draft-ietf-mmusic-sdp-bundle-negotiation-43.txt   draft-ietf-mmusic-sdp-bundle-negotiation-44.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: June 11, 2018 C. Jennings Expires: June 16, 2018 C. Jennings
Cisco Cisco
December 8, 2017 December 13, 2017
Negotiating Media Multiplexing Using the Session Description Protocol Negotiating Media Multiplexing Using the Session Description Protocol
(SDP) (SDP)
draft-ietf-mmusic-sdp-bundle-negotiation-43.txt draft-ietf-mmusic-sdp-bundle-negotiation-44.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 transport (5-tuple) for sending and receiving media described single transport (5-tuple) for sending and receiving media described
by multiple SDP media descriptions ("m=" sections). Such transport by multiple SDP media descriptions ("m=" sections). Such transport
is referred to as a BUNDLE transport, and the media is referred to as is referred to as a BUNDLE transport, and the media is referred to as
bundled media. The "m=" sections that use the BUNDLE transport form bundled media. The "m=" sections that use the BUNDLE transport form
a BUNDLE group. a BUNDLE group.
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 assigning a zero port specification also updates RFC 3264, to allow assigning a zero port
value to a "m= section without meaning that the media described by value to a "m=" section without meaning that the media described by
the "m=" section is disabled or rejected. the "m=" section is disabled or rejected.
When RTP-based media is used, there are multiple ways to correlate When RTP-based media is used, there are multiple ways to correlate
bundled RTP packets with the appropriate "m=" section. This bundled RTP packets with the appropriate "m=" section. This
specification defines a new Real-time Transport Protocol (RTP) source specification defines a new Real-time Transport Control Protocol
description (SDES) item and a new RTP header extension that provides (RTCP) source description (SDES) item and a new RTP header extension
an additional way to do this correlation by using them to carry a that provides an additional way to do this correlation by using them
value that associates the RTP/RTCP packets with a specific "m=" to carry a value that associates the RTP/RTCP packets with a specific
section. "m=" section.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://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 June 11, 2018. This Internet-Draft will expire on June 16, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
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carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License. described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this 10, 2008. The person(s) controlling the copyright in some of this
skipping to change at page 3, line 4 skipping to change at page 3, line 4
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 . . . . . . . . . . . . . . . 9
7.1. Connection Data (c=) . . . . . . . . . . . . . . . . . . 9 7.1. Connection Data (c=) . . . . . . . . . . . . . . . . . . 9
7.2. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . . . 9 7.2. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . . . 9
8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 9 8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 9
8.1. Mux Category Considerations . . . . . . . . . . . . . . . 10 8.1. Mux Category Considerations . . . . . . . . . . . . . . . 10
8.2. Generating the Initial SDP Offer . . . . . . . . . . . . 11 8.2. Generating the Initial SDP Offer . . . . . . . . . . . . 11
8.2.1. Suggesting the offerer BUNDLE address . . . . . . . . 11 8.2.1. Suggesting the Offerer BUNDLE Address . . . . . . . . 12
8.2.2. Example: Initial SDP Offer . . . . . . . . . . . . . 12 8.2.2. Example: Initial SDP Offer . . . . . . . . . . . . . 12
8.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 12 8.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 13
8.3.1. Answerer Selection of Offerer Bundle Address . . . . 13 8.3.1. Answerer Selection of Offerer BUNDLE Address . . . . 14
8.3.2. Answerer Selection of Answerer BUNDLE Address . . . . 14 8.3.2. Answerer Selection of Answerer BUNDLE Address . . . . 15
