draft-ietf-mmusic-sdp-bundle-negotiation-31.txt   draft-ietf-mmusic-sdp-bundle-negotiation-32.txt 
MMUSIC Working Group C. Holmberg MMUSIC Working Group C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Updates: 3264 (if approved) H. Alvestrand Updates: 3264 (if approved) H. Alvestrand
Intended status: Standards Track Google Intended status: Standards Track Google
Expires: December 21, 2016 C. Jennings Expires: February 18, 2017 C. Jennings
Cisco Cisco
June 19, 2016 August 17, 2016
Negotiating Media Multiplexing Using the Session Description Protocol Negotiating Media Multiplexing Using the Session Description Protocol
(SDP) (SDP)
draft-ietf-mmusic-sdp-bundle-negotiation-31.txt draft-ietf-mmusic-sdp-bundle-negotiation-32.txt
Abstract Abstract
This specification defines a new Session Description Protocol (SDP) This specification defines a new Session Description Protocol (SDP)
Grouping Framework extension, 'BUNDLE'. The extension can be used Grouping Framework extension, 'BUNDLE'. The extension can be used
with the SDP Offer/Answer mechanism to negotiate the usage of a with the SDP Offer/Answer mechanism to negotiate the usage of a
single address:port combination (BUNDLE address) for receiving media, single address:port combination (BUNDLE address) for receiving media,
referred to as bundled media, specified by multiple SDP media referred to as bundled media, specified by multiple SDP media
descriptions ("m=" lines). descriptions ("m=" lines).
To assist endpoints in negotiating the use of bundle this To assist endpoints in negotiating the use of bundle this
specification defines a new SDP attribute, 'bundle-only', which can specification defines a new SDP attribute, 'bundle-only', which can
be used to request that specific media is only used if bundled. The be used to request that specific media is only used if bundled. The
specification also updates RFC 3264, to allow usage of zero port specification also updates RFC 3264, to allow usage of zero port
values without meaning that media is rejcted. values without meaning that media is rejected.
There are multiple ways to correlate the bundled RTP packets with the There are multiple ways to correlate the bundled RTP packets with the
appropriate media descriptions. This specification defines a new appropriate media descriptions. This specification defines a new
Real-time Transport Protocol (RTP) source description (SDES) item and Real-time Transport Protocol (RTP) source description (SDES) item and
a new RTP header extension that provides an additional way to do this a new RTP header extension that provides an additional way to do this
correlation by using them to carry a value that associates the RTP/ correlation by using them to carry a value that associates the RTP/
RTCP packets with a specific media description. RTCP packets with a specific media description.
Status of This Memo Status of This Memo
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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 December 21, 2016. This Internet-Draft will expire on February 18, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
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 . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 7 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 7
5. SDP Grouping Framework BUNDLE Extension . . . . . . . . . . . 7 5. SDP Grouping Framework BUNDLE Extension . . . . . . . . . . . 7
6. SDP 'bundle-only' Attribute . . . . . . . . . . . . . . . . . 8 6. SDP 'bundle-only' Attribute . . . . . . . . . . . . . . . . . 8
7. SDP Information Considerations . . . . . . . . . . . . . . . 9 7. SDP Information Considerations . . . . . . . . . . . . . . . 8
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Connection Data (c=) . . . . . . . . . . . . . . . . . . 9
7.2. Connection Data (c=) . . . . . . . . . . . . . . . . . . 9 7.2. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . . . 9
7.3. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . . . 9 7.3. Attributes (a=) . . . . . . . . . . . . . . . . . . . . . 9
7.4. Attributes (a=) . . . . . . . . . . . . . . . . . . . . . 9
8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 9 8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 9
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Mux Category Considerations . . . . . . . . . . . . . . . 10
8.2. Mux Category Considerations . . . . . . . . . . . . . . . 10 8.2. Generating the Initial SDP Offer . . . . . . . . . . . . 10
8.3. Generating the Initial SDP Offer . . . . . . . . . . . . 10 8.2.1. Suggesting the offerer BUNDLE address . . . . . . . . 11
8.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 11
8.3.2. Suggesting the offerer BUNDLE address . . . . . . . . 11 8.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 11
8.4. Generating the SDP Answer . . . . . . . . . . . . . . . . 11 8.3.1. Answerer Selection of Offerer Bundle Address . . . . 12
8.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 12 8.3.2. Answerer Selection of Answerer BUNDLE Address . . . . 13
8.4.2. Answerer Selection of Offerer Bundle Address . . . . 13 8.3.3. Moving A Media Description Out Of A BUNDLE Group . . 13
8.4.3. Answerer Selection of Answerer BUNDLE Address . . . . 13 8.3.4. Rejecting A Media Description In A BUNDLE Group . . . 14
8.4.4. Moving A Media Description Out Of A BUNDLE Group . . 14 8.4. Offerer Processing of the SDP Answer . . . . . . . . . . 14
8.4.5. Rejecting A Media Description In A BUNDLE Group . . . 14 8.5. Modifying the Session . . . . . . . . . . . . . . . . . . 14
8.5. Offerer Processing of the SDP Answer . . . . . . . . . . 14 8.5.1. Suggesting a new offerer BUNDLE address . . . . . . . 15
8.6. Modifying the Session . . . . . . . . . . . . . . . . . . 15 8.5.2. Adding a media description to a BUNDLE group . . . . 15
8.6.1. General . . . . . . . . . . . . . . . . . . . . . . . 15 8.5.3. Moving A Media Description Out Of A BUNDLE Group . . 16
8.6.2. Suggesting a new offerer BUNDLE address . . . . . . . 15 8.5.4. Disabling A Media Description In A BUNDLE Group . . . 16
8.6.3. Adding a media description to a BUNDLE group . . . . 16
8.6.4. Moving A Media Description Out Of A BUNDLE Group . . 16
8.6.5. Disabling A Media Description In A BUNDLE Group . . . 17
9. Protocol Identification . . . . . . . . . . . . . . . . . . . 17 9. Protocol Identification . . . . . . . . . . . . . . . . . . . 17
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17 9.1. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 17
9.2. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 18
10. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 18 10. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 18
10.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 18 10.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 18
10.1.1. General . . . . . . . . . . . . . . . . . . . . . . 18 10.1.1. Payload Type (PT) Value Reuse . . . . . . . . . . . 18
10.1.2. Payload Type (PT) Value Reuse . . . . . . . . . . . 19
10.2. Associating RTP/RTCP Packets With Correct SDP Media 10.2. Associating RTP/RTCP Packets With Correct SDP Media
Description . . . . . . . . . . . . . . . . . . . . . . 19 Description . . . . . . . . . . . . . . . . . . . . . . 19
10.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . 20 10.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . 20
10.3.1. General . . . . . . . . . . . . . . . . . . . . . . 20 10.3.1. SDP Offer/Answer Procedures . . . . . . . . . . . . 20
10.3.2. SDP Offer/Answer Procedures . . . . . . . . . . . . 20
11. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 22 11. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 22
11.1. General . . . . . . . . . . . . . . . . . . . . . . . . 23 11.1. SDP Offer/Answer Procedures . . . . . . . . . . . . . . 22
11.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . . 23 11.1.1. Generating the Initial SDP Offer . . . . . . . . . . 23
11.2.1. General . . . . . . . . . . . . . . . . . . . . . . 23 11.1.2. Generating the SDP Answer . . . . . . . . . . . . . 23
11.2.2. Generating the Initial SDP Offer . . . . . . . . . . 24 11.1.3. Offerer Processing of the SDP Answer . . . . . . . . 24
11.2.3. Generating the SDP Answer . . . . . . . . . . . . . 24 11.1.4. Modifying the Session . . . . . . . . . . . . . . . 24
11.2.4. Offerer Processing of the SDP Answer . . . . . . . . 24 12. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 24
11.2.5. Modifying the Session . . . . . . . . . . . . . . . 24
12. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 25
13. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 25 13. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 25
13.1. General . . . . . . . . . . . . . . . . . . . . . . . . 25 13.1. Original text of section 5.1 (2nd paragraph) of RFC 3264 25
13.2. Original text of section 5.1 (2nd paragraph) of RFC 3264 26 13.2. New text replacing section 5.1 (2nd paragraph) of RFC
13.3. New text replacing section 5.1 (2nd paragraph) of RFC 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 25
13.3. Original text of section 8.2 (2nd paragraph) of RFC 3264 26
13.4. New text replacing section 8.2 (2nd paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.4. Original text of section 8.2 (2nd paragraph) of RFC 3264 26 13.5. Original text of section 8.4 (6th paragraph) of RFC 3264 26
13.5. New text replacing section 8.2 (2nd paragraph) of RFC 13.6. New text replacing section 8.4 (6th paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.6. Original text of section 8.4 (6th paragraph) of RFC 3264 27
13.7. New text replacing section 8.4 (6th paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 27
14. RTP/RTCP extensions for identification-tag transport . . . . 27 14. RTP/RTCP extensions for identification-tag transport . . . . 27
14.1. General . . . . . . . . . . . . . . . . . . . . . . . . 27 14.1. RTCP MID SDES Item . . . . . . . . . . . . . . . . . . . 28
14.2. RTCP MID SDES Item . . . . . . . . . . . . . . . . . . . 28 14.2. RTP SDES Header Extension For MID . . . . . . . . . . . 28
14.3. RTP MID Header Extension . . . . . . . . . . . . . . . . 29
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
15.1. New SDES item . . . . . . . . . . . . . . . . . . . . . 29 15.1. New SDES item . . . . . . . . . . . . . . . . . . . . . 29
15.2. New RTP Header Extension URI . . . . . . . . . . . . . . 30 15.2. New RTP SDES Header Extension URI . . . . . . . . . . . 29
15.3. New SDP Attribute . . . . . . . . . . . . . . . . . . . 30 15.3. New SDP Attribute . . . . . . . . . . . . . . . . . . . 30
15.4. New SDP Group Semantics . . . . . . . . . . . . . . . . 31 15.4. New SDP Group Semantics . . . . . . . . . . . . . . . . 30
16. Security Considerations . . . . . . . . . . . . . . . . . . . 31 16. Security Considerations . . . . . . . . . . . . . . . . . . . 31
17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 32 17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 31
17.1. Example: Bundle Address Selection . . . . . . . . . . . 32 17.1. Example: Bundle Address Selection . . . . . . . . . . . 31
17.2. Example: BUNDLE Extension Rejected . . . . . . . . . . . 34 17.2. Example: BUNDLE Extension Rejected . . . . . . . . . . . 33
17.3. Example: Offerer Adds A Media Description To A BUNDLE 17.3. Example: Offerer Adds A Media Description To A BUNDLE
Group . . . . . . . . . . . . . . . . . . . . . . . . . 35 Group . . . . . . . . . . . . . . . . . . . . . . . . . 34
17.4. Example: Offerer Moves A Media Description Out Of A 17.4. Example: Offerer Moves A Media Description Out Of A
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 37 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 36
17.5. Example: Offerer Disables A Media Description Within A 17.5. Example: Offerer Disables A Media Description Within A
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 38 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 38
18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 40 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39
19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 40 19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 40
20. References . . . . . . . . . . . . . . . . . . . . . . . . . 47 20. References . . . . . . . . . . . . . . . . . . . . . . . . . 47
20.1. Normative References . . . . . . . . . . . . . . . . . . 47 20.1. Normative References . . . . . . . . . . . . . . . . . . 47
20.2. Informative References . . . . . . . . . . . . . . . . . 49 20.2. Informative References . . . . . . . . . . . . . . . . . 49
Appendix A. Design Considerations . . . . . . . . . . . . . . . 50 Appendix A. Design Considerations . . . . . . . . . . . . . . . 50
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 50 A.1. UA Interoperability . . . . . . . . . . . . . . . . . . . 50
A.2. UA Interoperability . . . . . . . . . . . . . . . . . . . 50 A.2. Usage of port number value zero . . . . . . . . . . . . . 52
A.3. Usage of port number value zero . . . . . . . . . . . . . 52 A.3. B2BUA And Proxy Interoperability . . . . . . . . . . . . 52
A.4. B2BUA And Proxy Interoperability . . . . . . . . . . . . 52 A.3.1. Traffic Policing . . . . . . . . . . . . . . . . . . 53
A.4.1. Traffic Policing . . . . . . . . . . . . . . . . . . 53 A.3.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 53
A.4.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 53 A.4. Candidate Gathering . . . . . . . . . . . . . . . . . . . 53
A.5. Candidate Gathering . . . . . . . . . . . . . . . . . . . 53
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
1. Introduction 1. Introduction
This specification defines a way to use a single address:port This specification defines a way to use a single address:port
combination (BUNDLE address) for receiving media specified by combination (BUNDLE address) for receiving media specified by
multiple SDP media descriptions ("m=" lines). multiple SDP media descriptions ("m=" lines).
This specification defines a new SDP Grouping Framework [RFC5888] This specification defines a new SDP Grouping Framework [RFC5888]
extension called 'BUNDLE'. The extension can be used with the extension called 'BUNDLE'. The extension can be used with the
skipping to change at page 5, line 22 skipping to change at page 5, line 9
specified by the BUNDLE group. specified by the BUNDLE group.
The use of a BUNDLE group and a BUNDLE address also allows the usage The use of a BUNDLE group and a BUNDLE address also allows the usage
of a single set of Interactive Connectivity Establishment (ICE) of a single set of Interactive Connectivity Establishment (ICE)
[RFC5245] candidates for multiple "m=" lines. [RFC5245] candidates for multiple "m=" lines.
