group:BUNDLE attribute, and are expected SDP answers without an SDP 'group:BUNDLE' attribute, and are expected
to assign unique addresses to each "m=" line, according to the to assign a unique address to each "m=" line within an SDP offer and
procedures in [RFC4566] and [RFC3264] SDP answer, according to the procedures in [RFC4566] and [RFC3264]
This specification also updates sections 5.1, 8.1 and 8.2 of
[RFC3264], in order to allow an answerer to assign a non-zero port
value to an "m=" line in an SDP answer, even if the offerer in the
associated SDP offer had assigned a zero port value to the "m=" line.
2. Terminology 2. Terminology
5-tuple: A collection of the following values: source address, source 5-tuple: A collection of the following values: source address, source
port, destination address, destination port and protocol. port, destination address, destination port and protocol.
Bundled media: Two or more RTP streams using a single 5-tuple. The Unique address: An IP address and IP port combination that is
RTCP streams associated with the RTP streams also use a single assigned to a single "m=" line in an SDP offer or SDP answer.
5-tuple, which might be the same, but can also be different, as the
one used by the RTP streams.
Unique address: This refers to an IP address and IP port combination, Shared address: An IP address and IP port combination that is
that can only be associated with a single "m=" line within an SDP assigned to multiple "m=" lines in an SDP offer or SDP answer.
Session.
BUNDLE address: This refers to an IP address and IP port combination, Offerer suggested BUNDLE mid: The first mid value in a given SDP
that is associated with each "m=" line within a BUNDLE group, within 'group:BUNDLE' attribute mid list in an SDP offer.
an SDP Session. The zero IP port value BUNDLE address MUST NOT be
used in a BUNDLE address.
NOTE: "m=" lines that share a BUNDLE address MUST also share other Answerer selected BUNDLE mid: The first mid value in a given SDP
parameters related to the media transport plane, e.g. ICE candidate 'group:BUNDLE' attribute mid list in an SDP answer.
information.
Offerer BUNDLE address: Within a given BUNDLE group, an IP address
and IP port combination used by an offerer to send and receive all
media associated with each "m=" line within the BUNDLE group.
Answerer BUNDLE address: Within a given BUNDLE group, an IP address
and IP port combination used by an answerer to send and receive all
media associated with each "m=" line within the BUNDLE group.
BUNDLE group: A set of "m=" lines, created using an SDP offer/answer
exchange, for which a single 5-tuple is used to send and receive
media. Each endpoint uses its BUNDLE address, associated with the
BUNDLE group, to send and receive the media.
Bundled "m=" line: An "m=" line, in an SDP offer or SDP answer,
associated with a BUNDLE group.
Bundle-only "m=" line: An "m=" line, to which an SDP 'bundle-only'
attribute has been assigned.
Bundled media: All media associated with a BUNDLE group.
Initial SDP offer: The first SDP offer, in which the offerer
indicates that it wants to create a given BUNDLE group.
Subsequent SDP offer: An SDP offer which contains a BUNDLE group that
has been created as part of a previous SDP offer/answer exchange.
3. Conventions 3. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119 document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119]. [RFC2119].
4. Applicability Statement 4. Applicability Statement
The mechanism in this specification only applies to the Session The mechanism in this specification only applies to the Session
Description Protocol (SDP) [RFC4566], when used together with the SDP Description Protocol (SDP) [RFC4566], when used together with the SDP
Offer/Answer mechanism [RFC3264]. Offer/Answer mechanism [RFC3264].
5. SDP Grouping Framework BUNDLE Extension Semantics 5. SDP Grouping Framework BUNDLE Extension Semantics
5.1. General
This section defines a new SDP Grouping Framework extension, BUNDLE. This section defines a new SDP Grouping Framework extension, BUNDLE.
The BUNDLE extension can be indicated using an SDP session-level The BUNDLE extension can be indicated using an SDP session-level
'group' attribute. Each SDP Media Description ("m=" line) that is 'group' attribute. Each SDP Media Description ("m=" line) that is
grouped together, using SDP media-level mid attributes, belongs to a grouped together, using SDP media-level mid attributes, belongs to a
given BUNDLE group. given BUNDLE group.
6. SDP Offer/Answer Procedures 5.2. SDP Offer/Answer Procedures
6.1. General 5.2.1. General
This section describes the usage of the SDP Offer/Answer mechanism This section describes usage of the SDP offer/answer mechanism
[RFC3264] to negotiate the usage of the BUNDLE mechanism, to [RFC3264] for negotiating usage of the BUNDLE mechanism, for creating
negotiate the BUNDLE address, and to add, remove and reject SDP Media a BUNDLE group, for selecting the BUNDLE addresses (offerer BUNDLE
Descriptions ("m=" lines) [RFC4566] associated with a BUNDLE group. address and answerer BUNDLE address), for adding an "m=" line to a
BUNDLE group, for moving an "m=" line out of a BUNDEL group, and for
disabling an "m=" line within a BUNDLE group.
The generic rules and procedures defined in [RFC3264] and [RFC5888] The generic rules and procedures defined in [RFC3264] and [RFC5888]
apply when the SDP Offer/Answer mechanism is used with the BUNDLE also apply to the BUNDLE mechanism. For example, if an SDP offer is
mechanism. For example, if an SDP Offer is rejected, the previously rejected by the answerer, the previously negotiated SDP parameters
negotiated SDP parameters and characteristics (including those and characteristics (including those associated with a BUNDLE group)
associated with BUNDLE groups) apply. apply. Hence, if an offerer generates an SDP offer in which the
offerer wants to create a BUNDLE group, and the answerer rejects the
SDP offer, the BUNDLE group is not created.
When an endpoint, acting as an Offerer or Answerer [RFC3264], The procedures in this section are independent of the media type or
generates an SDP Offer, or an SDP Answer, the endpoint MUST assign an transport protocol represented by a bundled "m=" line. [Section 8]
SDP media-level mid value for each "m=" line in a BUNDLE group. In defines additional considerations for RTP based media. [Section 6]
addition, the endpoint MUST assign an SDP session-level group:BUNDLE defines additional considerations for the usage of the SDP 'bundle-
attribute for each BUNDLE group, and place each mid associated with only' attribute. [Section 9] defines additional considerations for
the SDP group:BUNDLE attribute mid list. the usage of Interactive Connectivity Establishment (ICE) mechanism
[RFC5245].
6.2. Bundled SDP Information 5.2.2. SDP Information Considerations
5.2.2.1. General
6.2.1. General
This section describes restrictions associated with the usage of SDP This section describes restrictions associated with the usage of SDP
parameters and extensions within a BUNDLE group. It also describes, parameters within a BUNDLE group. It also describes, when parameter
when parameter and attribute values have been assigned to each "m=" and attribute values have been assigned to each bundled "m=" line,
line in the BUNDLE group, how to calculate a value for the whole how to calculate a value for the whole BUNDLE group.
BUNDLE group.
6.2.2. Bandwidth (b=) 5.2.2.2. Connection Data (c=)
The "c=" line nettype value [RFC4566] assigned to a bundled "m=" line
MUST be 'IN'.
The "c=" line addrtype value [RFC4566] assigned to a bundled "m="
line MUST be 'IP4' or 'IP6'. The same value MUST be assigned to each
"m=" line.
NOTE: Extensions to this specification can specify usage of the
BUNDLE mechanism for other nettype and addrtype values than the ones
listed above.
5.2.2.3. Bandwidth (b=)
The total proposed bandwidth is the sum of the proposed bandwidth for The total proposed bandwidth is the sum of the proposed bandwidth for
each "m=" line associated with a negotiated BUNDLE group. each bundled "m=" line.
6.2.3. rtcp-mux Attribute 5.2.2.4. Attributes (a=)
For each "m=" line in a BUNDLE group, an Offerer and Answerer MUST [I-D.nandakumar-mmusic-sdp-mux-attributes] defines rules and
assign an SDP rtcp-mux attribute [RFC5761]. restrictions for assigning different types of SDP attributes to a
bundled "m=" line.