8.3.3. Moving A Media Description Out Of A BUNDLE Group . . 14 8.3.3. Moving A Media Description Out Of A BUNDLE Group . . 15
8.3.4. Rejecting A Media Description In A BUNDLE Group . . . 15 8.3.4. Rejecting a Media Description in a BUNDLE Group . . . 16
8.3.5. Example: SDP Answer . . . . . . . . . . . . . . . . . 16 8.3.5. Example: SDP Answer . . . . . . . . . . . . . . . . . 17
8.4. Offerer Processing of the SDP Answer . . . . . . . . . . 17 8.4. Offerer Processing of the SDP Answer . . . . . . . . . . 17
8.5. Modifying the Session . . . . . . . . . . . . . . . . . . 17 8.5. Modifying the Session . . . . . . . . . . . . . . . . . . 18
8.5.1. Suggesting a new offerer BUNDLE address . . . . . . . 17 8.5.1. Suggesting a New Offerer BUNDLE Address . . . . . . . 18
8.5.2. Adding a media description to a BUNDLE group . . . . 18 8.5.2. Adding a Media Description to a BUNDLE group . . . . 18
8.5.3. Moving A Media Description Out Of A BUNDLE Group . . 18 8.5.3. Moving a Media Description Out of a BUNDLE Group . . 19
8.5.4. Disabling A Media Description In A BUNDLE Group . . . 19 8.5.4. Disabling a Media Description in a BUNDLE Group . . . 19
9. Protocol Identification . . . . . . . . . . . . . . . . . . . 19 9. Protocol Identification . . . . . . . . . . . . . . . . . . . 20
9.1. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 20 9.1. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 20
10. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 20 10. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 21
10.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 20 10.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 21
10.1.1. Payload Type (PT) Value Reuse . . . . . . . . . . . 21 10.1.1. Payload Type (PT) Value Reuse . . . . . . . . . . . 22
10.2. Associating RTP/RTCP Streams With Correct SDP Media 10.2. Associating RTP/RTCP Streams with Correct SDP Media
Description . . . . . . . . . . . . . . . . . . . . . . 21 Description . . . . . . . . . . . . . . . . . . . . . . 22
10.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . 27 10.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . 28
10.3.1. SDP Offer/Answer Procedures . . . . . . . . . . . . 27 10.3.1. SDP Offer/Answer Procedures . . . . . . . . . . . . 28
11. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 29 11. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 30
11.1. SDP Offer/Answer Procedures . . . . . . . . . . . . . . 30 11.1. SDP Offer/Answer Procedures . . . . . . . . . . . . . . 31
12. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 31 12. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 31
13. RTP Header Extensions Consideration . . . . . . . . . . . . . 31 13. RTP Header Extensions Consideration . . . . . . . . . . . . . 32
14. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 32 14. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 32
14.1. Original text of section 5.1 (2nd paragraph) of RFC 3264 32 14.1. Original text of section 5.1 (2nd paragraph) of RFC 3264 33
14.2. New text replacing section 5.1 (2nd paragraph) of RFC 14.2. New text replacing section 5.1 (2nd paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 33
14.3. Original text of section 6 (4th paragraph) of RFC 3264 . 33 14.3. Original text of section 6 (4th paragraph) of RFC 3264 . 33
14.4. New text replacing section 6 (4th paragraph) of RFC 3264 33 14.4. New text replacing section 6 (4th paragraph) of RFC 3264 34
14.5. Original text of section 8.2 (2nd paragraph) of RFC 3264 33 14.5. Original text of section 8.2 (2nd paragraph) of RFC 3264 34
14.6. New text replacing section 8.2 (2nd paragraph) of RFC 14.6. New text replacing section 8.2 (2nd paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 34
14.7. Original text of section 8.4 (6th paragraph) of RFC 3264 33 14.7. Original text of section 8.4 (6th paragraph) of RFC 3264 34
14.8. New text replacing section 8.4 (6th paragraph) of RFC 14.8. New text replacing section 8.4 (6th paragraph) of RFC
3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 34
15. RTP/RTCP extensions for identification-tag transport . . . . 34 15. RTP/RTCP extensions for identification-tag transport . . . . 35
15.1. RTCP MID SDES Item . . . . . . . . . . . . . . . . . . . 35 15.1. RTCP MID SDES Item . . . . . . . . . . . . . . . . . . . 36