This specification also defines a new SDP attribute, 'bundle-only', This specification also defines a new SDP attribute, 'bundle-only',
which can be used to request that specific media is only used if kept which can be used to request that specific media is only used if kept
within a BUNDLE group. The specification also updates RFC 3264, to within a BUNDLE group. The specification also updates RFC 3264, to
allow usage of zero port values without meaning that media is allow usage of zero port values without meaning that media is
rejcted. rejected.
As defined in RFC 4566 [RFC4566], the semantics of assigning the same As defined in RFC 4566 [RFC4566], the semantics of assigning the same
port value to multiple "m=" lines are undefined, and there is no transport address (IP address and port) to multiple "m=" lines are
grouping defined by such means. Instead, an explicit grouping undefined, and there is no grouping defined by such means. Instead,
mechanism needs to be used to express the intended semantics. This an explicit grouping mechanism needs to be used to express the
specification provides such an extension. intended semantics. This specification provides such an extension.
This specification also updates sections 5.1, 8.1 and 8.2 of RFC 3264 This specification also updates sections 5.1, 8.1 and 8.2 of RFC 3264
[RFC3264]. The update allows an answerer to assign a non-zero port [RFC3264]. The update allows an answerer to assign a non-zero port
value to an "m=" line in an SDP answer, even if the "m=" line in the value to an "m=" line in an SDP answer, even if the "m=" line in the
associated SDP offer contained a zero port value. associated SDP offer contained a zero port value.
This specification also defines a new Real-time Transport Protocol This specification also defines a new Real-time Transport Protocol
(RTP) [RFC3550] source description (SDES) item and a new RTP header (RTP) [RFC3550] source description (SDES) item and a new RTP header
extension that can be used to carry a value that associates RTP/RTCP extension that can be used to carry a value that associates RTP/RTCP
packets with a specific media description. This can be used to packets with a specific media description. This can be used to
skipping to change at page 8, line 24 skipping to change at page 8, line 21
Name: bundle-only Name: bundle-only
Value: N/A Value: N/A
Usage Level: media Usage Level: media
Charset Dependent: no Charset Dependent: no
Example: Example:
a=bundle-only a=bundle-only
In order to ensure that an answerer that does not support the BUNDLE In order to ensure that an answerer that does not support the BUNDLE
extension always rejects a bundled "m=" line, the offerer can assign extension always rejects a bundled "m=" line, the offerer can assign
a zero port value to the "m=" line. According to [RFC4566] an a zero port value to the "m=" line. According to [RFC3264] an
answerer will reject such "m=" line. By associating an SDP 'bundle- answerer will reject such "m=" line. By associating an SDP 'bundle-
only' attribute with such "m=" line, the offerer can request that the only' attribute with such "m=" line, the offerer can request that the
answerer accepts the "m=" line if the answerer supports the Bundle answerer accepts the "m=" line if the answerer supports the Bundle
extension, and if the answerer keeps the "m=" line within the extension, and if the answerer keeps the "m=" line within the
associated BUNDLE group. associated BUNDLE group.
NOTE: Once the offerer BUNDLE address has been selected, the offerer NOTE: Once the offerer BUNDLE address has been selected, the offerer
does not need to include the 'bundle-only' attribute in subsequent does not need to include the 'bundle-only' attribute in subsequent
offers. By associating the offerer BUNDLE address with an "m=" line offers. By associating the offerer BUNDLE address with an "m=" line
of a subsequent offer, the offerer will ensure that the answerer will of a subsequent offer, the offerer will ensure that the answerer will
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The usage of the 'bundle-only' attribute is only defined for a The usage of the 'bundle-only' attribute is only defined for a
bundled "m=" line with a zero port value, within an offer. Other bundled "m=" line with a zero port value, within an offer. Other
usage is unspecified. usage is unspecified.
Section 8 defines the detailed SDP Offer/Answer procedures for the Section 8 defines the detailed SDP Offer/Answer procedures for the
'bundle-only' attribute. 'bundle-only' attribute.
7. SDP Information Considerations 7. SDP Information Considerations
7.1. General
This section describes restrictions associated with the usage of SDP This section describes restrictions associated with the usage of SDP
parameters within a BUNDLE group. It also describes, when parameter parameters within a BUNDLE group. It also describes, when parameter
and attribute values have been associated with each bundled "m=" and attribute values have been associated with each bundled "m="
line, how to calculate a value for the whole BUNDLE group. line, how to calculate a value for the whole BUNDLE group.
7.2. Connection Data (c=) 7.1. Connection Data (c=)
The "c=" line nettype value [RFC4566] associated with a bundled "m=" The "c=" line nettype value [RFC4566] associated with a bundled "m="
line MUST be 'IN'. line MUST be 'IN'.
The "c=" line addrtype value [RFC4566] associated with a bundled "m=" The "c=" line addrtype value [RFC4566] associated with a bundled "m="
line MUST be 'IP4' or 'IP6'. The same value MUST be associated with line MUST be 'IP4' or 'IP6'. The same value MUST be associated with
each "m=" line. each "m=" line.
NOTE: Extensions to this specification can specify usage of the NOTE: Extensions to this specification can specify usage of the
BUNDLE mechanism for other nettype and addrtype values than the ones BUNDLE mechanism for other nettype and addrtype values than the ones
listed above. listed above.
7.3. Bandwidth (b=) 7.2. Bandwidth (b=)
An offerer and answerer MUST use the rules and restrictions defined An offerer and answerer MUST use the rules and restrictions defined
in [I-D.ietf-mmusic-sdp-mux-attributes] for when associating the SDP in [I-D.ietf-mmusic-sdp-mux-attributes] for associating the SDP
bandwidth (b=) line with bundled "m=" lines. bandwidth (b=) line with bundled "m=" lines.
7.4. Attributes (a=) 7.3. Attributes (a=)
An offerer and answerer MUST use the rules and restrictions defined An offerer and answerer MUST use the rules and restrictions defined
in [I-D.ietf-mmusic-sdp-mux-attributes] for when associating SDP in [I-D.ietf-mmusic-sdp-mux-attributes] for associating SDP
attributes with bundled "m=" lines. attributes with bundled "m=" lines.
8. SDP Offer/Answer Procedures 8. SDP Offer/Answer Procedures
8.1. General
This section describes the SDP Offer/Answer [RFC3264] procedures for: This section describes the SDP Offer/Answer [RFC3264] procedures for:
o Negotiating and creating of a BUNDLE group; and o Negotiating and creating a BUNDLE group; and
o Selecting the BUNDLE addresses (offerer BUNDLE address and o Selecting the BUNDLE addresses (offerer BUNDLE address and
answerer BUNDLE address); and answerer BUNDLE address); and
o Adding an "m=" line to a BUNDLE group; and o Adding an "m=" line to a BUNDLE group; and
o Moving an "m=" line out of a BUNDLE group; and o Moving an "m=" line out of a BUNDLE group; and
o Disabling an "m=" line within a BUNDLE group. o 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]
also apply to the BUNDLE extension. For example, if an offer is also apply to the BUNDLE extension. For example, if an offer is
rejected by the answerer, the previously negotiated SDP parameters rejected by the answerer, the previously negotiated SDP parameters
and characteristics (including those associated with a BUNDLE group) and characteristics (including those associated with a BUNDLE group)
apply. Hence, if an offerer generates an offer in which the offerer apply. Hence, if an offerer generates an offer in which the offerer
wants to create a BUNDLE group, and the answerer rejects the offer, wants to create a BUNDLE group, and the answerer rejects the offer,
the BUNDLE group is not created. the BUNDLE group is not created.
skipping to change at page 10, line 26 skipping to change at page 10, line 19
defines additional considerations for RTP based media. Section 6 defines additional considerations for RTP based media. Section 6
defines additional considerations for the usage of the SDP 'bundle- defines additional considerations for the usage of the SDP 'bundle-
only' attribute. Section 11 defines additional considerations for only' attribute. Section 11 defines additional considerations for
the usage of Interactive Connectivity Establishment (ICE) the usage of Interactive Connectivity Establishment (ICE)
[I-D.ietf-ice-rfc5245bis] mechanism. [I-D.ietf-ice-rfc5245bis] mechanism.
SDP offers and answers can contain multiple BUNDLE groups. The SDP offers and answers can contain multiple BUNDLE groups. The
procedures in this section apply independently to a given BUNDLE procedures in this section apply independently to a given BUNDLE
group. group.
8.2. Mux Category Considerations 8.1. Mux Category Considerations
When an offerer associates a shared address with a bundled "m=" line, When an offerer associates SDP attributes with a bundled "m=" line
the offerer shall associate IDENTICAL and TRANSPORT mux category SDP associated with a shared address, IDENTICAL and TRANSPORT mux
attributes [I-D.ietf-mmusic-sdp-mux-attributes] with the "m=" line category SDP attributes [I-D.ietf-mmusic-sdp-mux-attributes] are
only if the "m=" line is associated with the offerer BUNDLE-tag. associated with the "m=" line only if the "m=" line is also
Otherwise the offerer MUST NOT associate such SDP attributes with the associated with the offerer BUNDLE-tag. Otherwise the offerer MUST
"m=" line. NOT associate such SDP attributes with the "m=" line.
When an answerer associates a shared address with a bundled "m=" When an answerer associates SDP attributes with a bundled "m=" line,
line, the answerer shall associate IDENTICAL and TRANSPORT category IDENTICAL and TRANSPORT mux category SDP attributes are associated
SDP attributes with the "m=" line only if the "m=" line is associated with the "m=" line only if the "m=" line is also associated with the
with the answerer BUNDLE-tag. Otherwise the answerer MUST NOT answerer BUNDLE-tag. Otherwise the answerer MUST NOT associated such
associate such SDP attributes with the "m=" line. SDP attributes with the "m=" line.
NOTE: As bundled "m=" lines associated with a shared address will NOTE: As bundled "m=" lines associated with a shared address will
share the same IDENTICAL and TRANSPORT mux category SDP attributes, share the same IDENTICAL and TRANSPORT mux category SDP attributes,
and attribute values, there is no need to associate such SDP and attribute values, there is no need to associate such SDP
attributes with each "m=" line. attributes with each "m=" line. The attributes and attribute values
are implicitly applied to each "m=" line associated with the shared
address.
8.3. Generating the Initial SDP Offer 8.2. Generating the Initial SDP Offer
8.3.1. General
When an offerer generates an initial offer, in order to create a When an offerer generates an initial offer, in order to create a
BUNDLE group, it MUST: BUNDLE group, it MUST:
o Assign a unique address to each "m=" line within the offer, o Assign a unique address to each "m=" line within the offer,
following the procedures in [RFC3264], unless the media line is a following the procedures in [RFC3264], unless the media line is a
'bundle-only' "m=" line (see below); and 'bundle-only' "m=" line (see below); and
o Add an SDP 'group:BUNDLE' attribute to the offer; and o Add an SDP 'group:BUNDLE' attribute to the offer; and
o Place the identification-tag of each bundled "m=" line in the SDP o Place the identification-tag of each bundled "m=" line in the SDP
'group:BUNDLE' attribute identification-tag list; and 'group:BUNDLE' attribute identification-tag list; and
o Indicate which unique address the offerer suggests as the offerer o Indicate which unique address the offerer suggests as the offerer
BUNDLE address [Section 8.3.2]. BUNDLE address [Section 8.2.1].
If the offerer wants to request that the answerer accepts a given If the offerer wants to request that the answerer accepts a given
bundled "m=" line only if the answerer keeps the "m=" line within the bundled "m=" line only if the answerer keeps the "m=" line within the
BUNDLE group, the offerer MUST: BUNDLE group, the offerer MUST:
o Associate an SDP 'bundle-only' attribute [Section 8.3.2] with the o Associate an SDP 'bundle-only' attribute [Section 8.2.1] with the
"m=" line; and "m=" line; and
o Assign a zero port value to the "m=" line. o Assign a zero port value to the "m=" line.
NOTE: If the offerer assigns a zero port value to an "m=" line, but NOTE: If the offerer assigns a zero port value to an "m=" line, but
does not also associate an SDP 'bundle-only' attribute with the "m=" does not also associate an SDP 'bundle-only' attribute with the "m="
line, it is an indication that the offerer wants to disable the "m=" line, it is an indication that the offerer wants to disable the "m="
line [Section 8.6.5]. line [Section 8.5.4].
[Section 17.1] shows an example of an initial offer. [Section 17.1] shows an example of an initial offer.
8.3.2. Suggesting the offerer BUNDLE address 8.2.1. Suggesting the offerer BUNDLE address
In the offer, the address associated with the "m=" line associated In the offer, the address associated with the "m=" line associated
with the offerer BUNDLE-tag indicates the address that the offerer with the offerer BUNDLE-tag indicates the address that the offerer
suggests as the offerer BUNDLE address. suggests as the offerer BUNDLE address.
The "m=" line associated with the offerer BUNDLE-tag MUST NOT contain The "m=" line associated with the offerer BUNDLE-tag MUST NOT contain
a zero port value or an SDP 'bundle-only' attribute. a zero port value or an SDP 'bundle-only' attribute.
8.4. Generating the SDP Answer 8.3. Generating the SDP Answer
8.4.1. General
When an answerer generates an answer that contains a BUNDLE group, When an answerer generates an answer that contains a BUNDLE group,
the following general SDP grouping framework restrictions, defined in the following general SDP grouping framework restrictions, defined in
[RFC5888], also apply to the BUNDLE group: [RFC5888], also apply to the BUNDLE group:
o The answerer MUST NOT include a BUNDLE group in the answer, unless o The answerer MUST NOT include a BUNDLE group in the answer, unless
the offerer requested the BUNDLE group to be created in the the offerer requested the BUNDLE group to be created in the
corresponding offer; and corresponding offer; and
o The answerer MUST NOT include an "m=" line within a BUNDLE group, o The answerer MUST NOT include an "m=" line within a BUNDLE group,
unless the offerer requested the "m=" line to be within that unless the offerer requested the "m=" line to be within that
BUNDLE group in the corresponding offer. BUNDLE group in the corresponding offer.