6.2.4. rtcp Attribute 5.2.3. Generating the Initial Offer
When used, for each RTP media "m=" line in a BUNDLE group, an Offerer 5.2.3.1. General
and Answerer MUST assign an SDP rtcp attribute [RFC3605] with an
identical attribute value.
6.2.5. DTLS-SRTP fingerprint Attribute When an offerer generates an initial SDP offer, in order to create a
BUNDLE group, the offerer MUST in the SDP offer assign a unique
address to each "m=" line with a non-zero port value, following the
procedures in [RFC3264].
When DTLS-SRTP is used, for each RTP media "m=" line in a BUNDLE The offerer MUST in the SDP offer insert an SDP session level
group, an Offerer and Answerer MUST assign an SDP DTLS-SRTP 'group:BUNDLE' attribute, associated with the BUNDLE group, and
fingerprint attribute with identical attribute values. assign an SDP 'mid' attribute [RFC5888] to each "m=" line that the
offerer wants to be within the BUNDLE group, and place the 'mid'
attribute value in the 'group:BUNDLE' attribute mid list.
6.2.6. SDES crypto Attribute [Section 12.1] shows an example of an initial SDP offer.
When SDES is used, for each RTP media "m=" line in a BUNDLE group, an 5.2.3.2. Request offerer BUNDLE address selection
Offerer and Answerer MUST assign an SDP crypto attribute, with unique
attribute values.
6.2.7. Other Attributes (a=) When an offerer generates an initial SDP offer, in order to create a
BUNDLE group, the offerer MUST in the SDP offer indicate which unique
address, associated with one of the "m=" lines that the offerer wants
to be within the BUNDLE group, that the offerer wants the answerer to
select as the offerer BUNDLE address [Section 5.2.4.2]. In the SDP
offer, the offerer BUNDLE mid value represents that address.
There are also special rules for handling many different attributes 5.2.4. Generating the Answer
as defined in [I-D.nandakumar-mmusic-sdp-mux-attributes]. It might
not possible to use bundle with some attributes.
6.3. RFC 5888 restrictions 5.2.4.1. RFC 5888 restrictions
Based on the rules and procedures in [RFC5888], the following When an answerer generates an SDP answer, the following restrictions,
restrictions also apply to BUNDLE groups in SDP Answers: defined in [RFC5888], also apply a BUNDLE group:
o 1) A BUNDLE group must not be added to an SDP Answer, unless the o 1) The answerer MUST NOT in the SDP answer include a BUNDLE group,
same BUNDLE group was included in the associated SDP Offer; and unless the offerer in the associated SDP offer requested the
BUNDLE group to be created; and
o 2) An SDP "m=" line must not be added to a BUNDLE group in the SDP o 2) The answerer MUST NOT in the SDP answer include an "m=" line
Answer, unless it was in the same BUNDLE group in the associated within a BUNDLE group, unless the offerer in the associated SDP
SDP Offer. offer requested the "m=" line to be within the BUNDLE group.
6.4. SDP Offerer Procedures 5.2.4.2. Answerer Selection of Offerer Bundle Address
6.4.1. General When an answerer generates an SDP answer, it MUST select a BUNDLE
address for the offerer, referred to as the offerer BUNDLE address.
The answerer MUST select an address which the offerer in the
associated SDP answer requested to be within the BUNDLE group.
When an Offerer generates an Offer, it assigns an address to each In the SDP offer, the offerer suggested BUNDLE mid represents the
"m=" line, according to the procedures in [RFC3264]. To each "m=" "m=" line to which the offerer in the SDP offer has assigned the
line within a BUNDLE group the Offerer assigns either an address that address that it wants the answerer to select as the offerer BUNDLE
is unique to that "m=" line, or a shared address that is also address [Section 5.2.3.2]. The answerer MUST first select the "m="
assigned to other "m=" lines within the BUNDLE group. Such shared line associated with the offerer suggested BUNDLE mid, and check
address can be, but does not have to be, a previously selected BUNDLE whether it fulfils the following criteria:
address Section 6.5.1.
OPEN ISSUE (Q6): There is a discussion on whether assigning a shared o The answerer will in the SDP answer create the BUNDLE group;
address to multiple "m=" lines shall be allowed until the Answerer o The answerer will not in the SDP answer move the "m=" line out of
has indicated support of BUNDLE. the BUNDLE group [Section 5.2.4.4];
o (http://www.ietf.org/mail-archive/web/mmusic/current/ o The answerer will not in the SDP answer reject the "m=" line
msg12245.html) [Section 5.2.4.5]; and
The Offerer MUST NOT assign an address (unique or shared), that it o The offerer did not in the associated SDP offer assign a zero port
has assigned to an "m=" line within a BUNDLE group, to an "m=" line value to the "m=" line.
outside the BUNDLE group.
The Offerer MUST, for a BUNDLE group, on the SDP session level If all of the criteria above is fulfilled, the answerer MUST select
[RFC4566], insert an SDP group:BUNDLE attribute associated with the the address associated with the "m=" line as the offerer BUNDLE
BUNDLE group. The Offerer MUST assign an SDP 'mid' attribute address.
[RFC5888] to each "m=" line within the BUNDLE group, and place the
mid value in the group:BUNDLE attribute mid list.
The Offerer MAY assign an SDP 'bundle-only' attribute [ref-to-be- If all of the criteria is not fulfilled, the answerer MUST select the
added] to one or more "m=" lines within a BUNDLE group. next mid value in the mid list, and perform the same criteria check
for the "m=" line associated with the mid value.
OPEN ISSUE (Q8): It still needs to be decided whether a zero port In the SDP answer, the answerer selected BUNDLE mid value represents
value can be assigned to a 'bundle-only' "m=" line. the "m=" line which address (in the associated SDP offer) the
answerer has selected as the offerer BUNDLE address.
o (http://www.ietf.org/mail-archive/web/mmusic/current/ [Section 12.1] shows an example of an offerer BUNDLE address
msg12075.html) selection.
o (http://www.ietf.org/mail-archive/web/mmusic/current/ 5.2.4.3. Answerer Selection of Answerer BUNDLE Address
msg12226.html)
o (http://www.ietf.org/mail-archive/web/mmusic/current/ When an answerer generates an SDP answer, the answerer MUST select a
msg12339.html) BUNDLE address for itself, referred to as the answerer BUNDLE
address, and in the SDP answer assign the answerer BUNDLE address to
each "m=" line within the created BUNDLE group.
6.4.2. Request BUNDLE address selection The answerer MUST NOT in the SDP answer assign the answerer BUNDLE
address to an "m=" line that is not associated with the BUNDLE group,
or to an "m=" line that is associated with another BUNDLE group.
When an Offerer generates an Offer, it MUST indicate which address The answerer is allowed to select a new answerer BUNDLE address in
(unique or shared) within a BUNDLE group it wishes the Answer to every SDP answer that the answerer generates.
select as the Offerer's BUNDLE address for the BUNDLE group
Section 6.5.1. The Offerer MUST do this even if the Answerer has, in
a previous Answer within the dialog, already selected the Offerer's
BUNDLE address.
In order to request an address (unique or shared) to be selected as [Section 12.1] shows an example of an answerer BUNDLE address
the Offerer's BUNDLE address for a BUNDLE group, the Offerer places selection.
the mid value, associated with the "m=" line representing the
requested address, first in the SDP group:BUNDLE attribute mid list
associated with the BUNDLE group.
Section 10.1 shows an example of a Bundle Address Request. 5.2.4.4. Moving A Media Description Out Of A BUNDLE Group
6.4.3. Bundle Address Synchronization (BAS) When an answerer generates an SDP answer, in which the answerer moves
a bundled "m=" line out a BUNDLE group, the answerer assigns an
address to the moved "m=" line based on the type of address that the
offerer in the associated SDP offer assigned to the "m=" line.