15.2. RTP SDES Header Extension For MID . . . . . . . . . . . 35 15.2. RTP SDES Header Extension For MID . . . . . . . . . . . 36
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
16.1. New SDES item . . . . . . . . . . . . . . . . . . . . . 36 16.1. New SDES item . . . . . . . . . . . . . . . . . . . . . 37
16.2. New RTP SDES Header Extension URI . . . . . . . . . . . 37 16.2. New RTP SDES Header Extension URI . . . . . . . . . . . 37
16.3. New SDP Attribute . . . . . . . . . . . . . . . . . . . 37 16.3. New SDP Attribute . . . . . . . . . . . . . . . . . . . 38
16.4. New SDP Group Semantics . . . . . . . . . . . . . . . . 38 16.4. New SDP Group Semantics . . . . . . . . . . . . . . . . 38
17. Security Considerations . . . . . . . . . . . . . . . . . . . 38 17. Security Considerations . . . . . . . . . . . . . . . . . . . 39
18. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 39 18. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 40
18.1. Example: Bundle Address Selection . . . . . . . . . . . 39 18.1. Example: Bundle Address Selection . . . . . . . . . . . 40
18.2. Example: BUNDLE Extension Rejected . . . . . . . . . . . 41 18.2. Example: BUNDLE Extension Rejected . . . . . . . . . . . 42
18.3. Example: Offerer Adds A Media Description To A BUNDLE 18.3. Example: Offerer Adds a Media Description to a BUNDLE
Group . . . . . . . . . . . . . . . . . . . . . . . . . 42 Group . . . . . . . . . . . . . . . . . . . . . . . . . 43
18.4. Example: Offerer Moves A Media Description Out Of A 18.4. Example: Offerer Moves a Media Description Out of a
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 44 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 45
18.5. Example: Offerer Disables A Media Description Within A 18.5. Example: Offerer Disables a Media Description Within a
BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 46 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 47
19. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 47 19. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48
20. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 48 20. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 49
21. References . . . . . . . . . . . . . . . . . . . . . . . . . 58 21. References . . . . . . . . . . . . . . . . . . . . . . . . . 59
21.1. Normative References . . . . . . . . . . . . . . . . . . 58 21.1. Normative References . . . . . . . . . . . . . . . . . . 59
21.2. Informative References . . . . . . . . . . . . . . . . . 60 21.2. Informative References . . . . . . . . . . . . . . . . . 61
Appendix A. Design Considerations . . . . . . . . . . . . . . . 61 Appendix A. Design Considerations . . . . . . . . . . . . . . . 62
A.1. UA Interoperability . . . . . . . . . . . . . . . . . . . 62 A.1. UA Interoperability . . . . . . . . . . . . . . . . . . . 63
A.2. Usage of port number value zero . . . . . . . . . . . . . 63 A.2. Usage of Port Number Value Zero . . . . . . . . . . . . . 64
A.3. B2BUA And Proxy Interoperability . . . . . . . . . . . . 64 A.3. B2BUA And Proxy Interoperability . . . . . . . . . . . . 65
A.3.1. Traffic Policing . . . . . . . . . . . . . . . . . . 64 A.3.1. Traffic Policing . . . . . . . . . . . . . . . . . . 65
A.3.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 64 A.3.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 65
A.4. Candidate Gathering . . . . . . . . . . . . . . . . . . . 65 A.4. Candidate Gathering . . . . . . . . . . . . . . . . . . . 66
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 66
1. Introduction 1. Introduction
When multimedia communications are established, each transport When multimedia communications are established, each transport
(5-tuple) reserved for an individual media stream consume additional (5-tuple) reserved for an individual media stream consume additional
resources (especially when Interactive Connectivity Establishment resources (especially when Interactive Connectivity Establishment
(ICE) [I-D.ietf-ice-rfc5245bis] is used). For this reason, it is (ICE) [I-D.ietf-ice-rfc5245bis] is used). For this reason, it is
attractive to use a single transport for multiple media streams. attractive to use a single transport for multiple media streams.