If the answer contains a BUNDLE group, the answerer MUST: If the answer contains a BUNDLE group, the answerer MUST:
o Select an Offerer BUNDLE Address [Section 8.4.2]; and o Select an Offerer BUNDLE Address [Section 8.3.1]; and
o Select an Answerer BUNDLE Address [Section 8.3.2];
o Select an Answerer BUNDLE Address [Section 8.4.3];
The answerer is allowed to select a new Answerer BUNDLE address each The answerer is allowed to select a new Answerer BUNDLE address each
time it generates an answer to an offer. time it generates an answer to an offer.
If the answerer does not want to keep an "m=" line within a BUNDLE If the answerer does not want to keep an "m=" line within a BUNDLE
group, it MUST: group, it MUST:
o Move the "m=" line out of the BUNDLE group [Section 8.4.4]; or o Move the "m=" line out of the BUNDLE group [Section 8.3.3]; or
o Reject the "m=" line [Section 8.4.5]; o Reject the "m=" line [Section 8.3.4];
If the answerer keeps a bundle-only "m=" line within the BUNDLE If the answerer keeps a bundle-only "m=" line within the BUNDLE
group, it follows the procedures (associates the answerer BUNDLE group, it follows the procedures (associates the answerer BUNDLE
address with the "m=" line etc) for any other "m=" line kept within address with the "m=" line etc) for any other "m=" line kept within
the BUNDLE group. the BUNDLE group.
If the answerer does not want to keep a bundle-only "m=" line within If the answerer does not want to keep a bundle-only "m=" line within
the BUNDLE group, it MUST reject the "m=" line [Section 8.4.5]. the BUNDLE group, it MUST reject the "m=" line [Section 8.3.4].
The answerer MUST NOT associate an SDP 'bundle-only' attribute with The answerer MUST NOT associate an SDP 'bundle-only' attribute with
any "m=" line in an answer. any "m=" line in an answer.
NOTE: If a bundled "m=" line in an offer contains a zero port value, NOTE: If a bundled "m=" line in an offer contains a zero port value,
but the "m=" line does not contain an SDP 'bundle-only' attribute, it but the "m=" line does not contain an SDP 'bundle-only' attribute, it
is an indication that the offerer wants to disable the "m=" line is an indication that the offerer wants to disable the "m=" line
[Section 8.6.5]. [Section 8.5.4].
8.4.2. Answerer Selection of Offerer Bundle Address 8.3.1. Answerer Selection of Offerer Bundle Address
In an offer, the address (unique or shared) associated with the In an offer, the address (unique or shared) associated with the
bundled "m=" line associated with the offerer BUNDLE-tag indicates bundled "m=" line associated with the offerer BUNDLE-tag indicates
the address that the offerer suggests as the offerer BUNDLE address the address that the offerer suggests as the offerer BUNDLE address
[Section 8.3.2]. The answerer MUST check whether that "m=" line [Section 8.2.1]. The answerer MUST check whether that "m=" line
fulfils the following criteria: fulfils the following criteria:
o The answerer will not move the "m=" line out of the BUNDLE group o The answerer will not move the "m=" line out of the BUNDLE group
[Section 8.4.4]; and [Section 8.3.3]; and
o The answerer will not reject the "m=" line [Section 8.4.5]; and o The answerer will not reject the "m=" line [Section 8.3.4]; and
o The "m=" line does not contain a zero port value. o The "m=" line does not contain a zero port value.
If all of the criteria above are fulfilled, the answerer MUST select If all of the criteria above are fulfilled, the answerer MUST select
the address associated with the "m=" line as the offerer BUNDLE the address associated with the "m=" line as the offerer BUNDLE
address. In the answer, the answerer BUNDLE-tag represents the "m=" address. In the answer, the answerer BUNDLE-tag represents the "m="
line, and the address associated with the "m=" line in the offer line, and the address associated with the "m=" line in the offer
becomes the offerer BUNDLE address. becomes the offerer BUNDLE address.
If one or more of the criteria are not fulfilled, the answerer MUST If one or more of the criteria are not fulfilled, the answerer MUST
select the next identification-tag in the identification-tag list, select the next identification-tag in the identification-tag list,
and perform the same criteria check for the "m=" line associated with and perform the same criteria check for the "m=" line associated with
that identification-tag. If there are no more identification-tags in that identification-tag. If there are no more identification-tags in
the identification-tag list, the answerer MUST NOT create the BUNDLE the identification-tag list, the answerer MUST NOT create the BUNDLE
group. In addition, unless the answerer rejects the whole offer, the group. In addition, unless the answerer rejects the whole offer, the
answerer MUST apply the answerer procedures for moving an "m=" line answerer MUST apply the answerer procedures for moving an "m=" line
out of a BUNDLE group [Section 8.4.4] to each bundled "m=" line in out of a BUNDLE group [Section 8.3.3] to each bundled "m=" line in
the offer when creating the answer. the offer when creating the answer.
[Section 17.1] shows an example of an offerer BUNDLE address [Section 17.1] shows an example of an offerer BUNDLE address
selection. selection.
8.4.3. Answerer Selection of Answerer BUNDLE Address 8.3.2. Answerer Selection of Answerer BUNDLE Address
When the answerer selects a BUNDLE address for itself, referred to as When the answerer selects a BUNDLE address for itself, referred to as
the answerer BUNDLE address, it MUST associate that address with each the answerer BUNDLE address, it MUST associate that address with each
bundled "m=" line within the created BUNDLE group in the answer. bundled "m=" line within the created BUNDLE group in the answer.
The answerer MUST NOT associate the answerer BUNDLE address with an The answerer MUST NOT associate the answerer BUNDLE address with an
"m=" line that is not within the BUNDLE group, or to an "m=" line "m=" line that is not within the BUNDLE group, or to an "m=" line
that is within another BUNDLE group. that is within another BUNDLE group.
[Section 17.1] shows an example of an answerer BUNDLE address [Section 17.1] shows an example of an answerer BUNDLE address
selection. selection.
8.4.4. Moving A Media Description Out Of A BUNDLE Group 8.3.3. Moving A Media Description Out Of A BUNDLE Group
When an answerer wants to move an "m=" line out of a BUNDLE group, it When an answerer wants to move an "m=" line out of a BUNDLE group, it
MUST first check the following criteria: MUST first check the following criteria:
o In the corresponding offer, the "m=" line is associated with a o In the corresponding offer, the "m=" line is associated with a
shared address (e.g. a previously selected offerer BUNDLE shared address (e.g. a previously selected offerer BUNDLE
address); or address); or
o In the corresponding offer, if an SDP 'bundle-only' attribute is o In the corresponding offer, an SDP 'bundle-only' attribute is
associated with the "m=" line, and if the "m=" line contains a associated with the "m=" line, and the "m=" line contains a zero
zero port value. port value.
If either criteria above is fulfilled, the answerer MUST reject the If either criteria above is fulfilled, the answerer MUST reject the
"m=" line [Section 8.4.5]. "m=" line [Section 8.3.4].
Otherwise, if in the corresponding offer the "m=" line is associated Otherwise, if in the corresponding offer the "m=" line is associated
with a unique address, the answerer MUST associate a unique address with a unique address, the answerer MUST associate a unique address
with the "m=" line in the answer (the answerer does not reject the with the "m=" line in the answer (the answerer does not reject the
"m=" line). "m=" line).
In addition, in either case above, the answerer MUST NOT place the In addition, in either case above, the answerer MUST NOT place the
identification-tag, associated with the moved "m=" line, in the SDP identification-tag, associated with the moved "m=" line, in the SDP
'group' attribute identification-tag list associated with the BUNDLE 'group' attribute identification-tag list associated with the BUNDLE
group. group.
8.4.5. Rejecting A Media Description In A BUNDLE Group 8.3.4. Rejecting A Media Description In A BUNDLE Group
When an answerer rejects an "m=" line, it MUST associate an address When an answerer rejects an "m=" line, it MUST associate an address
with a zero port value with the "m=" line in the answer, according to with a zero port value with the "m=" line in the answer, according to
the procedures in [RFC4566]. the procedures in [RFC3264].
In addition, the answerer MUST NOT place the identification-tag, In addition, the answerer MUST NOT place the identification-tag,
associated with the rejected "m=" line, in the SDP 'group' attribute associated with the rejected "m=" line, in the SDP 'group' attribute
identification-tag list associated with the BUNDLE group. identification-tag list associated with the BUNDLE group.
8.5. Offerer Processing of the SDP Answer 8.4. Offerer Processing of the SDP Answer
When an offerer receives an answer, if the answer contains a BUNDLE When an offerer receives an answer, if the answer contains a BUNDLE
group, the offerer MUST check that any bundled "m=" line in the group, the offerer MUST check that any bundled "m=" line in the
answer was indicated as bundled in the corresponding offer. If there answer was indicated as bundled in the corresponding offer. If there
is no mismatch, the offerer MUST use the offerer BUNDLE address, is no mismatch, the offerer MUST use the offerer BUNDLE address,
selected by the answerer [Section 8.4.2], as the address for each selected by the answerer [Section 8.3.1], as the address for each
bundled "m=" line. bundled "m=" line.
NOTE: As the answerer might reject one or more bundled "m=" lines, or NOTE: As the answerer might reject one or more bundled "m=" lines, or
move a bundled "m=" line out of a BUNDLE group, each bundled "m=" move a bundled "m=" line out of a BUNDLE group, each bundled "m="
line in the offer might not be indicated as bundled in the answer. line in the offer might not be indicated as bundled in the answer.
If the answer does not contain a BUNDLE group, the offerer MUST If the answer does not contain a BUNDLE group, the offerer MUST
process the answer as a normal answer. process the answer as a normal answer.
8.6. Modifying the Session 8.5. Modifying the Session
8.6.1. General
When an offerer generates a subsequent offer, it MUST associate the When an offerer generates a subsequent offer, it MUST associate the
previously selected offerer BUNDLE address [Section 8.4.2] with each previously selected offerer BUNDLE address [Section 8.3.1] with each
bundled "m=" line (including any bundle-only "m=" line), except if: bundled "m=" line (including any bundle-only "m=" line), except if:
o The offerer suggests a new offerer BUNDLE address [Section 8.6.2]; o The offerer suggests a new offerer BUNDLE address [Section 8.5.1];
or or
o The offerer wants to add a bundled "m=" line to the BUNDLE group o The offerer wants to add a bundled "m=" line to the BUNDLE group
[Section 8.6.3]; or [Section 8.5.2]; or
o The offerer wants to move a bundled "m=" line out of the BUNDLE o The offerer wants to move a bundled "m=" line out of the BUNDLE
group [Section 8.6.4]; or group [Section 8.5.3]; or
o The offerer wants to disable the bundled "m=" line o The offerer wants to disable the bundled "m=" line
[Section 8.6.5]. [Section 8.5.4].
In addition, the offerer MUST select an offerer BUNDLE-tag In addition, the offerer MUST select an offerer BUNDLE-tag
[Section 8.3.2] associated with the previously selected offerer [Section 8.2.1] associated with the previously selected offerer
BUNDLE address, unless the offerer suggests a new offerer BUNDLE BUNDLE address, unless the offerer suggests a new offerer BUNDLE
address. address.
8.6.2. Suggesting a new offerer BUNDLE address 8.5.1. Suggesting a new offerer BUNDLE address
When an offerer generates an offer, in which it suggests a new When an offerer generates an offer, in which it suggests a new
offerer BUNDLE address [Section 8.3.2], the offerer MUST: offerer BUNDLE address [Section 8.2.1], the offerer MUST:
o Assign the address (shared address) to each "m=" line within the o Assign the address (shared address) to each "m=" line within the
BUNDLE group; or BUNDLE group; or
o Assign the address (unique address) to one bundled "m=" line. o Assign the address (unique address) to one bundled "m=" line.
In addition, the offerer MUST indicate that the address is the new In addition, the offerer MUST indicate that the address is the new
suggested offerer BUNDLE address [Section 8.3.2]. suggested offerer BUNDLE address [Section 8.2.1].
NOTE: Unless the offerer associates the new suggested offerer BUNDLE NOTE: Unless the offerer associates the new suggested offerer BUNDLE
address with each bundled "m=" line, it can associate unique address with each bundled "m=" line, it can associate unique
addresses with any number of bundled "m=" lines (and the previously addresses with any number of bundled "m=" lines (and the previously
selected offerer BUNDLE address to any remaining bundled "m=" line) selected offerer BUNDLE address to any remaining bundled "m=" line)
if it wants to suggest multiple alternatives for the new offerer if it wants to suggest multiple alternatives for the new offerer
BUNDLE address. BUNDLE address.
8.6.3. Adding a media description to a BUNDLE group 8.5.2. Adding a media description to a BUNDLE group
When an offerer generates an offer, in which it wants to add a When an offerer generates an offer, in which it wants to add a
bundled "m=" line to a BUNDLE group, the offerer MUST: bundled "m=" line to a BUNDLE group, the offerer MUST:
o Assign a unique address to the added "m=" line; or o Assign a unique address to the added "m=" line; or
o Assign the previously selected offerer BUNDLE address to the added o Assign the previously selected offerer BUNDLE address to the added
"m=" line; or "m=" line; or
o If the offerer associates a new (shared address) suggested offerer o If the offerer associates a new (shared address) suggested offerer
BUNDLE address with each bundled "m=" line [Section 8.6.2], also BUNDLE address with each bundled "m=" line [Section 8.5.1], also
associate that address with the added "m=" line. associate that address with the added "m=" line.