When an Offerer receives an Answer, in which an offered BUNDLE group o If the offerer in the SDP offer has assigned a shared address
is accepted, if the Offerer in the associated Offer assigned an (e.g. a previously selected offerer BUNDLE address) to the "m="
address (unique or shared), that does not represent the BUNDLE line, the answerer MUST in the SDP answer reject the moved "m="
address selected for the Offerer, to an "m=" line within the BUNDLE line, according to the procedures in [Section 5.2.4.5].
group, the Offerer MUST send a subsequent Offer, in which it assigns
the BUNDLE address selected for the Offerer to each "m=" line within
the BUNDLE group. This procedure is referred to as Bundle Address
Synchronization (BAS), and the Offer is referred to as a BAS Offer.
The Offerer MAY modify any SDP parameter in a BAS Offer. o If the offerer in the SDP offer assigned an SDP 'bundle-only'
attribute to the "m=" line, the answerer MUST in the SDP answer
reject the moved "m=" line, according to the procedures in
[Section 5.2.4.5].
NOTE: It is important that the BAS Offer gets accepted by the o If the offerer in the SDP offer assigned a unique address to the
Answerer, so the Offerer needs to consider the necessity to modify "m=" line, the answerer MUST in the SDP answer assign a unique
SDP parameters that could get the Answerer to reject the BAS Offer. address to the moved "m=" line.
Removing "m=" lines, or reducing the number of codecs, in the BAS
Offer used for the is considered to have a low risk of being
rejected.
NOTE: The main purpose of the BAS Offer is to make sure that In addition, in either case above, the answerer MUST NOT in the SDP
answer include a mid value, associated with the moved "m=" line, in
the SDP 'group:BUNDLE' attribute mid list associated with the BUNDLE
group.
5.2.4.5. Rejecting A Media Description In A BUNDLE Group
When an answerer generates an SDP answer, in which the answerer
rejects an "m=" line, the answerer MUST in the SDP answer assign an
address with a zero port value to the rejected "m=" line, according
to the procedures in [RFC4566].
In addition, the answerer MUST NOT in the SDP answer include a mid
value, associated with the rejected "m=" line, in the SDP
'group:BUNDLE' attribute mid list associated with the BUNDLE group.
5.2.5. Offerer Processing of the Answer
5.2.5.1. General
When an offerer receives an SDP answer, the offerer MUST apply the
selected offerer BUNDLE address to each bundled "m=" line. If the
offerer generates a subsequent SDP offer, the offerer MUST in the SDP
offer assign the offerer BUNDLE address to each bundled "m=" line
(including any 'bundle-only' "m=" line) [Section 5.2.6].
If the SDP answer does not contain a BUNDLE group, the offerer MUST
cease to use any procedure associated with the BUNDLE mechanism.
5.2.5.2. Bundle Address Synchronization (BAS)
If the selected offerer BUNDLE address is different than the address
that the offerer in the associated SDP offer assigned to a bundled
"m=" line (including an "m=" line that the offerer in the SDP offer
added to an existing BUNDLE group [Section 5.2.6.2]), and the bundled
"m=" line was not rejected [Section 5.2.4.5], or moved out of the
BUNDLE group [Section 5.2.4.4] by the answerer, the offerer SHOULD as
soon as possible generate a subsequent SDP offer, in which the
offerer assigns the offerer BUNDLE address to each bundled "m=" line.
This procedure is referred to as Bundle Address Synchronization
(BAS), and the SDP offer is referred to as a BAS Offer.
The offerer MAY in the BAS offer modify any SDP parameter.
NOTE: It is important that the BAS offer gets accepted by the
answerer. For that reason the offerer needs to consider the
necessity to in the BAS offer modify SDP parameters that could get
the answerer to reject the BAS offer. Disabling "m=" lines, or
reducing the number of codecs, in a BAS offer is considered to have a
low risk of being rejected.
NOTE: The main purpose of the BAS offer is to ensure that
intermediaries, that might not support the BUNDLE mechanism, have intermediaries, that might not support the BUNDLE mechanism, have
correct information regarding which address is going to be used for correct information regarding the address is going to be used to
the bundled media. transport the bundled media.
Section 10.1 shows an example of an BAS Offer. [Section 12.1] shows an example where an offerer sends a BAS offer.
6.4.4. Adding a media description to a BUNDLE group 5.2.6. Modifying the Session
When an Offerer generates an Offer, in which it adds an "m=" line to 5.2.6.1. General
a BUNDLE group, the Offerer assigns an address (unique or shared) to
the "m=" line, assigns an SDP 'mid' attribute to the "m=" line, and
places the mid value in the group:BUNDLE attribute mid list
associated with the BUNDLE group, according to the procedures in
Section 6.4.2. If the Offerer wishes the Answerer to select the
address assigned to the added "m=" as the Offerer's BUNDLE address,
the mid value associated with the "m=" line is placed first in the
list, according to the procedures in Section 6.4.2.
Section 10.3 shows an example of an Offer used to add an "m=" line to When an offerer generates a subsequent SDP offer, the offerer MUST in
a BUNDLE group. the SDP offer assign the previously selected offerer BUNDLE address
[Section 5.2.4.2] to each bundled "m=" line (including any bundle-
only "m=" line), unless the offerer in the SDP offer moves the "m="
line out of the BUNDLE group [Section 5.2.6.3], or disables the "m="
line [Section 5.2.6.4].
6.4.5. Moving A Media Description Out Of A BUNDLE Group If the SDP offerer in the SDP offer adds an "m=" line to the BUNDLE
group [Section 5.2.6.2], the offerer MAY assign the previously
selected offerer BUNDLE address to the added "m=" line.
When an Offerer generates an Offer, in which an "m=" line is moved In addition, the offerer MUST in the SDP offer indicate which address
out of a BUNDLE group, the Offerer MUST assign a unique address to (unique or previously selected offerer BUNDLE address) it wants the
the moved "m=" line. In addition, the Offerer MUST NOT anymore answerer to select as the offerer BUNDLE address, following the
include a mid value, representing the "m=" line, in the SDP procedures in [Section 5.2.3.2]. The offerer MUST do this even if
group:BUNDLE attribute mid list associated with the BUNDLE group. the offerer in the SDP offer assigns a previously selected offerer
BUNDLE address to each bundled "m=" line.
Section 10.4 shows an example of an Offer used to move an "m=" line 5.2.6.2. Adding a media description to a BUNDLE group
out of a BUNDLE group.
6.4.6. Disabling A Media Description In A BUNDLE Group When an offerer generates an SDP offer, in which the offerer wants to
add an "m=" line to a BUNDLE group, the offerer assigns in the SDP
offer an address (unique or previously selected offerer BUNDLE
address) to the "m=" line, assigns an SDP 'mid' attribute to the "m="
line, and places the mid value in the SDP 'group:BUNDLE' attribute
mid list associated with the BUNDLE group [Section 5.2.3.2].
When an Offerer generates an Offer, in which an "m=" line associated NOTE: If the offerer wants that the answerer selects the address
with a BUNDLE group is disabled, the Offerer MUST assign an address associated with the added "m=" as the offerer BUNDLE address, the
with a zero port value [RFC4566] to the disabled "m=" line. In offerer suggested BUNDLE mid MUST represent the added "m=" line
addition, the Offerer MUST NOT anymore include a mid value, [Section 5.2.3.2].
representing the "m=" line, in the SDP group:BUNDLE attribute mid
list associated with the BUNDLE group.