In addition, the offerer MUST extend the SDP 'group:BUNDLE' attribute In addition, the offerer MUST extend the SDP 'group:BUNDLE' attribute
identification-tag list with the BUNDLE group [Section 8.3.2] by identification-tag list with the BUNDLE group [Section 8.2.1] by
adding the identification-tag associated with the added "m=" line to adding the identification-tag associated with the added "m=" line to
the list. the list.
NOTE: Assigning a unique address to the "m=" line allows the answerer NOTE: Assigning a unique address to the "m=" line allows the answerer
to move the "m=" line out of the BUNDLE group [Section 8.4.4], to move the "m=" line out of the BUNDLE group [Section 8.3.3],
without having to reject the "m=" line. without having to reject the "m=" line.
If the offerer associates a unique address with the added "m=" line, If the offerer associates a unique address with the added "m=" line,
and if the offerer suggests that address as the new offerer BUNDLE and if the offerer suggests that address as the new offerer BUNDLE
address [Section 8.6.2], the offerer BUNDLE-tag MUST represent the address [Section 8.5.1], the offerer BUNDLE-tag MUST represent the
added "m=" line [Section 8.3.2]. added "m=" line [Section 8.2.1].
If the offerer associates a new suggested offerer BUNDLE address with If the offerer associates a new suggested offerer BUNDLE address with
each bundled "m=" line [Section 8.6.2], including the added "m=" each bundled "m=" line [Section 8.5.1], including the added "m="
line, the offerer BUNDLE-tag MAY represent the added "m=" line line, the offerer BUNDLE-tag MAY represent the added "m=" line
[Section 8.3.2]. [Section 8.2.1].
[Section 17.3] shows an example where an offerer sends an offer in [Section 17.3] shows an example where an offerer sends an offer in
order to add a bundled "m=" line to a BUNDLE group. order to add a bundled "m=" line to a BUNDLE group.
8.6.4. Moving A Media Description Out Of A BUNDLE Group 8.5.3. Moving A Media Description Out Of A BUNDLE Group
When an offerer generates an offer, in which it wants to move a When an offerer generates an offer, in which it wants to move a
bundled "m=" line out of a BUNDLE group it was added to in a previous bundled "m=" line out of a BUNDLE group it was added to in a previous
offer/answer transaction, the offerer: offer/answer transaction, the offerer:
o MUST associate a unique address with the "m=" line; and o MUST associate a unique address with the "m=" line; and
o MUST NOT place the identification-tag associated with the "m=" o MUST NOT place the identification-tag associated with the "m="
line in the SDP 'group:BUNDLE' attribute identification-tag list line in the SDP 'group:BUNDLE' attribute identification-tag list
associated with the BUNDLE group. associated with the BUNDLE group.
NOTE: If the removed "m=" line is associated with the previously NOTE: If the removed "m=" line is associated with the previously
selected BUNDLE-tag, the offerer needs to suggest a new BUNDLE-tag selected BUNDLE-tag, the offerer needs to suggest a new BUNDLE-tag
[Section 8.3.2]. [Section 8.2.1].
NOTE: If an "m=" line, when being moved out of a BUNDLE group, is NOTE: If an "m=" line, when being moved out of a BUNDLE group, is
added to another BUNDLE group, the offerer applies the procedures in added to another BUNDLE group, the offerer applies the procedures in
[Section 8.6.3] to the "m=" line. [Section 8.5.2] to the "m=" line.
[Section 17.4] shows an example of an offer for moving an "m=" line [Section 17.4] shows an example of an offer for moving an "m=" line
out of a BUNDLE group. out of a BUNDLE group.
8.6.5. Disabling A Media Description In A BUNDLE Group 8.5.4. Disabling A Media Description In A BUNDLE Group
When an offerer generates an offer, in which it wants to disable a When an offerer generates an offer, in which it wants to disable a
bundled "m=" line (added to the BUNDLE group in a previous offer/ bundled "m=" line (added to the BUNDLE group in a previous offer/
answer transaction), the offerer: answer transaction), the offerer:
o MUST associate an address with a zero port value with the "m=" o MUST associate an address with a zero port value with the "m="
line, following the procedures in [RFC4566]; and line, following the procedures in [RFC4566]; and
o MUST NOT place the identification-tag associated with the "m=" o MUST NOT place the identification-tag associated with the "m="
line in the SDP 'group:BUNDLE' attribute identification-tag list line in the SDP 'group:BUNDLE' attribute identification-tag list
associated with the BUNDLE group. associated with the BUNDLE group.
[Section 17.5] shows an example of an offer for disabling an "m=" [Section 17.5] shows an example of an offer for disabling an "m="
line within a BUNDLE group. line within a BUNDLE group.
9. Protocol Identification 9. Protocol Identification
9.1. General
Each "m=" line within a BUNDLE group MUST use the same transport- Each "m=" line within a BUNDLE group MUST use the same transport-
layer protocol. If bundled "m=" lines use different protocols on top layer protocol. If bundled "m=" lines use different protocols on top
of the transport-layer protocol, there MUST exist a publicly of the transport-layer protocol, there MUST exist a publicly
available specification which describes a mechanism, for this available specification which describes a mechanism, for this
particular protocol combination, how to associate received data with particular protocol combination, how to associate received data with
the correct protocol. the correct protocol.
In addition, if received data can be associated with more than one In addition, if received data can be associated with more than one
bundled "m=" line, there MUST exist a publicly available bundled "m=" line, there MUST exist a publicly available
specification which describes a mechanism for associating the specification which describes a mechanism for associating the
received data with the correct "m=" line. received data with the correct "m=" line.
This document describes a mechanism to identify the protocol of This document describes a mechanism to identify the protocol of
received data among the STUN, DTLS and SRTP protocols (in any received data among the STUN, DTLS and SRTP protocols (in any
combination), when UDP is used as transport-layer protocol, but does combination), when UDP is used as transport-layer protocol, but does
not describe how to identify different protocols transported on DTLS. not describe how to identify different protocols transported on DTLS.
While the mechanism is generally applicable to other protocols and While the mechanism is generally applicable to other protocols and
transport-layers protocols, any such use requires further transport-layer protocols, any such use requires further
specification around how to multiplex multiple protocols on a given specification around how to multiplex multiple protocols on a given
transport-layer protocols, and how to associate received data with transport-layer protocol, and how to associate received data with the
the correct protocols. correct protocols.
9.2. STUN, DTLS, SRTP 9.1. STUN, DTLS, SRTP
Section 5.1.2 of [RFC5764] describes a mechanism to identify the Section 5.1.2 of [RFC5764] describes a mechanism to identify the
protocol of a received packet among the STUN, Datagram Transport protocol of a received packet among the STUN, Datagram Transport
Layer Security (DTLS) and SRTP protocols (in any combination). If an Layer Security (DTLS) and SRTP protocols (in any combination). If an
offer or answer includes bundled "m=" lines that represent these offer or answer includes bundled "m=" lines that represent these
protocols, the offerer or answerer MUST support the mechanism protocols, the offerer or answerer MUST support the mechanism
described in [RFC5764], and no explicit negotiation is required in described in [RFC5764], and no explicit negotiation is required in
order to indicate support and usage of the mechanism. order to indicate support and usage of the mechanism.
[RFC5764] does not describe how to identify different protocols [RFC5764] does not describe how to identify different protocols
skipping to change at page 18, line 35 skipping to change at page 18, line 9
describes a mechanism for associating the received DTLS packet with describes a mechanism for associating the received DTLS packet with
the correct "m=" line. the correct "m=" line.
[Section 10.2] describes how to associate a received (S)RTP packet [Section 10.2] describes how to associate a received (S)RTP packet
with the correct "m=" line. with the correct "m=" line.
10. RTP Considerations 10. RTP Considerations
10.1. Single RTP Session 10.1. Single RTP Session
10.1.1. General
All RTP-based media within a single BUNDLE group belong to a single All RTP-based media within a single BUNDLE group belong to a single
RTP session [RFC3550]. Disjoint BUNDLE groups will form multiple RTP RTP session [RFC3550]. Disjoint BUNDLE groups will form multiple RTP
sessions, one per BUNDLE group. sessions, one per BUNDLE group.
Since a single RTP session is used for each bundle group, all "m=" Since a single RTP session is used for each bundle group, all "m="
lines representing RTP-based media in a bundle group will share a lines representing RTP-based media in a bundle group will share a
single SSRC numbering space [RFC3550]. single SSRC numbering space [RFC3550].
The following rules and restrictions apply for a single RTP session: The following rules and restrictions apply for a single RTP session:
o A specific payload type value can be used in multiple bundled "m=" o A specific payload type value can be used in multiple bundled "m="
lines if each codec associated with the payload type number shares lines if each codec associated with the payload type number shares
an identical codec configuration [Section 10.1.2]. an identical codec configuration [Section 10.1.1].
o The proto value in each bundled RTP-based "m=" line MUST be o The proto value in each bundled RTP-based "m=" line MUST be
identical (e.g. RTP/AVPF). identical (e.g. RTP/AVPF).
o The RTP MID header extension MUST be enabled, by associating an o The RTP MID header extension MUST be enabled, by associating an
SDP 'extmap' attribute [RFC5285], with a 'urn:ietf:params:rtp- SDP 'extmap' attribute [RFC5285], with a 'urn:ietf:params:rtp-
hdrext:sdes:mid' URI value, with each bundled RTP-based "m=" line hdrext:sdes:mid' URI value, with each bundled RTP-based "m=" line
in every offer and answer. in every offer and answer.
o A given SSRC MUST NOT transmit RTP packets using payload types o A given SSRC MUST NOT transmit RTP packets using payload types
skipping to change at page 19, line 26 skipping to change at page 18, line 44
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 fail to function. Even if done in with time overlap, RTP and RTCP fail to function. Even if done in
proper sequence this causes RTP Timestamp rate switching issues proper sequence this causes RTP Timestamp rate switching issues
[RFC7160]. However, once an SSRC has left the RTP session (by [RFC7160]. However, once an SSRC has left the RTP session (by
sending an RTCP BYE packet), that SSRC can be reused by another sending an RTCP BYE packet), that SSRC can be reused by another
source (possibly associated with a different bundled "m=" line) after source (possibly associated with a different bundled "m=" line) after
a delay of 5 RTCP reporting intervals (the delay is to ensure the a delay of 5 RTCP reporting intervals (the delay is to ensure the
SSRC has timed out, in case the RTCP BYE packet was lost [RFC3550]). SSRC has timed out, in case the RTCP BYE packet was lost [RFC3550]).
10.1.2. Payload Type (PT) Value Reuse 10.1.1. Payload Type (PT) Value Reuse
Multiple bundled "m=" lines might represent RTP based media. As all Multiple bundled "m=" lines might represent RTP based media. As all
RTP based media specified by a BUNDLE group belong to the same RTP RTP based media specified by a BUNDLE group belong to the same RTP
session, in order for a given payload type value to be used inside session, in order for a given payload type value to be used inside
more than one bundled "m=" line, all codecs associated with the more than one bundled "m=" line, all codecs associated with the
payload type number MUST share an identical codec configuration. payload type number MUST share an identical codec configuration.
This means that the codecs MUST share the same media type, encoding This means that the codecs MUST share the same media type, encoding
name, clock rate and any parameter that can affect the codec name, clock rate and any parameter that can affect the codec
configuration and packetization. configuration and packetization.
[I-D.ietf-mmusic-sdp-mux-attributes] lists SDP attributes, whose [I-D.ietf-mmusic-sdp-mux-attributes] lists SDP attributes, whose
skipping to change at page 20, line 5 skipping to change at page 19, line 23
line. Such mechanisms include using the payload type value carried line. Such mechanisms include using the payload type value carried
inside the RTP packets, the SSRC values carried inside the RTP inside the RTP packets, the SSRC values carried inside the RTP
packets, and other "m=" line specific information carried inside the packets, and other "m=" line specific information carried inside the
RTP packets. RTP packets.
As all RTP/RTCP packets associated with a BUNDLE group are received As all RTP/RTCP packets associated with a BUNDLE group are received
(and sent) using single address:port combinations, the local (and sent) using single address:port combinations, the local
address:port combination cannot be used to associate received RTP address:port combination cannot be used to associate received RTP
packets with the correct "m=" line. packets with the correct "m=" line.
As described in [Section 10.1.2], the same payload type value might As described in [Section 10.1.1], the same payload type value might
be used inside RTP packets described by multiple "m=" lines. In such be used inside RTP packets described by multiple "m=" lines. In such
cases, the payload type value cannot be used to associate received cases, the payload type value cannot be used to associate received
RTP packets with the correct "m=" line. RTP packets with the correct "m=" line.
An offerer and answerer can inform each other which SSRC values they An offerer and answerer can inform each other which SSRC values they
will use for RTP and RTCP by using the SDP 'ssrc' attribute will use for RTP and RTCP by using the SDP 'ssrc' attribute
[RFC5576]. To allow for proper association with this mechanism, the [RFC5576]. To allow for proper association with this mechanism, the
'ssrc' attribute needs to be associated with each "m=" line that 'ssrc' attribute needs to be associated with each "m=" line that
shares a payload type with any other "m=" line in the same bundle. shares a payload type with any other "m=" line in the same bundle.
As the SSRC values will be carried inside the RTP/RTCP packets, the As the SSRC values will be carried inside the RTP/RTCP packets, the
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In order for an offerer and answerer to always be able to associate In order for an offerer and answerer to always be able to associate
received RTP and RTCP packets with the correct "m=" line, an offerer received RTP and RTCP packets with the correct "m=" line, an offerer
and answerer using the BUNDLE extension MUST support the mechanism and answerer using the BUNDLE extension MUST support the mechanism
defined in Section 14, where the remote endpoint inserts the defined in Section 14, where the remote endpoint inserts the
identification-tag associated with an "m=" line in RTP and RTCP identification-tag associated with an "m=" line in RTP and RTCP
packets associated with that "m=" line. packets associated with that "m=" line.
10.3. RTP/RTCP Multiplexing 10.3. RTP/RTCP Multiplexing
10.3.1. General
Within a BUNDLE group, the offerer and answerer MUST enable RTP/RTCP Within a BUNDLE group, the offerer and answerer MUST enable RTP/RTCP
multiplexing [RFC5761] for the RTP-based media specified by the multiplexing [RFC5761] for the RTP-based media specified by the
BUNDLE group. BUNDLE group.
When RTP/RTCP multiplexing is enabled, the same address:port When RTP/RTCP multiplexing is enabled, the same address:port
combination will be used for sending all RTP packets and the RTCP combination will be used for sending all RTP packets and the RTCP
packets associated with the BUNDLE group. Each endpoint will send packets associated with the BUNDLE group. Each endpoint will send
the packets towards the BUNDLE address of the other endpoint. The the packets towards the BUNDLE address of the other endpoint. The
same address:port combination MAY be used for receiving RTP packets same address:port combination MAY be used for receiving RTP packets
and RTCP packets. and RTCP packets.
10.3.2. SDP Offer/Answer Procedures 10.3.1. SDP Offer/Answer Procedures
10.3.2.1. General
This section describes how an offerer and answerer use the SDP 'rtcp- This section describes how an offerer and answerer use the SDP 'rtcp-
mux' attribute [RFC5761] and the SDP 'rtcp-mux-only' attribute mux' attribute [RFC5761] and the SDP 'rtcp-mux-only' attribute
[I-D.ietf-mmusic-mux-exclusive] to negotiate usage of RTP/RTCP [I-D.ietf-mmusic-mux-exclusive] to negotiate usage of RTP/RTCP
multiplexing for RTP-based media specified by a BUNDLE group. multiplexing for RTP-based media specified by a BUNDLE group.
The procedures in this section only apply to RTP-based "m=" lines. The procedures in this section only apply to RTP-based "m=" lines.
10.3.2.2. Generating the Initial SDP Offer 10.3.1.1. Generating the Initial SDP Offer
When an offerer generates an initial offer, the offerer MUST When an offerer generates an initial offer, the offerer MUST
associate either an SDP 'rtcp-mux' attribute [RFC5761] or an SDP associate either an SDP 'rtcp-mux' attribute [RFC5761] or an SDP
'rtcp-mux-only' attribute [I-D.ietf-mmusic-mux-exclusive] with each 'rtcp-mux-only' attribute [I-D.ietf-mmusic-mux-exclusive] with each
bundled RTP-based "m=" line in the offer. The offerer MUST associate bundled RTP-based "m=" line in the offer. The offerer MUST associate
an SDP 'rtcp-mux-only' attribute with each bundle-only "m=" line. If an SDP 'rtcp-mux-only' attribute with each bundle-only "m=" line. If
the offerer associates a 'rtcp-mux-only' attribute with an "m=" line, the offerer associates a 'rtcp-mux-only' attribute with an "m=" line,
the offerer may also associate a 'rtcp-mux' attribute with the same the offerer may also associate a 'rtcp-mux' attribute with the same
"m=" line, as described in [I-D.ietf-mmusic-mux-exclusive]. "m=" line, as described in [I-D.ietf-mmusic-mux-exclusive].
skipping to change at page 21, line 40 skipping to change at page 21, line 9
[RFC3605] with a bundled "m=" line, excluding a bundle-only "m=" [RFC3605] with a bundled "m=" line, excluding a bundle-only "m="
line, in order to provide a fallback port for RTCP, as described in line, in order to provide a fallback port for RTCP, as described in
[RFC5761]. However, the fallback port will only be used in case the [RFC5761]. However, the fallback port will only be used in case the
answerer does not include the "m=" line in the BUNDLE group in the answerer does not include the "m=" line in the BUNDLE group in the
associated answer. associated answer.
In the initial offer, the address:port combination for RTCP MUST be In the initial offer, the address:port combination for RTCP MUST be
unique in each bundled RTP-based "m=" line (excluding a 'bundle-only' unique in each bundled RTP-based "m=" line (excluding a 'bundle-only'
"m=" line), similar to RTP. "m=" line), similar to RTP.
10.3.2.3. Generating the SDP Answer 10.3.1.2. Generating the SDP Answer
When an answerer generates an answer, if the answerer accepts one or When an answerer generates an answer, if the answerer accepts one or
more RTP-based "m=" lines within a BUNDLE group, the answerer MUST more RTP-based "m=" lines within a BUNDLE group, the answerer MUST
enable usage of RTP/RTCP multiplexing. The answerer MUST associate enable usage of RTP/RTCP multiplexing. The answerer MUST associate
an SDP "rtcp-mux" attribute with each RTP-based "m=" line in the an SDP "rtcp-mux" attribute with each RTP-based "m=" line in the
answer. In addition, if an "m=" line in the corresponding offer answer. In addition, if an "m=" line in the corresponding offer
contained an SDP "rtcp-mux-only" attribute, the answerer MUST also contained an SDP "rtcp-mux-only" attribute, the answerer MUST also
associate an SDP "rtcp-mux-only" attribute with the "m=" line in the associate an SDP "rtcp-mux-only" attribute with the "m=" line in the
answer. answer.
If an RTP-based "m=" line in the corresponding offer did not contain If an RTP-based "m=" line in the corresponding offer did not contain
an SDP "rtcp-mux" attribute or an SDP "rtcp-mux-only" attribute, the an SDP "rtcp-mux" attribute or an SDP "rtcp-mux-only" attribute, the
answerer MUST NOT include the "m=" line within a BUNDLE group in the answerer MUST NOT include the "m=" line within a BUNDLE group in the
answer. answer.
If an RTP-based "m=" line in the corresponding offer contained an SDP If an RTP-based "m=" line in the corresponding offer contained an SDP
"rtcp-mux-only" attribute, and if the answerer moves the "m=" line "rtcp-mux-only" attribute, and if the answerer moves the "m=" line
out of the BUNDLE group in the answer Section 8.4.4, the answerer out of the BUNDLE group in the answer Section 8.3.3, the answerer
MUST still either enable RTP/RTCP multiplexing for the media MUST still either enable RTP/RTCP multiplexing for the media
associated with the "m=" line, or reject the "m=" line Section 8.4.5. associated with the "m=" line, or reject the "m=" line Section 8.3.4.
The answerer MUST NOT associate an SDP 'rtcp' attribute with any The answerer MUST NOT associate an SDP 'rtcp' attribute with any
bundled "m=" line in the answer. The answerer will use the port bundled "m=" line in the answer. The answerer will use the port
value of the selected offerer BUNDLE address for sending RTP and RTCP value of the selected offerer BUNDLE address for sending RTP and RTCP
packets associated with each RTP-based bundled "m=" line towards the packets associated with each RTP-based bundled "m=" line towards the
offerer. offerer.
If the usage of RTP/RTCP multiplexing within a BUNDLE group has been If the usage of RTP/RTCP multiplexing within a BUNDLE group has been
negotiated in a previous offer/answer transaction, the answerer MUST negotiated in a previous offer/answer transaction, the answerer MUST
associate an SDP 'rtcp-mux' attribute with each bundled RTP-based associate an SDP 'rtcp-mux' attribute with each bundled RTP-based
"m=" line in the answer. "m=" line in the answer.
10.3.2.4. Offerer Processing of the SDP Answer 10.3.1.3. Offerer Processing of the SDP Answer
When an offerer receives an answer, if the answerer has accepted the When an offerer receives an answer, if the answerer has accepted the
usage of RTP/RTCP multiplexing (see Section 10.3.2.3), the answerer usage of RTP/RTCP multiplexing (see Section 10.3.1.2), the answerer
follows the procedures for RTP/RTCP multiplexing defined in follows the procedures for RTP/RTCP multiplexing defined in
[RFC5761]. The offerer will use the port value associated with the [RFC5761]. The offerer will use the port value associated with the
answerer BUNDLE address for sending RTP and RTCP packets associated answerer BUNDLE address for sending RTP and RTCP packets associated
with each RTP-based bundled "m=" line towards the answerer. with each RTP-based bundled "m=" line towards the answerer.
NOTE: It is considered a protocol error if the answerer has not NOTE: It is considered a protocol error if the answerer has not
accepted the usage of RTP/RTCP multiplexing for RTP-based "m=" lines accepted the usage of RTP/RTCP multiplexing for RTP-based "m=" lines
that the answerer included in the BUNDLE group. that the answerer included in the BUNDLE group.
10.3.2.5. Modifying the Session 10.3.1.4. Modifying the Session
When an offerer generates a subsequent offer, it MUST associate an When an offerer generates a subsequent offer, it MUST associate an
SDP 'rtcp-mux' attribute or an SDP 'rtcp-mux-only' attribute with SDP 'rtcp-mux' attribute or an SDP 'rtcp-mux-only' attribute with
each RTP-based bundled "m=" line within the BUNDLE group (including each RTP-based bundled "m=" line within the BUNDLE group (including
any bundled RTP-based "m=" line that the offerer wants to add to the any bundled RTP-based "m=" line that the offerer wants to add to the
BUNDLE group), unless the offerer wants to disable or remove the "m=" BUNDLE group), unless the offerer wants to disable or remove the "m="
line from the BUNDLE group. line from the BUNDLE group.
11. ICE Considerations 11. ICE Considerations
11.1. 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 [I-D.ietf-ice-rfc5245bis]. mechanism [I-D.ietf-ice-rfc5245bis].
The generic procedures for negotiating usage of ICE using SDP, The generic procedures for negotiating usage of ICE using SDP,
defined in [I-D.ietf-mmusic-ice-sip-sdp], also apply to usage of ICE defined in [I-D.ietf-mmusic-ice-sip-sdp], also apply to usage of ICE
with BUNDLE, with the following exceptions: with BUNDLE, with the following exceptions:
o When BUNDLE addresses for a BUNDLE group have been selected for o When BUNDLE addresses for a BUNDLE group have been selected for
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offerer BUNDLE-tag. offerer BUNDLE-tag.
o Among bundled "m=" lines with which the answerer has associated a o Among bundled "m=" lines with which the answerer has associated a
shared address, the answerer only associates ICE-related media- shared address, the answerer only associates ICE-related media-
level SDP attributes with the "m=" line associated with the level SDP attributes with the "m=" line associated with the
answerer BUNDLE-tag. answerer BUNDLE-tag.
Support and usage of ICE mechanism together with the BUNDLE extension Support and usage of ICE mechanism together with the BUNDLE extension
is OPTIONAL. is OPTIONAL.
11.2. SDP Offer/Answer Procedures 11.1. SDP Offer/Answer Procedures
11.2.1. General
When an offerer associates a unique address with a bundled "m=" line When an offerer associates a unique address with a bundled "m=" line
(excluding any bundle-only "m=" line), the offerer MUST associate SDP (excluding any bundle-only "m=" line), the offerer MUST associate SDP
'candidate' attributes (and other applicable ICE-related media-level 'candidate' attributes (and other applicable ICE-related media-level
SDP attributes), containing unique ICE properties (candidates etc), SDP attributes), containing unique ICE properties (candidates etc),
with the "m=" line, according to the procedures in with the "m=" line, according to the procedures in
[I-D.ietf-mmusic-ice-sip-sdp]. [I-D.ietf-mmusic-ice-sip-sdp].
When an offerer associates a shared address with a bundled "m=" line, When an offerer associates a shared address with a bundled "m=" line,
if the "m=" line is associated with the offerer BUNDLE-tag, the if the "m=" line is associated with the offerer BUNDLE-tag, the
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When an answerer associates a shared address with a bundled "m=" When an answerer associates a shared address with a bundled "m="
line, if the "m=" line is associated with the answerer BUNDLE-tag, line, if the "m=" line is associated with the answerer BUNDLE-tag,
the answerer MUST associate SDP 'candidate' attributes (and other the answerer MUST associate SDP 'candidate' attributes (and other
applicable ICE-related media-level SDP attributes), containing shared applicable ICE-related media-level SDP attributes), containing shared
ICE properties, with the "m=" line. If the "m=" line is not ICE properties, with the "m=" line. If the "m=" line is not
associated with the answerer BUNDLE-tag, the answerer MUST NOT associated with the answerer BUNDLE-tag, the answerer MUST NOT
associate ICE-related SDP attributes with the "m=" line. associate ICE-related SDP attributes with the "m=" line.
NOTE: As most ICE-related media-level SDP attributes belong to the NOTE: As most ICE-related media-level SDP attributes belong to the
TRANSPORT mux category [I-D.ietf-mmusic-sdp-mux-attributes], the TRANSPORT mux category [I-D.ietf-mmusic-sdp-mux-attributes], the
offerer and answerer follow the rules in Section 8.2. However, in offerer and answerer follow the rules in Section 8.1. However, in
the case of ICE-related media-level attributes, the rules apply to the case of ICE-related media-level attributes, the rules apply to
all attributes (see note below), even if they belong to a different all attributes (see note below), even if they belong to a different
mux category. mux category.
NOTE: The following ICE-related media-level SDP attributes are NOTE: The following ICE-related media-level SDP attributes are
defined in [I-D.ietf-mmusic-ice-sip-sdp]: 'candidiate', 'remote- defined in [I-D.ietf-mmusic-ice-sip-sdp]: 'candidiate', 'remote-
candidates', 'ice-mismatch', 'ice-ufrag', 'ice-pwd', and 'ice- candidates', 'ice-mismatch', 'ice-ufrag', 'ice-pwd', and 'ice-
pacing'. pacing'.