OPEN ISSUE (Q8): It still needs to be decided whether a zero port [Section 12.3] shows an example where an offerer sends an SDP offer
value can be assigned to a 'bundle-only' "m=" line. in order to add an "m=" line to a BUNDLE group.
o (http://www.ietf.org/mail-archive/web/mmusic/current/ 5.2.6.3. Moving A Media Description Out Of A BUNDLE Group
msg12075.html)
o (http://www.ietf.org/mail-archive/web/mmusic/current/ When an offerer generates an SDP offer, in which the offerer wants to
msg12226.html) move a bundled "m=" line out of a BUNDLE group, the offerer MUST
assign a unique address to the "m=" line. In addition, the offerer
MUST NOT place a mid value associated with the "m=" line in the SDP
'group:BUNDLE' attribute mid list associated with the BUNDLE group.
o (http://www.ietf.org/mail-archive/web/mmusic/current/ NOTE: The offerer MAY keep a previously assigned SDP 'mid' attribute
msg12339.html) in an "m=" line that it wants to move out of a BUNDLE group, e.g. if
the mid value is used for some other SDP grouping extension than
BUNDLE.
Section 10.5 shows an example of an Offer used to disable an "m=" [Section 12.4] shows an example where an offerer sends an SDP offer
line in a BUNDLE group. in order to move an "m=" line out of a BUNDLE group.
6.5. SDP Answerer Procedures 5.2.6.4. Disabling A Media Description In A BUNDLE Group
6.5.1. Offerer Bundle Address Selection
When an Answerer generates an Answer that contains a BUNDLE group, When an offerer generates an SDP offer, in which the offerer wants to
the Answer MUST select the Offerer's BUNDLE address. The first mid disable a bundled "m=" line, the offerer MUST assign an address with
value in the SDP group:BUNDLE attribute mid list of the Offer a zero port alue to the "m=" line, following the procedures in
represents the address which the Offerer wishes the Answer to select [RFC4566]. In addition, the offerer MUST NOT place a mid value
as the Offerer's BUNDLE address Section 6.4.2. associated with the "m=" line in the SDP 'group:BUNDLE' attribute mid
list associated with the BUNDLE group.
The Answerer SHOULD select the address represented by the first mid NOTE: The offerer MAY assign an SDP 'mid' attribute to an "m=" line
value, unless the Answerer in the associated Answer will reject the that it wants to disable, e.g. if the mid value is used for some
"m=" line associated with the mid value, or remove the "m=" line from other SDP grouping extension than BUNDLE.
the BUNDLE group. In such case the Answerer MUST select an address
associated with the first unrejected mid value that remains in the
SDP group:BUNDLE attribute mid list of the Offer.
In the SDP Answer, the Answerer MUST place the mid value associated [Section 12.5] shows an example where an offerer sends an SDP offer
with the selected Offerer's BUNDLE address first in the SDP in order to disable an "m=" line within a BUNDLE group.
group:BUNDLE attribute mid list associated with the BUNDLE group.
Section 10.1 shows an example of an Offerer's BUNDLE address 6. SDP 'bundle-only' Attribute
selection.
6.5.2. Anwerer Bundle Address Selection 6.1. General
When an Answerer creates an Answer that contains a BUNDLE group, the This section defines a new SDP media-level attribute [RFC4566],
Answerer MUST assign a local shared address, the Answerer's BUNDLE 'bundle-only'. An offerer can in an SDP offer assign a 'bundle-only'
address, to each "m=" line within the BUNDLE group. "m=" line to a bundled "m=" line (including an "m=" line that the
offerer wants to add to the BUNDLE group [Section 5.2.6.2]), in order
to ensure that the answerer only accepts the "m=" line if the
answerer supports the BUNDLE mechanism, and if the answerer in the
SDP answer keeps the "m=" line within the BUNDLE group.
The Answerer is allowed to change its BUNDLE address in any SDP 6.2. SDP Offer/Answer Procedures
Answer.
The Answerer MUST NOT assign a shared address, that it has assigned 6.2.1. Generating the Initial Offer
to an "m=" line within a BUNDLE group, to an "m=" line outside the
BUNDLE group.
Section 10.1 shows an example of an Answerer's local BUNDLE address When an offerer generates an initial SDP offer, in order to create a
selection. BUNDLE group, the offerer can in the SDP offer assign an SDP 'bundle-
only' attribute to an "m=" line that the offerer wants to be within
the BUNDLE group.
6.5.3. Moving A Media Description Out Of A BUNDLE Group The offerer MUST in the SDP offer assign a zero port value the
bundle-only "m=" line.
When an Answerer generates an Answer, in which an "m=" line is moved 6.2.2. Generating the Answer
out of a BUNDLE group, the Answerer assigns an address to the moved
"m=" line based on the type of address that the Offerer assigned to
the associated "m=" line in the associated Offer, as described below.
If the Offerer assigned a shared address to the "m=" line, the When the answerer selects the offerer BUNDLE address
answerer MUST reject the moved "m=" line, according to the procedures [Section 5.2.4.2], the answerer MUST also take a bundle-only "m="
in Section 6.5.4. line with a non-zero port value into consideration.
If the Offerer assigned an SDP 'bundle-only' attribute to the "m=" If the offerer in the SDP offer has assigned a zero port value to a
line, the Answerer MUST reject the moved "m=" line, according to the bundle-only "m=" line, and if the answerer accepts the "m=" line, the
procedures in Section 6.5.4. answerer will treat the "m=" line as any other bundle "m=" line when
the answerer generates the SDP answer [Section 5.2.4].
If the Offerer assigned a unique address to the "m=" line, the Answer NOTE: If the offerer in the SDP offer has assigned a zero port value
MUST assign a unique address to the moved "m=" line. to a bundled "m=" line, but the offerer has not assigned a 'bundle-
only' SDP attribute to the "m=" line, it is an indication that the
offerer wants to disable the "m=" line [Section 5.2.6.4].
In addition, in either case above, the Answerer MUST NOT anymore If the answerer in the SDP answer does not keep the bundle-only "m="
include a mid value, representing the "m=" line, in the SDP line within the BUNDLE group, the answerer MUST in the SDP answer
group:BUNDLE attribute list associated with the BUNDLE group. reject the "m=" line [Section 5.2.4.5].
6.5.4. Rejecting A Media Description In A BUNDLE Group The answerer MUST NOT in the SDP answer assign an SDP 'bundle-only'
attribute to an "m=" line (even if the offerer in the associated SDP
offer has assigned a 'bundle-only' attribute to the "m="line).
When an Answerer generates an Answer, in which an "m=" line 6.2.3. Offerer Processing of the Answer
associated with a BUNDLE group is rejected, the Answerer MUST assign
an address with a zero port value to the rejected "m=" line,
according to the procedures in [RFC4566]. In addition, the Answerer
MUST NOT anymore include a mid value, representing the "m=" line, in
the SDP group:BUNDLE attribute midlist associated with the BUNDLE
group.
7. Single vs Multiple RTP Sessions When the offerer receives an SDP answer, the offerer follows the
procedures in [Section 5.2.5]. If the offerer in the associated SDP
offer assigned an SDP 'bundle-only' attribute to an "m=" line, and
the "m=" line was accepted (and was kept within the BUNDLE group) by
the answerer, the selected offerer BUNDLE address also applies to the
"m=" line.
6.2.4. Modifying the Session
When an offerer creates a subsequent SDP offer, the offerer follows
the procedures in [Section 5.2.6]. If the offerer in the SDP offer
assigns an SDP 'bundle-only' attribute to a bundled "m=" line, in
order to ensure that the answerer accepts the "m=" line only if the
answerer keeps the "m=" line within the BUNDLE group, the offerer
MUST NOT assign a zero port value to the "m=" line. Instead, the
offerer MUST in the SDP offer assign the offerer BUNDLE address or,
if the "m=" line is added to the BUNDLE group [Section 5.2.6.2],
either the offerer BUNDLE address or a unique address, to the "m="
line.
NOTE: The offerer can in a subsequent SDP offer assign an SDP
'bundle-only' attribute to a bundled "m=" line even if the offerer
did not assign a 'bundle-only' attribute to the "m=" line in a
previous SDP offer.
If the offerer in the SDP offer wants to move a bundled "m=" line out
of a BUNDLE group [Section 5.2.6.3], the offerer MUST NOT in the SDP
offer assign a 'bundle-only' attribute to the "m=" line.
If the offerer in the SDP offer wants to disable a bundled "m=" line
[Section 5.2.6.4], the offerer MUST NOT in the SDP offer assign a
'bundle-only' attribute to the "m=" line.
7. Protocol Identification
7.1. General 7.1. General
By default, all RTP based media flows within a given BUNDLE group If bundled "m=" lines represent different transport protocols, there
belong to a single RTP session [RFC3550]. Multiple BUNDLE groups MUST exist a specification which describes a mechanism, for this
will form multiple RTP Sessions. specific transport protocol combination, how to associate a received
packet with the correct transport protocol.
The usage of multiple RTP Sessions within a given BUNDLE group, or In addition, if a received packet can be associated with more than
the usage of a single RTP Session that spans over multiple BUNDLE one bundled "m=" line, there MUST exist a specification which
describes a mechanism how to associated the received packet with the
correct "m=" line.
7.2. STUN, DTLS, SRTP
Section 5.1.2 of [RFC5764] describes a mechanism how to identify the
protocol among the STUN, DTLS and SRTP protocols (in any
combination). If an offer or answerer in SDP offers or answers
include bundled "m=" lines that represent these protocols, the
offerer or answerer MUST support the mechanism described in
[RFC5764], and no explicit negotiation is required in order to
indicate support and usage of the mechanism.
[RFC5764] does not describe how to identify different protocols
transported on DTLS, only how to identify the DTLS protocol itself.
If multiple protocols are transported on DTLS, there MUST exist a
specification describing a mechanism how to identify each individual
protocol. In addition, if a received DTLS packet can be associated
with more than one "m=" line, there MUST exist a specification which
describes a mechanism how to associate the received DTLS packet with
the correct "m=" line.
[Section 8.2] describes how to associate a received (S)RTP packet
with the correct "m=" line.
8. RTP Considerations
8.1. Single RTP Session
8.1.1. General
By default, all RTP based media within a BUNDLE group belong to a
single RTP session [RFC3550]. Multiple BUNDLE groups will form
multiple RTP Sessions.
NOTE: The usage of multiple RTP sessions within a BUNDLE group, or
the usage of a single RTP session that spans over multiple BUNDLE
groups, is outside the scope of this specification. Other groups, is outside the scope of this specification. Other
specification needs to extend the BUNDLE mechanism in order to allow specification needs to extend the BUNDLE mechanism in order to allow
such usages. such usages.
7.2. Single RTP Session When a single RTP session is used, all bundled "m=" lines
representing RTP based media share a single SSRC numbering space
When a single RTP Session is used, media associated with all "m=" [RFC3550].
lines part of a bundle group share a single SSRC [RFC3550] numbering
space.
In addition, the following rules and restrictions apply for a single In addition, the following rules and restrictions apply for a single
RTP Session: RTP session:
o The dynamic payload type values used in the "m=" lines MUST NOT o A specific payload type value can be used in multiple bundled "m="
overlap. lines if each codec associated with the payload type number shares
an identical codec configuration [Section 8.1.2].
o The "proto" value in each "m=" line MUST be identical (e.g. RTP/ o The "proto" value in each bundled "m=" line MUST be identical
AVPF). (e.g. RTP/AVPF).
o A given SSRC SHOULD NOT transmit RTP packets using payload types o A given SSRC SHOULD NOT transmit RTP packets using payload types
that originates from different "m=" lines. that originates from different bundled "m=" lines.
NOTE: The last bullet above is to avoid sending multiple media types NOTE: The last bullet above is to avoid sending multiple media types
from the same SSRC. If transmission of multiple media types are done from the same SSRC. If transmission of multiple media types are done
with time overlap RTP and RTCP fails to function. Even if done in with time overlap RTP and RTCP fails to function. Even if done in
proper sequence this causes RTP Timestamp rate switching issues [ref proper sequence this causes RTP Timestamp rate switching issues [ref
to draft-ietf-avtext-multiple-clock-rates]. to draft-ietf-avtext-multiple-clock-rates].
8. Usage With ICE 8.1.2. Payload Type (PT) Value Re-usage
8.1. General Multiple bundled "m=" lines might represent RTP based media. As all
RTP based media associated with a BUNDLE group belong to the same RTP
session, in order for a given payload type value to used inside more
than one bundled "m=" line, all codecs associated with the payload
type numbers MUST share an identical codec configuration. This means
that the codecs MUST share the same media type, encoding name, clock
rate and any parameter that can affect the codec configuration and
packetization. [I-D.nandakumar-mmusic-sdp-mux-attributes] lists SDP
attributes, which attribute values must be identical for all codecs
that use the same payload type value.
8.2. Associating RTP Packets With Correct SDP Media Description
In general, there are multiple mechanisms that can be used by an
endpoint in order to associate received RTP packets with the bundled
"m=" line representing the RTP packets. Such mechanisms include
using the local address:port combination on which the RTP packets are
received, the payload type value carried inside the RTP packets, the
SSRC values carried inside the RTP packets, and other "m=" line
specific information carried inside the RTP packets.
As all RTP packets associated with a BUNDLE group are sent and
received using the same 5-tuple, the local address:port combination
cannot be used to associate received RTP packets with the correct
"m=" line.
As described in [Section 8.1.2], the same payload type value might be
used inside RTP packets described by multiple "m=" lines. In such
cases, the payload type value cannot be used to associate received
RTP packets with the correct "m=" line.
An offerer and answerer can in an SDP offer and answer inform each
other which SSRC values they will use inside sent RTP packets by, by
assigning an SDP 'ssrc' attribute [RFC5576] to each bundled "m=" line
which contains a payload type value that is also used inside another
bundled "m=" line. As the SSRC values will be carried inside the RTP
packets, the offerer and answerer can then use that information to
associate received RTP packets with the correct "m=" line. However,
an offerer will not know which SSRC values the answerer will use
until it has received the SDP answer providing that information. Due
to this, before the offerer has received the SDP answer, the offerer
will not be able to associate received RTP packets with the correct
"m=" line using the SSRC values.
In order for an offerer and answerer to always be able to associate
received RTP packets with the correct "m=" line, the offerer and
answerer MUST in an SDP offer and answer assign an SDP "receiver-id"
attribute [receiver-id-reference-to-be-added] to each bundled "m="
line which contains a payload type value that is also used inside
another bundled "m=" line. If an answerer accepts such "m=" line,
and keeps it within the BNDLE group, the answerer MUST insert the
'receiver-id' attribute value in RTP packets, associated with the
"m=" line, sent towards the offerer.
OPEN ISSUE: We need a mechanism that implements the 'receiver-id'
mechanism and the associated SDP attribute.
8.3. RTP/RTCP Multiplexing
8.3.1. General
When a BUNDLE group, which contains RTP based media, is created, the
offerer and answerer MUST negotiate whether to enable RTP/RTCP
multiplexing for the RTP based media associated with the BUNDLE group
[RFC5761].
If RTP/RTCP multiplexing is not enabled, separate 5-tuples will be
used for sending and receiving the RTP packets and the RTCP packets.
8.3.2. SDP Offer/Answer Procedures
8.3.2.1. General
This section describes how an offerer and answerer can use the SDP
'rtcp-mux' attribute [RFC5761] and the SDP 'rtcp' attribute [RFC3605]
to negotiate usage of RTP/RTCP multiplexing for RTP based associated
with a BUNDLE group.