11.2.2. Generating the Initial SDP Offer 11.1.1. Generating the Initial SDP Offer
When an offerer generates an initial offer, the offerer MUST When an offerer generates an initial offer, the offerer MUST
associate ICE-related media-level SDP attributes with each bundled associate ICE-related media-level SDP attributes with each bundled
"m=" line, according to [Section 11.2.1]. "m=" line, according to [Section 11.1].
11.2.3. Generating the SDP Answer 11.1.2. Generating the SDP Answer
When an answerer generates an answer that contains a BUNDLE group, When an answerer generates an answer that contains a BUNDLE group,
the answerer MUST associated ICE-related SDP attributes with the "m=" the answerer MUST associate ICE-related SDP attributes with the "m="
line associated with the answerer BUNDLE-tag, according to line associated with the answerer BUNDLE-tag, according to
[Section 11.2.1]. [Section 11.1].
11.2.4. Offerer Processing of the SDP Answer 11.1.3. Offerer Processing of the SDP Answer
When an offerer receives an answer, if the answerer supports and uses When an offerer receives an answer, if the answerer supports and uses
the ICE mechanism and the BUNDLE extension, the offerer MUST the ICE mechanism and the BUNDLE extension, the offerer MUST
associate the ICE properties associated with the offerer BUNDLE associate the ICE properties associated with the offerer BUNDLE
address, selected by the answerer [Section 8.4.2], with each bundled address, selected by the answerer [Section 8.3.1], with each bundled
"m=" line. "m=" line.
11.2.5. Modifying the Session 11.1.4. Modifying the Session
When an offerer generates a subsequent offer, it MUST associated When an offerer generates a subsequent offer, it MUST associate
unique or shared ICE properties to one or more bundled "m=" lines, unique or shared ICE properties to one or more bundled "m=" lines,
according to [Section 11.2.1]. according to [Section 11.1].
12. DTLS Considerations 12. DTLS Considerations
One or more media streams within a BUNDLE group might use the One or more media streams within a BUNDLE group might use the
Datagram Transport Layer Security (DTLS) protocol [RFC6347] in order Datagram Transport Layer Security (DTLS) protocol [RFC6347] in order
to encrypt the data, or to negotiate encryption keys if another to encrypt the data, or to negotiate encryption keys if another
encryption mechanism is used to encrypt media. encryption mechanism is used to encrypt media.
When DTLS is used within a BUNDLE group, the following rules apply: When DTLS is used within a BUNDLE group, the following rules apply:
o There can only be one DTLS association [RFC6347] associated with o There can only be one DTLS association [RFC6347] associated with
the BUNDLE group; and the BUNDLE group; and
o Each usage of the DTLS association within the BUNDLE group MUST o Each usage of the DTLS association within the BUNDLE group MUST
use the same mechanism for determining which endpoints (the use the same mechanism for determining which endpoints (the
offerer or answerer) becomes DTLS client and DTLS server; and offerer or answerer) become DTLS client and DTLS server; and
o Each usage of the DTLS association within the Bundle group MUST o Each usage of the DTLS association within the Bundle group MUST
use the same mechanism for determining whether an offer or answer use the same mechanism for determining whether an offer or answer
will trigger the establishment of a new DTLS association, or will trigger the establishment of a new DTLS association, or
whether an existing DTLS association will be used; and whether an existing DTLS association will be used; and
o If the DTLS client supports DTLS-SRTP [RFC5764] it MUST include o If the DTLS client supports DTLS-SRTP [RFC5764] it MUST include
the 'use_srtp' extension [RFC5764] in the DTLS ClientHello message the 'use_srtp' extension [RFC5764] in the DTLS ClientHello message
[RFC5764], The client MUST include the extension even if the usage [RFC5764], The client MUST include the extension even if the usage
of DTLS-SRTP is not negotiated as part of the multimedia session of DTLS-SRTP is not negotiated as part of the multimedia session
(e.g. SIP session [RFC3261]. (e.g., SIP session [RFC3261].
NOTE: The inclusion of the 'use_srtp' extension during the initial NOTE: The inclusion of the 'use_srtp' extension during the initial
DTLS handshake ensures that a DTLS renegotiation will not be required DTLS handshake ensures that a DTLS renegotiation will not be required
in order to include the extension, in case DTLS-SRTP encrypted media in order to include the extension, in case DTLS-SRTP encrypted media
is added to the BUNDLE group later during the multimedia session. is added to the BUNDLE group later during the multimedia session.
13. Update to RFC 3264 13. Update to RFC 3264
13.1. General
This section replaces the text of the following sections of RFC 3264: This section replaces the text of the following sections of RFC 3264:
o Section 5.1 (Unicast Streams). o Section 5.1 (Unicast Streams).
o Section 8.2 (Removing a Media Stream). o Section 8.2 (Removing a Media Stream).
o Section 8.4 (Putting a Unicast Media Stream on Hold). o Section 8.4 (Putting a Unicast Media Stream on Hold).
13.2. Original text of section 5.1 (2nd paragraph) of RFC 3264 13.1. Original text of section 5.1 (2nd paragraph) of RFC 3264
For recvonly and sendrecv streams, the port number and address in the For recvonly and sendrecv streams, the port number and address in the
offer indicate where the offerer would like to receive the media offer indicate where the offerer would like to receive the media
stream. For sendonly RTP streams, the address and port number stream. For sendonly RTP streams, the address and port number
indirectly indicate where the offerer wants to receive RTCP reports. indirectly indicate where the offerer wants to receive RTCP reports.
Unless there is an explicit indication otherwise, reports are sent to Unless there is an explicit indication otherwise, reports are sent to
the port number one higher than the number indicated. The IP address the port number one higher than the number indicated. The IP address
and port present in the offer indicate nothing about the source IP 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 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 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 stream is offered but MUST NOT be used. This has no useful semantics
in an initial offer, but is allowed for reasons of completeness, in an initial offer, but is allowed for reasons of completeness,
since the answer can contain a zero port indicating a rejected stream since the answer can contain a zero port indicating a rejected stream
(Section 6). Furthermore, existing streams can be terminated by (Section 6). Furthermore, existing streams can be terminated by
setting the port to zero (Section 8). In general, a port number of setting the port to zero (Section 8). In general, a port number of
zero indicates that the media stream is not wanted. zero indicates that the media stream is not wanted.
13.3. New text replacing section 5.1 (2nd paragraph) of RFC 3264 13.2. New text replacing section 5.1 (2nd paragraph) of RFC 3264
For recvonly and sendrecv streams, the port number and address in the For recvonly and sendrecv streams, the port number and address in the
offer indicate where the offerer would like to receive the media offer indicate where the offerer would like to receive the media
stream. For sendonly RTP streams, the address and port number stream. For sendonly RTP streams, the address and port number
indirectly indicate where the offerer wants to receive RTCP reports. indirectly indicate where the offerer wants to receive RTCP reports.
Unless there is an explicit indication otherwise, reports are sent to Unless there is an explicit indication otherwise, reports are sent to
the port number one higher than the number indicated. The IP address the port number one higher than the number indicated. The IP address
and port present in the offer indicate nothing about the source IP 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 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 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 that the stream is offered but MUST NOT be used, but an extension
mechanism might specify different semantics for the usage of a zero mechanism might specify different semantics for the usage of a zero
port value. Furthermore, existing streams can be terminated by port value. Furthermore, existing streams can be terminated by
setting the port to zero (Section 8). In general, a port number of setting the port to zero (Section 8). In general, a port number of
zero by default indicates that the media stream is not wanted. zero by default indicates that the media stream is not wanted.
13.4. Original text of section 8.2 (2nd paragraph) of RFC 3264 13.3. 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 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 zero in the answer. Like the offer, the answer MAY omit all
attributes present previously, and MAY list just a single media attributes present previously, and MAY list just a single media
format from amongst those in the offer. format from amongst those in the offer.
13.5. New text replacing section 8.2 (2nd paragraph) of RFC 3264 13.4. 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 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, marked with port zero in the answer, unless an extension mechanism,
which specifies semantics for the usage of a non-zero port value, is which specifies semantics for the usage of a non-zero port value, is
used. If the stream is marked with port zero in the answer, the used. If the stream is marked with port zero in the answer, the
answer MAY omit all attributes present previously, and MAY list just answer MAY omit all attributes present previously, and MAY list just
a single media format from amongst those in the offer." a single media format from amongst those in the offer."
13.6. Original text of section 8.4 (6th paragraph) of RFC 3264 13.5. Original text of section 8.4 (6th paragraph) of RFC 3264
RFC 2543 [10] specified that placing a user on hold was accomplished 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 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 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 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 with connection oriented media. However, it can be useful in an
initial offer when the offerer knows it wants to use a particular set 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 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 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 number MUST NOT be zero, which would specify that the stream has been
disabled. An agent MUST be capable of receiving SDP with a 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 connection address of 0.0.0.0, in which case it means that neither
RTP nor RTCP should be sent to the peer. RTP nor RTCP should be sent to the peer.
13.7. New text replacing section 8.4 (6th paragraph) of RFC 3264 13.6. New text replacing section 8.4 (6th paragraph) of RFC 3264
RFC 2543 [10] specified that placing a user on hold was accomplished 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 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 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 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 with connection oriented media. However, it can be useful in an
initial offer when the offerer knows it wants to use a particular set 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 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 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 number MUST NOT be zero, if it would specify that the stream has been
disabled. However, an extension mechanism might specify different disabled. However, an extension mechanism might specify different
semantics of the zero port number usage. An agent MUST be capable of 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 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. means that neither RTP nor RTCP should be sent to the peer.
14. RTP/RTCP extensions for identification-tag transport 14. RTP/RTCP extensions for identification-tag transport
14.1. General
SDP Offerers and Answerers [RFC3264] can associate identification- SDP Offerers and Answerers [RFC3264] can associate identification-
tags with "m=" lines within SDP Offers and Answers, using the tags with "m=" lines within SDP Offers and Answers, using the
procedures in [RFC5888]. Each identification-tag uniquely represents procedures in [RFC5888]. Each identification-tag uniquely represents
an "m=" line. an "m=" line.
This section defines a new RTCP SDES item [RFC3550], 'MID', which is This section defines a new RTCP SDES item [RFC3550], 'MID', which is
used to carry identification-tags within RTCP SDES packets. This used to carry identification-tags within RTCP SDES packets. This
section also defines a new RTP header extension [RFC5285], which is section also defines a new RTP SDES header extension
used to carry identification-tags in RTP packets. [I-D.ietf-avtext-sdes-hdr-ext], which is used to carry the 'MID' RTCP
SDES item in RTP packets.
The SDES item and RTP header extension make it possible for a The SDES item and RTP SDES header extension make it possible for a
receiver to associate received RTCP- and RTP packets with a specific receiver to associate received RTCP- and RTP packets with a specific
"m=" line, with which the receiver has associated an identification- "m=" line, with which the receiver has associated an identification-
tag, even if those "m=" lines are part of the same RTP session. A tag, even if those "m=" lines are part of the same RTP session. The
media recipient informs the media sender about the identification-tag RTP SDES header extension also ensures that the media recipient gets
associated with an "m=" line through the use of an 'mid' attribute the identification-tag upon receipt of the first decodable media and
[RFC5888]. The media sender then inserts the identification-tag in is able to associate the media with the correct application.
RTCP and RTP packets sent to the media recipient.
A media recipient informs the media sender about the identification-
tag associated with an "m=" line through the use of an 'mid'
attribute [RFC5888]. The media sender then inserts the
identification-tag in RTCP and RTP packets sent to the media
recipient.
NOTE: This text above defines how identification-tags are carried in NOTE: This text above defines how identification-tags are carried in
SDP Offers and Answers. The usage of other signalling protocols for SDP Offers and Answers. The usage of other signalling protocols for
carrying identification-tags is not prevented, but the usage of such carrying identification-tags is not prevented, but the usage of such
protocols is outside the scope of this document. protocols is outside the scope of this document.
[RFC3550] defines general procedures regarding the RTCP transmission [RFC3550] defines general procedures regarding the RTCP transmission
interval. The RTCP MID SDES item SHOULD be sent in the first few interval. The RTCP MID SDES item SHOULD be sent in the first few
RTCP packets sent on joining the session, and SHOULD be sent RTCP packets sent after joining the session, and SHOULD be sent
regularly thereafter. The exact number of RTCP packets in which this regularly thereafter. The exact number of RTCP packets in which this
SDES item is sent is intentionally not specified here, as it will SDES item is sent is intentionally not specified here, as it will
depend on the expected packet loss rate, the RTCP reporting interval, depend on the expected packet loss rate, the RTCP reporting interval,
and the allowable overhead. and the allowable overhead.
The RTP MID header extension SHOULD be included in some RTP packets The RTP SDES header extension for carrying the 'MID' RTCP SDES SHOULD
at the start of the session and whenever the SSRC changes. It might be included in some RTP packets at the start of the session and
also be useful to include the header extension in RTP packets that whenever the SSRC changes. It might also be useful to include the
comprise random access points in the media (e.g., with video header extension in RTP packets that comprise access points in the
I-frames). The exact number of RTP packets in which this header media (e.g., with video I-frames). The exact number of RTP packets
extension is sent is intentionally not specified here, as it will in which this header extension is sent is intentionally not specified
depend on expected packet loss rate and loss patterns, the overhead here, as it will depend on expected packet loss rate and loss
the application can tolerate, and the importance of immediate receipt patterns, the overhead the application can tolerate, and the
of the identification-tag. importance of immediate receipt of the identification-tag.
For robustness purpose, endpoints need to be prepared for situations For robustness purpose, endpoints need to be prepared for situations
where the reception of the identification-tag is delayed, and SHOULD where the reception of the identification-tag is delayed, and SHOULD
NOT terminate sessions in such cases, as the identification-tag is NOT terminate sessions in such cases, as the identification-tag is
likely to arrive soon. likely to arrive soon.