8.3.2.2. Generating the Initial Offer
When an offerer generates an initial SDP offer, if the offerer wants
to negotiate usage of RTP/RTCP multiplexing within a BUNDLE group,
the offerer MUST in the SDP offer assign an SDP 'rtcp-mux' attribute
[RFC5761] to each bundled "m=" line (including any bundle-only "m="
line). In addition, the offerer MUST in the SDP offer assign an SDP
'rtcp' attribute [RFC3605] to each bundled "m=" line (including any
bundle-only "m=" line), with an attribute value that is identical to
the port value assigned to the "m=" line itself.
If the offerer does not want to negotiate usage of RTP/RTCP
multiplexing, the offerer MUST NOT assign the SDP attributes above to
any bundled "m=" line.
8.3.2.3. Generating the Answer
8.3.2.3.1. Generating the Answer to an Initial Offer
When the answerer generates an SDP answer to an initial SDP offer, if
the offerer in the associated SDP offer indicated support of RTP/RTCP
multiplexing [RFC5761] within a BUNDLE group, the answerer MUST in
the SDP answer either accept or reject usage of RTP/RTCP
multiplexing.
If the answerer accepts usage of RTP/RTCP multiplexing within the
BUNDLE group, the answerer MUST in the SDP answer assign an SDP
'rtcp-mux' attribute to each bundled "m=" line. The answerer MUST
NOT in the SDP answer assign an SDP 'rtcp' attribute to any bundled
"m=" line.
OPEN ISSUE: Do we want to include the SDP 'rtcp' attribute also in
the SDP answer, eventhough it is not needed?
If the answerer rejects usage of RTP/RTCP multiplexing within the
BUNDLE group, the answerer MUST NOT in the SDP answer assign an SDP
'rtcp-mux' or SDP 'rtcp' attribute to any bundled "m=" line.
8.3.2.3.2. Generating the Answer to a Subsequent Offer
When the answerer generates an SDP answer to a subsequent SDP offer,
if the offerer in the associated SDP offer indicated support of RTP/
RTCP multiplexing [RFC5761] within a BUNDLE group, the answerer MUST
in the SDP answer assign an SDP 'rtcp-mux' attribute and SDP 'rtcp'
attribute to each bundled "m=" line.
NOTE: The BUNDLE mechanism does not allow the answerer to, in a
subsequent SDP answer, disable usage of RTP/RTCP multiplexing, if the
offerer in the associated SDP offer indicates that it wants to
continue using RTP/RTCP multiplexing.
8.3.2.4. Offerer Processing of the Answer
When the offerer receives an SDP answer, it follows the procedures
defined in [RFC5245].
8.3.2.5. Modifying the Session
When an offerer generates a subsequent SDP offer, if the offerer
wants to negotiate usage of RTP/RTCP multiplexing within a BUNDLE
group, or if the offerer wants to continue usage of previously
negotiated RTP/RTCP multiplexing within the BUNDLE group, the offerer
MUST in the SDP offer assign 'rtcp-mux' and 'rtcp' attributes to each
bundled "m=" line (including bundle-only "m=" lines), unless the "m="
line is disabled or removed from the BUNDLE group.
If the offerer does not want to negotiate usage of RTP/RTCP
multiplexing within the BUNDLE group, or if the offerer wants to
disable previously negotiated usage of RTP/RTCP multiplexing within a
BUNDLE group, the offerer MUST NOT in the SDP offer assign 'rtcp-mux'
and 'rtcp' attributes to any bundled "m=" line.
NOTE: It is RECOMMENDED that, once usage of RTP/RTCP multiplexing has
been negotiated within a BUNDLE group, that the usage of not
disabled. Disabling RTP/RTCP multiplexing means that the offerer and
answerer need to reserve new IP ports, to be used for sending and
receiving RTCP packets.
9. ICE Considerations
9.1. General
This section describes how to use the BUNDLE grouping extension This section describes how to use the BUNDLE grouping extension
together with the Interactive Connectivity Establishment (ICE) together with the Interactive Connectivity Establishment (ICE)
mechanism [RFC5245]. mechanism [RFC5245].
8.2. Candidates Support and usage of ICE mechanism together with the BUNDLE mechanism
is optional.
When an ICE-enabled endpoint generates an SDP Offer, which contains a 9.2. SDP Offer/Answer Procedures
BUNDLE group, the SDP Offerer MUST include ICE candidates for each
"m=" line associated with a "BUNDLE" group, except for any "m=" line
with a zero port number value. If the "m=" lines associated with the
BUNDLE group contain different port number values, the SDP Offerer
MUST also insert different candidate values in each "m=" line
associated with the BUNDLE group. If the "m=" lines associated with
the BUNDLE group contain an identical port number value, the
candidate values MUST also be identical.
When an ICE-enabled endpoint generates and SDP Answer, which contains 9.2.1. Generating the Initial Offer
a BUNDLE group, the Answerer MUST include ICE candidates for each
"m=" line associated with the "BUNDLE" group, except for any "m="
line where the port number value is set to zero. The Answerer MUST
insert identical candidate values in each "m=" line associated with
the BUNDLE group.
8.3. Candidates When an offerer generates an initial SDP offer, which contains a
BUNDLE group, the offerer MUST assign ICE candidates [RFC5245] to
each bundled "m=" line, except to an "m=" line to which the offerer
assigns a zero port value (e.g. a bundle-only "m=" line). The
offerer MUST assign unique ICE candidate values to each "m=" line.
9.2.2. Generating the Answer
When an answerer generates and SDP Answer, which contains a BUNDLE
group, the answerer MUST assign ICE candidates to each bundled "m="
line. The answerer MUST assign identical ICE candidate values to
each bundled "m=" line.
9.2.3. Offerer Processing of the Answer
When the offerer receives an SDP answer, it follows the procedures
defined in [RFC5245].
9.2.4. Modifying the Session
When an offerer generates a subsequent SDP offer, for each bundled
"m=" line to which the offerer assigns its BUNDLE address, the
offerer MUST assign identical ICE candidate values. The offerer MUST
assign the ICE candidate values associated with the "m=" line that
was used by the answerer to select the offerer BUNDLE address [ref-
to-be-added].
9.2.5. Keep-alives
Once it is known that both endpoints support, and accept to use, the Once it is known that both endpoints support, and accept to use, the
BUNDLE grouping extension, ICE connectivity checks and keep-alives BUNDLE grouping extension, ICE connectivity checks and keep-alives
only needs to be performed for the whole BUNDLE group, instead of for only needs to be performed for the whole BUNDLE group, instead of for
each individual "m=" line associated with the group. each bundled "m=" line.
10. Update to RFC 3264
10.1. General
This section replaces the text of the following sections of RFC 3264:
o Section 5.1 (Unicast Streams).
o Section 8.2 (Removing a Media Stream).
o Section 8.4 (Putting a Unicast Media Stream on Hold).
10.2. Original text of section 5.1 (2nd paragraph) of RFC 3264
For recvonly and sendrecv streams, the port number and address in the
offer indicate where the offerer would like to receive the media
stream. For sendonly RTP streams, the address and port number
indirectly indicate where the offerer wants to receive RTCP reports.
Unless there is an explicit indication otherwise, reports are sent to
the port number one higher than the number indicated. The IP address
and port present in the offer indicate nothing about the source IP
address and source port of RTP and RTCP packets that will be sent by
the offerer. A port number of zero in the offer indicates that the
stream is offered but MUST NOT be used. This has no useful semantics
in an initial offer, but is allowed for reasons of completeness,
since the answer can contain a zero port indicating a rejected stream
(Section 6). Furthermore, existing streams can be terminated by
setting the port to zero (Section 8). In general, a port number of
zero indicates that the media stream is not wanted.
10.3. New text replacing section 5.1 (2nd paragraph) of RFC 3264
For recvonly and sendrecv streams, the port number and address in the
offer indicate where the offerer would like to receive the media
stream. For sendonly RTP streams, the address and port number
indirectly indicate where the offerer wants to receive RTCP reports.
Unless there is an explicit indication otherwise, reports are sent to
the port number one higher than the number indicated. The IP address
and port present in the offer indicate nothing about the source IP
address and source port of RTP and RTCP packets that will be sent by
the offerer. A port number of zero in the offer by default indicates
that the stream is offered but MUST NOT be used, but an extension
mechanism might specify different semantics for the usage of a zero
port value. Furthermore, existing streams can be terminated by
setting the port to zero (Section 8). In general, a port number of
zero by default indicates that the media stream is not wanted.
10.4. Original text of section 8.2 (2nd paragraph) of RFC 3264
A stream that is offered with a port of zero MUST be marked with port
zero in the answer. Like the offer, the answer MAY omit all
attributes present previously, and MAY list just a single media
format from amongst those in the offer.
10.5. New text replacing section 8.2 (2nd paragraph) of RFC 3264
A stream that is offered with a port of zero MUST by default be
marked with port zero in the answer, unless an extension mechanism,
which specifies semantics for the usage of a non-zero port value, is
used.
10.6. Original text of section 8.4 (6th paragraph) of RFC 3264
RFC 2543 [10] specified that placing a user on hold was accomplished
by setting the connection address to 0.0.0.0. Its usage for putting
a call on hold is no longer recommended, since it doesn't allow for
RTCP to be used with held streams, doesn't work with IPv6, and breaks
with connection oriented media. However, it can be useful in an
initial offer when the offerer knows it wants to use a particular set
of media streams and formats, but doesn't know the addresses and
ports at the time of the offer. Of course, when used, the port
number MUST NOT be zero, which would specify that the stream has been
disabled. An agent MUST be capable of receiving SDP with a
connection address of 0.0.0.0, in which case it means that neither
RTP nor RTCP should be sent to the peer.
10.7. New text replacing section 8.4 (6th paragraph) of RFC 3264
RFC 2543 [10] specified that placing a user on hold was accomplished
by setting the connection address to 0.0.0.0. Its usage for putting
a call on hold is no longer recommended, since it doesn't allow for
RTCP to be used with held streams, doesn't work with IPv6, and breaks
with connection oriented media. However, it can be useful in an
initial offer when the offerer knows it wants to use a particular set
of media streams and formats, but doesn't know the addresses and
ports at the time of the offer. Of course, when used, the port
number MUST NOT be zero, if it would specify that the stream has been
disabled. However, an extension mechanism might specify different
semantics of the zero port number usage. An agent MUST be capable of
receiving SDP with a connection address of 0.0.0.0, in which case it
means that neither RTP nor RTCP should be sent to the peer.
11. Security Considerations
9. Security Considerations
This specification does not significantly change the security This specification does not significantly change the security
considerations of SDP which can be found in Section X of TBD. considerations of SDP which can be found in Section X of TBD.
TODO: Think carefully about security analysis of reuse of same SDES TODO: Think carefully about security analysis of reuse of same SDES
key on multiple "m=" lines when the far end does not use BUNDLE and key on multiple "m=" lines when the far end does not use BUNDLE and
warn developers of any risks. warn developers of any risks.
10. Examples 12. Examples
10.1. Example: Bundle Address Selection 12.1. Example: Bundle Address Selection
The example below shows: The example below shows:
o 1. An SDP Offer, in which the Offerer assigns unique addresses to o 1. An SDP offer, in which the offerer assigns a unique address to
each "m=" line in the BUNDLE group, and requests the Answerer to each bundled "m=" line within the BUNDLE group.
select the Offerer's BUNDLE address.
o 2. An SDP Answer, in which the Answerer selects the BUNDLE o 2. An SDP answer, in which the answerer selects the offerer
address for the Offerer, and assigns its own local BUNDLE address BUNDLE address, and in which selects its own BUNDLE address (the
to each "m=" line in the BUNDLE group. answerer BUNDLE address) and assigns it each bundled "m=" line
within the BUNDLE group.
o 3. A subsequent SDP Offer, which is used to perform a Bundle o 3. A subsequent SDP offer (BAS offer), which is used to perform a
Address Synchronization (BAS). Bundle Address Synchronization (BAS).
SDP Offer (1) SDP Offer (1)
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
skipping to change at page 14, line 39 skipping to change at page 24, line 25
b=AS:200 b=AS:200
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000 a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000 a=rtpmap:97 iLBC/8000
m=video 10000 RTP/AVP 31 32 m=video 10000 RTP/AVP 31 32
a=mid:bar a=mid:bar
b=AS:1000 b=AS:1000
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
10.2. Example: Bundle Mechanism Rejected 12.2. Example: Bundle Mechanism Rejected
The example below shows: The example below shows:
o 1. An SDP Offer, in which the Offerer assigns unique addresses to o 1. An SDP offer, in which the offerer assigns a unique address to
each "m=" line in the BUNDLE group, and requests the Answerer to each bundled "m=" line within the BUNDLE group.
select the Offerer's BUNDLE address.
o 2. An SDP Answer, in which the Answerer rejects the BUNDLE group, o 2. An SDP answer, in which the answerer rejects the offered
and assigns unique addresses to each "m=" line. BUNDLE group, and assigns a unique addresses to each "m=" line
(following normal RFC 3264 procedures).
SDP Offer (1) SDP Offer (1)
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
skipping to change at page 15, line 39 skipping to change at page 25, line 39
s= s=
c=IN IP4 biloxi.example.com c=IN IP4 biloxi.example.com
t=0 0 t=0 0
m=audio 20000 RTP/AVP 0 m=audio 20000 RTP/AVP 0
b=AS:200 b=AS:200
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
m=video 30000 RTP/AVP 32 m=video 30000 RTP/AVP 32
b=AS:1000 b=AS:1000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
10.3. Example: Offerer Adds A Media Description To A BUNDLE Group 12.3. Example: Offerer Adds A Media Description To A BUNDLE Group
The example below shows: The example below shows:
o 1. An SDP Offer, in which the Offerer adds an "m=" line, o 1. An SDP offer, in which the offerer adds a new "m=" line,
represented by the "zen" mid value, to a previously negotiated represented by the "zen" mid value, to a previously negotiated
BUNDLE group, assigns a unique address to the added "m=" line, and BUNDLE group, assigns a unique address to the added "m=" line, and
assigns the previously negotiated BUNDLE address to the previously assigns the previously selected offerer BUNDLE address to each of
added "m=" lines in the BUNDLE group. the other bundled "m=" lines within the BUNDLE group.
o 2. An SDP Answer, in which the Answerer assigns its own local o 2. An SDP answer, in which the answerer assigns the answerer
BUNDLE address to each "m=" line (including the added "m=" line) BUNDLE address to each bundled "m=" line (including the newly
in the BUNDLE group. added "m=" line) within the BUNDLE group.
o 3. A subsequent SDP Offer, which is used to perform a Bundle o 3. A subsequent SDP offer (BAS offer), which is used to perform a
Address Synchronization (BAS). Bundle Address Synchronization (BAS).
SDP Offer (1) SDP Offer (1)
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar zen a=group:BUNDLE foo bar zen
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
skipping to change at page 17, line 34 skipping to change at page 27, line 34
m=video 10000 RTP/AVP 31 32 m=video 10000 RTP/AVP 31 32
a=mid:bar a=mid:bar
b=AS:1000 b=AS:1000
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
m=video 10000 RTP/AVP 66 m=video 10000 RTP/AVP 66
a=mid:zen a=mid:zen
b=AS:1000 b=AS:1000
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
10.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group 12.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group
The example below shows: The example below shows:
o 1. An SDP Offer, in which the Offerer moves an "m=" line out of a o 1. An SDP offer, in which the offerer moves a bundled "m=" line
previously negotiated BUNDLE group, assigns a unique address to out of a BUNDLE group, assigns a unique address to the moved "m="
the moved "m=" line, and assigns the previously negotiated BUNDLE line, and assigns the offerer BUNDLE address to each other bundled
address to the remaining "m=" lines in the BUNDLE group. "m=" line within the BUNDLE group.
o 2. An SDP Answer, in which the Answerer moves the corresponding o 2. An SDP answer, in which the answerer moves the "m=" line out
"m=" line out of the BUNDLE group, and assigns unique address to of the BUNDLE group, assigns unique address to the moved "m="
the moved "m=" line, and assigns the previously negotiated BUNDLE line, and assigns the answerer BUNDLE address to each other
address to the remaining "m=" lines in the BUNDLE group. bundled "m=" line within the BUNDLE group.