14.2. RTCP MID SDES Item 14.1. RTCP MID SDES Item
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MID=TBD | length | identification-tag ... | MID=TBD | length | identification-tag ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The identification-tag payload is UTF-8 encoded, as in SDP. The identification-tag payload is UTF-8 encoded, as in SDP.
The identification-tag is not zero terminated. The identification-tag is not zero terminated.
[RFC EDITOR NOTE: Please replace TBD with the assigned SDES [RFC EDITOR NOTE: Please replace TBD with the assigned SDES
identifier value.] identifier value.]
14.3. RTP MID Header Extension 14.2. RTP SDES Header Extension For MID
The payload, containing the identification-tag, of the RTP MID header The payload, containing the identification-tag, of the RTP SDES
extension element can be encoded using either the one-byte or two- header extension element can be encoded using either the one-byte or
byte header [RFC5285]. The identification-tag payload is UTF-8 two-byte header [I-D.ietf-avtext-sdes-hdr-ext]. The identification-
encoded, as in SDP. tag payload is UTF-8 encoded, as in SDP.
The identification-tag is not zero terminated. Note, that set of The identification-tag is not zero terminated. Note, that the set of
header extensions included in the packet needs to be padded to the header extensions included in the packet needs to be padded to the
next 32-bit boundary using zero bytes [RFC5285]. next 32-bit boundary using zero bytes [RFC5285].
As the identification-tag is included in either an RTCP SDES item or As the identification-tag is included in either an RTCP SDES item or
an RTP header extension, or both, there should be some consideration an RTP SDES header extension, or both, there should be some
about the packet expansion caused by the identification-tag. To consideration about the packet expansion caused by the
avoid Maximum Transmission Unit (MTU) issues for the RTP packets, the identification-tag. To avoid Maximum Transmission Unit (MTU) issues
header extension's size needs to be taken into account when encoding for the RTP packets, the header extension's size needs to be taken
the media. into account when encoding the media.
It is recommended that the identification-tag is kept short. Due to It is recommended that the identification-tag is kept short. Due to
the properties of the RTP header extension mechanism, when using the the properties of the RTP header extension mechanism, when using the
one-byte header, a tag that is 1-3 bytes will result in that a one-byte header, a tag that is 1-3 bytes will result in a minimal
minimal number of 32-bit words are used for the RTP header extension, number of 32-bit words used for the RTP SDES header extension, in
in case no other header extensions are included at the same time. case no other header extensions are included at the same time. Note,
Note, do take into account that some single characters when UTF-8 do take into account that some single characters when UTF-8 encoded
encoded will result in multiple octets. will result in multiple octets. The identification-tag MUST NOT
contain any user information, and applications SHALL avoid generating
the identification-tag using a pattern that enables application
identification.
15. IANA Considerations 15. IANA Considerations
15.1. New SDES item 15.1. New SDES item
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.] document.]
[RFC EDITOR NOTE: Please replace TBD with the assigned SDES [RFC EDITOR NOTE: Please replace TBD with the assigned SDES
identifier value.] identifier value.]
This document adds the MID SDES item to the IANA "RTP SDES item This document adds the MID SDES item to the IANA "RTP SDES item
types" registry as follows: types" registry as follows:
Value: TBD Value: TBD
Abbrev.: MID Abbrev.: MID
Name: Media Identification Name: Media Identification
Reference: RFCXXXX Reference: RFCXXXX
15.2. New RTP Header Extension URI 15.2. New RTP SDES Header Extension URI
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.] document.]
This document defines a new extension URI in the RTP SDES Compact This document defines a new extension URI in the RTP SDES Compact
Header Extensions sub-registry of the RTP Compact Header Extensions Header Extensions sub-registry of the RTP Compact Header Extensions
registry sub-registry, according to the following data: registry sub-registry, according to the following data:
Extension URI: urn:ietf:params:rtp-hdrext:sdes:mid Extension URI: urn:ietf:params:rtp-hdrext:sdes:mid
Description: Media identification Description: Media identification
skipping to change at page 31, line 5 skipping to change at page 30, line 26
receives the associated SDP answer. receives the associated SDP answer.
15.3. New SDP Attribute 15.3. New SDP Attribute
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.] document.]
This document defines a new SDP media-level attribute, 'bundle-only', This document defines a new SDP media-level attribute, 'bundle-only',
according to the following data: according to the following data:
Attribute name: bundle-only Attribute name: bundle-only
Type of attribute: media Type of attribute: media
Subject to charset: No Subject to charset: No
Purpose: Request a media description to be accepted Purpose: Request a media description to be accepted
in the answer only if kept within a BUNDLE in the answer only if kept within a BUNDLE
group by the answerer. group by the answerer.
Appropriate values: N/A Appropriate values: N/A
Contact name: Christer Holmberg Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX Reference: RFCXXXX
Mux category: NORMAL
15.4. New SDP Group Semantics 15.4. New SDP Group Semantics
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.] document.]
This document registers the following semantics with IANA in the This document registers the following semantics with IANA in the
"Semantics for the "group" SDP Attribute" subregistry (under the "Semantics for the "group" SDP Attribute" subregistry (under the
"Session Description Protocol (SDP) Parameters" registry: "Session Description Protocol (SDP) Parameters" registry:
skipping to change at page 32, line 15 skipping to change at page 31, line 36
17. Examples 17. Examples
17.1. Example: Bundle Address Selection 17.1. Example: Bundle Address Selection
The example below shows: The example below shows:
o An offer, in which the offerer associates a unique address with o An offer, in which the offerer associates a unique address with
each bundled "m=" line within the BUNDLE group. each bundled "m=" line within the BUNDLE group.
o An answer, in which the answerer selects the offerer BUNDLE o An answer, in which the answerer selects the offerer BUNDLE
address, and in which selects its own BUNDLE address (the answerer address, and then selects its own BUNDLE address (the answerer
BUNDLE address) and associates it with each bundled "m=" line BUNDLE address) and associates it with each bundled "m=" line
within the BUNDLE group. 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
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
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
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 10002 RTP/AVP 31 32 m=video 10002 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
SDP Answer (2) SDP Answer (2)
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
s= s=
c=IN IP4 biloxi.example.com c=IN IP4 biloxi.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 20000 RTP/AVP 0 m=audio 20000 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
17.2. Example: BUNDLE Extension Rejected 17.2. Example: BUNDLE Extension Rejected
The example below shows: The example below shows:
o An offer, in which the offerer associates a unique address with o An offer, in which the offerer associates a unique address with
each bundled "m=" line within the BUNDLE group. each bundled "m=" line within the BUNDLE group.
skipping to change at page 35, line 16 skipping to change at page 34, line 16
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
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
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
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 10002 RTP/AVP 31 32 m=video 10002 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
SDP Answer (2) SDP Answer (2)
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
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=rtcp-mux
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=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
17.3. Example: Offerer Adds A Media Description To A BUNDLE Group 17.3. Example: Offerer Adds A Media Description To A BUNDLE Group
The example below shows: The example below shows:
o A subsequent offer (the BUNDLE group has been created as part of a o A subsequent offer (the BUNDLE group has been created as part of a
previous offer/answer transaction), in which the offerer adds a previous offer/answer exchange), in which the offerer adds a new
new "m=" line, represented by the "zen" identification-tag, to a "m=" line, represented by the "zen" identification-tag, to a
previously negotiated BUNDLE group, associates a unique address previously negotiated BUNDLE group, associates a unique address
with the added "m=" line, and associates the previously selected with the added "m=" line, and associates the previously selected
offerer BUNDLE address with each of the other bundled "m=" lines offerer BUNDLE address with each of the other bundled "m=" lines
within the BUNDLE group. within the BUNDLE group.
o An answer, in which the answerer associates the answerer BUNDLE o An answer, in which the answerer associates the answerer BUNDLE
address with each bundled "m=" line (including the newly added address with each bundled "m=" line (including the newly added
"m=" line) within the BUNDLE group. "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 zen a=group:BUNDLE foo bar zen
m=audio 10000 RTP/AVP 0 8 97 m=audio 10000 RTP/AVP 0 8 97
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
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
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 10000 RTP/AVP 31 32 m=video 10000 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 66 m=video 20000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=mid:zen a=mid:zen
a=rtcp-mux
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
SDP Answer (2) SDP Answer (2)
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
s= s=
c=IN IP4 biloxi.example.com c=IN IP4 biloxi.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar zen a=group:BUNDLE foo bar zen
m=audio 20000 RTP/AVP 0 m=audio 20000 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 66 m=video 20000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=mid:zen a=mid:zen
a=rtcp-mux
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
17.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group 17.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group
The example below shows: The example below shows:
o A subsequent offer (the BUNDLE group has been created as part of a o A subsequent offer (the BUNDLE group has been created as part of a
previous offer/answer transaction), in which the offerer moves a previous offer/answer transaction), in which the offerer moves a
bundled "m=" line out of a BUNDLE group, associates a unique bundled "m=" line out of a BUNDLE group, associates a unique
address with the moved "m=" line, and associates the offerer address with the moved "m=" line, and associates the offerer
BUNDLE address with each other bundled "m=" line within the BUNDLE BUNDLE address with each other bundled "m=" line within the BUNDLE
group. group.
o An answer, in which the answerer moves the "m=" line out of the o An answer, in which the answerer moves the "m=" line out of the
BUNDLE group, associates unique address with the moved "m=" line, BUNDLE group, associates a unique address with the moved "m="
and associates the answerer BUNDLE address with each of the line, and associates the answerer BUNDLE address with each of the
remaining bundled "m=" line within the BUNDLE group. remaining 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
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
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
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 10000 RTP/AVP 31 32 m=video 10000 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 50000 RTP/AVP 66 m=video 50000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=mid:zen a=mid:zen
a=rtcp-mux
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
SDP Answer (2) SDP Answer (2)
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
s= s=
c=IN IP4 biloxi.example.com c=IN IP4 biloxi.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 20000 RTP/AVP 0 m=audio 20000 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 60000 RTP/AVP 66 m=video 60000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=mid:zen a=mid:zen
a=rtcp-mux
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
17.5. Example: Offerer Disables A Media Description Within A BUNDLE 17.5. Example: Offerer Disables A Media Description Within A BUNDLE
Group Group
The example below shows: The example below shows:
o A subsequent offer (the BUNDLE group has been created as part of a o A subsequent offer (the BUNDLE group has been created as part of a
previous offer/answer transaction), in which the offerer disables previous offer/answer transaction), in which the offerer disables
a bundled "m=" line within BUNDLE group, assigns a zero port a bundled "m=" line within a BUNDLE group, assigns a zero port
number to the disabled "m=" line, and associates the offerer number to the disabled "m=" line, and associates the offerer
BUNDLE address with each of the other bundled "m=" lines within BUNDLE address with each of the other bundled "m=" lines within
the BUNDLE group. the BUNDLE group.
o An answer, in which the answerer moves the disabled "m=" line out o An answer, in which the answerer moves the disabled "m=" line out
of the BUNDLE group, assigns a zero port value to the disabled of the BUNDLE group, assigns a zero port value to the disabled
"m=" line, and associates the answerer BUNDLE address with each of "m=" line, and associates the answerer BUNDLE address with each of
the remaining bundled "m=" line within the BUNDLE group. the remaining 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
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
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
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 10000 RTP/AVP 31 32 m=video 10000 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000 a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 0 RTP/AVP 66 m=video 0 RTP/AVP 66
a=mid:zen a=mid:zen
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
SDP Answer (2) SDP Answer (2)
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
s= s=
c=IN IP4 biloxi.example.com c=IN IP4 biloxi.example.com
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
m=audio 20000 RTP/AVP 0 m=audio 20000 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 20000 RTP/AVP 32 m=video 20000 RTP/AVP 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
m=video 0 RTP/AVP 66 m=video 0 RTP/AVP 66
a=mid:zen a=mid:zen
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
18. Acknowledgements 18. 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 extension described in this document is Cullen Jennings. The BUNDLE extension 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, Martin Thomson, Flemming Andreasen, Thomas Thanks to Paul Kyzivat, Martin Thomson, Flemming Andreasen, Thomas
Stach, Ari Keranen, Adam Roach, Christian Groves, Roman Shpount, Stach, Ari Keranen, Adam Roach, Christian Groves, Roman Shpount,
Suhas Nandakumar, Nils Ohlmeier, Jens Guballa, Raju Makaraju and Suhas Nandakumar, Nils Ohlmeier, Jens Guballa, Raju Makaraju and
Justin Uberti for reading the text, and providing useful feedback. Justin Uberti for reading the text, and providing useful feedback.
skipping to change at page 40, line 37 skipping to change at page 40, line 9
Thanks to Magnus Westerlund, Colin Perkins and Jonathan Lennox for Thanks to Magnus Westerlund, Colin Perkins and Jonathan Lennox for
providing help and text on the RTP/RTCP procedures. providing help and text on the RTP/RTCP procedures.
Thanks to Spotify for providing music for the countless hours of Thanks to Spotify for providing music for the countless hours of
document editing. document editing.
19. Change Log 19. 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-31
o Editorial changes based on GitHub Pull requests by Martin Thomson:
o - https://github.com/cdh4u/draft-sdp-bundle/pull/2
o - https://github.com/cdh4u/draft-sdp-bundle/pull/1
o Editorial change based on comment from Diederick Huijbers (9th
July 2016).
o Changes based on comments from Flemming Andreasen (21st June
2016):
o - Mux category for SDP bundle-only attribute added.
o - Mux category considerations editorial clarification.
o - Editorial changes.
o RTP SDES extension according to draft-ietf-avtext-sdes-hdr-ext.
o Note whether Design Considerations appendix is to be kept removed:
o - Appendix is kept within document.
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-30 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-30
o Indicating in the Abstract and Introduction that the document o Indicating in the Abstract and Introduction that the document
updates RFC 3264. updates RFC 3264.
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-29 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-29
o Change based on WGLC comment from Colin Perkins. o Change based on WGLC comment from Colin Perkins.
o - Clarify that SSRC can be reused by another source after a delay o - Clarify that SSRC can be reused by another source after a delay
skipping to change at page 48, line 49 skipping to change at page 48, line 40
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, Protocol (SDP) Grouping Framework", RFC 5888,
DOI 10.17487/RFC5888, June 2010, DOI 10.17487/RFC5888, June 2010,
<http://www.rfc-editor.org/info/rfc5888>. <http://www.rfc-editor.org/info/rfc5888>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>. January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[I-D.ietf-ice-rfc5245bis] [I-D.ietf-ice-rfc5245bis]
Keraenen, A., Holmberg, C., and J. Rosenberg, "Interactive Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice- Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-02 (work in progress), June 2016. rfc5245bis-04 (work in progress), June 2016.
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-13
(work in progress), January 2016. (work in progress), June 2016.
[I-D.ietf-mmusic-mux-exclusive] [I-D.ietf-mmusic-mux-exclusive]
Holmberg, C., "Indicating Exclusive Support of RTP/RTCP Holmberg, C., "Indicating Exclusive Support of RTP/RTCP
Multiplexing using SDP", draft-ietf-mmusic-mux- Multiplexing using SDP", draft-ietf-mmusic-mux-
exclusive-07 (work in progress), June 2016. exclusive-10 (work in progress), August 2016.
[I-D.ietf-mmusic-ice-sip-sdp] [I-D.ietf-mmusic-ice-sip-sdp]
Petit-Huguenin, M., Keraenen, A., and S. Nandakumar, Petit-Huguenin, M., Keranen, A., and S. Nandakumar, "Using
"Using Interactive Connectivity Establishment (ICE) with Interactive Connectivity Establishment (ICE) with Session
Session Description Protocol (SDP) offer/answer and Description Protocol (SDP) offer/answer and Session
Session Initiation Protocol (SIP)", draft-ietf-mmusic-ice- Initiation Protocol (SIP)", draft-ietf-mmusic-ice-sip-
sip-sdp-08 (work in progress), March 2016. sdp-10 (work in progress), July 2016.
[I-D.ietf-avtext-sdes-hdr-ext]
Westerlund, M., Burman, B., Even, R., and M. Zanaty, "RTP
Header Extension for RTCP Source Description Items",
draft-ietf-avtext-sdes-hdr-ext-07 (work in progress), June
2016.
20.2. Informative References 20.2. Informative References
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>. <http://www.rfc-editor.org/info/rfc3261>.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
skipping to change at page 50, line 7 skipping to change at page 50, line 7
<http://www.rfc-editor.org/info/rfc7160>. <http://www.rfc-editor.org/info/rfc7160>.
[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-02 (work in progress), January 2015. mmusic-trickle-ice-02 (work in progress), January 2015.
Appendix A. Design Considerations Appendix A. Design Considerations
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 value been whether, in SDP Offers and SDP Answers, the same port value
should be inserted in "m=" lines associated with a BUNDLE group, as should be inserted in "m=" lines associated with a BUNDLE group, as
the purpose of the extension is to negotiate the usage of a single the purpose of the extension is to negotiate the usage of a single
address:port combination for media specified by the "m=" lines. address:port combination for media specified by the "m=" lines.
Issues with both approaches, discussed in the Appendix have been Issues with both approaches, discussed in the Appendix have been
raised. The outcome was to specify a mechanism which uses SDP Offers raised. The outcome was to specify a mechanism which uses SDP Offers
with both different and identical port values. with both different and identical port values.
Below are the primary issues that have been considered when defining Below are the primary issues that have been considered when defining
skipping to change at page 50, line 32 skipping to change at page 50, line 30
o 2) Interoperability with intermediary B2BUA- and proxy entities. o 2) Interoperability with intermediary B2BUA- and proxy entities.
o 3) Time to gather, and the number of, ICE candidates. o 3) Time to gather, and the number of, ICE candidates.
o 4) Different error scenarios, and when they occur. o 4) Different error scenarios, and when they occur.
o 5) SDP Offer/Answer impacts, including usage of port number value o 5) SDP Offer/Answer impacts, including usage of port number value
zero. zero.
NOTE: Before this document is published as an RFC, this A.1. UA Interoperability
Appendix might be removed.
A.2. UA Interoperability
Consider the following SDP Offer/Answer exchange, where Alice sends Consider the following SDP Offer/Answer exchange, where Alice sends
an SDP Offer to Bob: an SDP Offer to Bob:
SDP Offer SDP Offer
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
skipping to change at page 51, line 34 skipping to change at page 51, line 22
m=audio 20000 RTP/AVP 97 m=audio 20000 RTP/AVP 97
a=rtpmap:97 iLBC/8000 a=rtpmap:97 iLBC/8000
m=video 20002 RTP/AVP 97 m=video 20002 RTP/AVP 97
a=rtpmap:97 H261/90000 a=rtpmap:97 H261/90000
RFC 4961 specifies a way of doing symmetric RTP but that is an a RFC 4961 specifies a way of doing symmetric RTP but that is an a
later invention to RTP and Bob can not assume that Alice supports RFC later invention to RTP and Bob can not assume that Alice supports RFC
4961. This means that Alice may be sending RTP from a different port 4961. This means that Alice may be sending RTP from a different port
than 10000 or 10002 - some implementation simply send the RTP from an than 10000 or 10002 - some implementation simply send the RTP from an
ephemeral port. When Bob's endpoint receives an RTP packet, the only ephemeral port. When Bob's endpoint receives an RTP packet, the only
way that Bob know if it should be passed to the video or audio codec way that Bob knows if it should be passed to the video or audio codec
is by looking at the port it was received on. This lead some SDP is by looking at the port it was received on. This lead some SDP
implementations to use the fact that each "m=" line had a different implementations to use the fact that each "m=" line had a different
port number to use that port number as an index to find the correct m port number to use that port number as an index to find the correct m
line in the SDP. As a result, some implementations that do support line in the SDP. As a result, some implementations that do support
symmetric RTP and ICE still use a SDP data structure where SDP with symmetric RTP and ICE still use a SDP data structure where SDP with
"m=" lines with the same port such as: "m=" lines with the same port such as:
SDP Offer SDP Offer
v=0 v=0
skipping to change at page 52, line 20 skipping to change at page 52, line 5
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
t=0 0 t=0 0
m=audio 10000 RTP/AVP 97 m=audio 10000 RTP/AVP 97
a=rtpmap:97 iLBC/8000 a=rtpmap:97 iLBC/8000
m=video 10000 RTP/AVP 98 m=video 10000 RTP/AVP 98
a=rtpmap:98 H261/90000 a=rtpmap:98 H261/90000
will result in the second "m=" line being considered an SDP error will result in the second "m=" line being considered an SDP error
because it has the same port as the first line. because it has the same port as the first line.
A.3. Usage of port number value zero A.2. Usage of port number value zero
In an SDP Offer or SDP Answer, the media specified by an "m=" line In an SDP Offer or SDP Answer, the media specified by an "m=" line
can be disabled/rejected by setting the port number value to zero. can be disabled/rejected by setting the port number value to zero.
This is different from e.g. using the SDP direction attributes, where This is different from e.g., using the SDP direction attributes,
RTCP traffic will continue even if the SDP "inactive" attribute is where RTCP traffic will continue even if the SDP "inactive" attribute
indicated for the associated "m=" line. is indicated for the associated "m=" line.
If each "m=" line associated with a BUNDLE group would contain If each "m=" line associated with a BUNDLE group would contain
different port values, and one of those port values would be used for different port values, and one of those port values would be used for
a BUNDLE address associated with the BUNDLE group, problems would a BUNDLE address associated with the BUNDLE group, problems would
occur if an endpoint wants to disable/reject the "m=" line associated occur if an endpoint wants to disable/reject the "m=" line associated
with that port, by setting the port value to zero. After that, no with that port, by setting the port value to zero. After that, no
"m=" line would contain the port value which is used for the BUNDLE "m=" line would contain the port value which is used for the BUNDLE
address. In addition, it is unclear what would happen to the ICE address. In addition, it is unclear what would happen to the ICE
candidates associated with the "m=" line, as they are also used for candidates associated with the "m=" line, as they are also used for
the BUNDLE address. the BUNDLE address.
A.4. B2BUA And Proxy Interoperability A.3. B2BUA And Proxy Interoperability
Some back to back user agents may be configured in a mode where if Some back to back user agents may be configured in a mode where if
the incoming call leg contains an SDP attribute the B2BUA does not the incoming call leg contains an SDP attribute the B2BUA does not
understand, the B2BUS still generates that SDP attribute in the Offer understand, the B2BUA still generates that SDP attribute in the Offer
for the outgoing call leg. Consider an B2BUA that did not understand for the outgoing call leg. Consider a B2BUA that did not understand
the SDP "rtcp" attribute, defined in RFC 3605, yet acted this way. the SDP "rtcp" attribute, defined in RFC 3605, yet acted this way.
Further assume that the B2BUA was configured to tear down any call Further assume that the B2BUA was configured to tear down any call
where it did not see any RTCP for 5 minutes. In this cases, if the where it did not see any RTCP for 5 minutes. In this case, if the
B2BUA received an Offer like: B2BUA received an Offer like:
SDP Offer SDP Offer
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
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=rtcp:53020 a=rtcp:53020
It would be looking for RTCP on port 49172 but would not see any It would be looking for RTCP on port 49172 but would not see any
because the RTCP would be on port 53020 and after five minutes, it because the RTCP would be on port 53020 and after five minutes, it
would tear down the call. Similarly, an SBC that did not understand would tear down the call. Similarly, a B2BUA that did not understand
BUNDLE yet put BUNDLE in it's offer may be looking for media on the BUNDLE yet put BUNDLE in it's offer may be looking for media on the
wrong port and tear down the call. It is worth noting that a B2BUA wrong port and tear down the call. It is worth noting that a B2BUA
that generated an Offer with capabilities it does not understand is that generated an Offer with capabilities it does not understand is
not compliant with the specifications. not compliant with the specifications.
A.4.1. Traffic Policing A.3.1. Traffic Policing
Sometimes intermediaries do not act as B2BUA, in the sense that they Sometimes intermediaries do not act as B2BUA, in the sense that they
don't modify SDP bodies, nor do they terminate SIP dialogs. Still, don't modify SDP bodies, nor do they terminate SIP dialogs. Still,
however, they may use SDP information (e.g. IP address and port) in however, they may use SDP information (e.g., IP address and port) in
order to control traffic gating functions, and to set traffic order to control traffic gating functions, and to set traffic
policing rules. There might be rules which will trigger a session to policing rules. There might be rules which will trigger a session to
be terminated in case media is not sent or received on the ports be terminated in case media is not sent or received on the ports
retrieved from the SDP. This typically occurs once the session is retrieved from the SDP. This typically occurs once the session is
already established and ongoing. already established and ongoing.
A.4.2. Bandwidth Allocation A.3.2. Bandwidth Allocation
Sometimes intermediaries do not act as B2BUA, in the sense that they Sometimes intermediaries do not act as B2BUA, in the sense that they
don't modify SDP bodies, nor do they terminate SIP dialogs. Still, don't modify SDP bodies, nor do they terminate SIP dialogs. Still,
however, they may use SDP information (e.g. codecs and media types) however, they may use SDP information (e.g., codecs and media types)
in order to control bandwidth allocation functions. The bandwidth in order to control bandwidth allocation functions. The bandwidth
allocation is done per "m=" line, which means that it might not be allocation is done per "m=" line, which means that it might not be
enough if media specified by all "m=" lines try to use that enough if media specified by all "m=" lines try to use that
bandwidth. That may either simply lead to bad user experience, or to bandwidth. That may either simply lead to bad user experience, or to
termination of the call. termination of the call.
A.5. Candidate Gathering A.4. Candidate Gathering
When using ICE, an candidate needs to be gathered for each port.
This takes approximately 20 ms extra for each extra "m=" line due to
the NAT pacing requirements. All of this gather can be overlapped
with other things while the page is loading to minimize the impact.
If the client only wants to generate TURN or STUN ICE candidates for When using ICE, a candidate needs to be gathered for each port. This
one of the "m=" lines and then use trickle ICE takes approximately 20 ms extra for each extra "m=" line due to the
NAT pacing requirements. All of this gather can be overlapped with
other things while for exampe a web-page is loading to minimize the
impact. If the client only wants to generate TURN or STUN ICE
candidates for one of the "m=" lines and then use trickle ICE
[I-D.ietf-mmusic-trickle-ice] to get the non host ICE candidates for [I-D.ietf-mmusic-trickle-ice] to get the non host ICE candidates for
the rest of the "m=" lines, it MAY do that and will not need any the rest of the "m=" lines, it MAY do that and will not need any
additional gathering time. additional gathering time.
Some people have suggested a TURN extension to get a bunch of TURN Some people have suggested a TURN extension to get a bunch of TURN
allocation at once. This would only provide a single STUN result so allocations at once. This would only provide a single STUN result so
in cases where the other end did not support BUNDLE, may cause more in cases where the other end did not support BUNDLE, may cause more
use of the TURN server but would be quick in the cases where both use of the TURN server but would be quick in the cases where both
sides supported BUNDLE and would fall back to a successful call in sides supported BUNDLE and would fall back to a successful call in
the other cases. the other cases.
Authors' Addresses Authors' Addresses
Christer Holmberg Christer Holmberg
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
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