SDP Offer (1) SDP Offer (1)
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
skipping to change at page 19, line 5 skipping to change at page 29, line 5
b=AS:200 b=AS:200
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
a=mid:bar a=mid:bar
b=AS:1000 b=AS:1000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
m=video 60000 RTP/AVP 66 m=video 60000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
10.5. Example: Offerer Disables A Media Description In A BUNDLE Group 12.5. Example: Offerer Disables A Media Description Within A BUNDLE
Group
The example below shows: The example below shows:
o 1. An SDP Offer, in which the Offerer moves an "m=" line out of a o 1. An SDP offer, in which the offerer disables a bundled "m="
previously negotiated BUNDLE group, assigns a zero port number the line within BUNDLE group, assigns a zero port number the disabled
moved "m=" line in order to disable it, and assigns the previously "m=" line, and assigns the offerer BUNDLE address to each of the
negotiated BUNDLE address to the remaining "m=" lines in the other bundled "m=" lines within the BUNDLE group.
BUNDLE group.
o 2. An SDP Answer, in which the Answerer moves the corresponding o 2. An SDP answer, in which the answerer moves the disabled "m="
"m=" line out of the BUNDLE group, and assigns a zero port value line out of the BUNDLE group, assigns a zero port value to the
to the moved "m=" line in order to disable it, and assigns the disabled "m=" line, and assigns the answerer BUNDLE address to
previously negotiated BUNDLE address to the remaining "m=" lines each of the other bundled "m=" lines within the BUNDLE group.
in the BUNDLE group.
SDP Offer (1) SDP Offer (1)
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
skipping to change at page 20, line 15 skipping to change at page 31, line 5
a=mid:foo a=mid:foo
b=AS:200 b=AS:200
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
a=mid:bar a=mid:bar
b=AS:1000 b=AS:1000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
m=video 0 RTP/AVP 66 m=video 0 RTP/AVP 66
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
11. IANA Considerations 13. IANA Considerations
This document requests IANA to register the new SDP Grouping semantic This document requests IANA to register the new SDP Grouping semantic
extension called BUNDLE. extension called BUNDLE.
12. Acknowledgements 14. Acknowledgements
The usage of the SDP grouping extension for negotiating bundled media The usage of the SDP grouping extension for negotiating bundled media
is based on a similar alternatives proposed by Harald Alvestrand and is based on a similar alternatives proposed by Harald Alvestrand and
Cullen Jennings. The BUNDLE mechanism described in this document is Cullen Jennings. The BUNDLE mechanism described in this document is
based on the different alternative proposals, and text (e.g. SDP based on the different alternative proposals, and text (e.g. SDP
examples) have been borrowed (and, in some cases, modified) from examples) have been borrowed (and, in some cases, modified) from
those alternative proposals. those alternative proposals.
The SDP examples are also modified versions from the ones in the The SDP examples are also modified versions from the ones in the
Alvestrand proposal. Alvestrand proposal.
Thanks to Paul Kyzivat and Martin Thompson for taking the the time to Thanks to Paul Kyzivat and Martin Thompson for taking the the time to
read the text along the way, and providing useful feedback. read the text along the way, and providing useful feedback.
13. Change Log 15. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing] [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-05
o Major re-structure of SDP Offer/Answer sections, to align with RFC
3264 structure.
o Additional definitions added.
o - Shared address.
o - Bundled "m=" line.
o - Bundle-only "m=" line.
o - Offerer suggested BUNDLE mid.
o - Answerer selected BUNDLE mid.
o Q6 Closed (IETF#88): An Offerer MUST NOT assign a shared address
to multiple "m=" lines until it has received an SDP Answer
indicating support of the BUNDLE mechanism.
o Q8 Closed (IETF#88): An Offerer can, before it knows whether the
Answerer supports the BUNDLE mechanism, assign a zero port value
to a 'bundle-only' "m=" line.
o SDP 'bundle-only' attribute section added.
o Connection data nettype/addrtype restrictions added.
o RFC 3264 update section added.
o Indicating that a specific payload type value can be used in
multiple "m=" lines, if the value represents the same codec
configuration in each "m=" line.
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-04 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-04
o Updated Offerer procedures (http://www.ietf.org/mail-archive/web/ o Updated Offerer procedures (http://www.ietf.org/mail-archive/web/
mmusic/current/msg12293.html). mmusic/current/msg12293.html).
o Updated Answerer procedures (http://www.ietf.org/mail-archive/web/ o Updated Answerer procedures (http://www.ietf.org/mail-archive/web/
mmusic/current/msg12333.html). mmusic/current/msg12333.html).
o Usage of SDP 'bundle-only' attribute added. o Usage of SDP 'bundle-only' attribute added.
skipping to change at page 21, line 35 skipping to change at page 33, line 7
o Draft name changed. o Draft name changed.
o Harald Alvestrand added as co-author. o Harald Alvestrand added as co-author.
o "Multiplex" terminology changed to "bundle". o "Multiplex" terminology changed to "bundle".
o Added text about single versus multiple RTP Sessions. o Added text about single versus multiple RTP Sessions.
o Added reference to RFC 3550. o Added reference to RFC 3550.
14. References 16. References
14.1. Normative References 16.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June with Session Description Protocol (SDP)", RFC 3264, June
2002. 2002.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, April 2010. Control Packets on a Single Port", RFC 5761, April 2010.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010. Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
[I-D.nandakumar-mmusic-sdp-mux-attributes] [I-D.nandakumar-mmusic-sdp-mux-attributes]
Nandakumar, S. and C. Jennings, "A Framework for SDP Nandakumar, S., "A Framework for SDP Attributes when
Attributes when Multiplexing ", draft-nandakumar-mmusic- Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-01
sdp-mux-attributes-04 (work in progress), September 2013. (work in progress), February 2014.
14.2. Informative References 16.2. Informative References
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605, October in Session Description Protocol (SDP)", RFC 3605, October
2003. 2003.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, April Traversal for Offer/Answer Protocols", RFC 5245, April
2010. 2010.
[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, June 2009.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764, May 2010.
[I-D.ietf-mmusic-trickle-ice] [I-D.ietf-mmusic-trickle-ice]
Ivov, E., Rescorla, E., and J. Uberti, "Trickle ICE: Ivov, E., Rescorla, E., and J. Uberti, "Trickle ICE:
Incremental Provisioning of Candidates for the Interactive Incremental Provisioning of Candidates for the Interactive
Connectivity Establishment (ICE) Protocol ", draft-ietf- Connectivity Establishment (ICE) Protocol", draft-ietf-
mmusic-trickle-ice-00 (work in progress), October 2013. mmusic-trickle-ice-01 (work in progress), February 2014.
Appendix A. Design Considerations Appendix A. Design Considerations
A.1. General A.1. General
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 SDP Offers and SDP Answers, the same port number been whether, in SDP Offers and SDP Answers, the same port number
value should be inserted in "m=" lines associated with a BUNDLE value should be inserted in "m=" lines associated with a BUNDLE
group, as the purpose of the extension is to negotiate the usage of a group, as the purpose of the extension is to negotiate the usage of a
single 5-tuple for media associated with the "m=" lines. Issues with single 5-tuple for media associated with the "m=" lines. Issues with
 End of changes. 143 change blocks. 
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