This specification defines a way to use a single transport (BUNDLE This specification defines a way to use a single transport (BUNDLE
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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
Session Description Protocol (SDP) Offer/Answer mechanism [RFC3264] Session Description Protocol (SDP) Offer/Answer mechanism [RFC3264]
to negotiate which "m=" sections will become part of a BUNDLE group. to negotiate which "m=" sections will become part of a BUNDLE group.
Within a BUNDLE group, each "m=" section will use a BUNDLE transport Within a BUNDLE group, each "m=" section will use a BUNDLE transport
for sending and receiving bundled media. for sending and receiving bundled media.
Within a BUNDLE group, each endpoint uses a single address:port Within a BUNDLE group, each endpoint uses a single address:port
combination for sending and receiving bundled media. The combination for sending and receiving bundled media. The
address:port combination is referred to as BUNDLE address. In address:port combination is referred to as the BUNDLE address. In
addition to negotiating the BUNDLE group, the offerer and answerer addition to negotiating the BUNDLE group, the offerer and answerer
[RFC3264] use the BUNDLE extension to negotiate the BUNDLE addresses, [RFC3264] use the BUNDLE extension to negotiate the BUNDLE addresses,
one for the offerer (offerer BUNDLE address) and one for the answerer one for the offerer (offerer BUNDLE address) and one for the answerer
(answerer BUNDLE address). Once the offerer and the answerer have (answerer BUNDLE address). Once the offerer and the answerer have
negotiated the BUNDLE addresses, and a BUNDLE group has been formed, negotiated the BUNDLE addresses, and a BUNDLE group has been formed,
they assign their respective BUNDLE address to each "m=" section they assign their respective BUNDLE address to each "m=" section
within the BUNDLE group. The endpoints then use the BUNDLE addresses within the BUNDLE group. The endpoints then use the BUNDLE addresses
for sending and receiving the bundled media associated with the for sending and receiving the bundled media associated with the
BUNDLE group. BUNDLE group.
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SDP bodies can contain multiple BUNDLE groups. A given BUNDLE SDP bodies can contain multiple BUNDLE groups. A given BUNDLE
address MUST only be associated with a single BUNDLE group. The address MUST only be associated with a single BUNDLE group. The
procedures in this specification apply independently to a given procedures in this specification apply independently to a given
BUNDLE group. All RTP based media flows described by a single BUNDLE BUNDLE group. All RTP based media flows described by a single BUNDLE
group belong to a single RTP session [RFC3550]. group belong to a single RTP session [RFC3550].
The BUNDLE extension is backward compatible. Endpoints that do not The BUNDLE extension is backward compatible. Endpoints that do not
support the extension are expected to generate offers and answers support the extension are expected to generate offers and answers
without an SDP 'group:BUNDLE' attribute, and are expected to assign a without an SDP 'group:BUNDLE' attribute, and are expected to assign a
unique address to each "m=" section within an offer and answer, unique address to each "m=" section within an offer and answer,
according to the procedures in [RFC4566] and [RFC3264] according to the procedures in [RFC4566] and [RFC3264].
2. Terminology 2. Terminology
"m=" section: SDP bodies contain one or more media descriptions, "m=" section: SDP bodies contain one or more media descriptions,
referred to as "m=" sections. Each "m=" section is represented by an referred to as "m=" sections. Each "m=" section is represented by an
SDP "m=" line, and zero or more SDP attributes associated with the SDP "m=" line, and zero or more SDP attributes associated with the
"m=" line. An local address:port combination is assigned to each "m=" line. A local address:port combination is assigned to each "m="
"m=" section. section.
5-tuple: A collection of the following values: source address, source 5-tuple: A collection of the following values: source address, source
port, destination address, destination port, and transport-layer port, destination address, destination port, and transport-layer
protocol. protocol.
Unique address: An address:port combination that is assigned to only Unique address: An address:port combination that is assigned to only
one "m=" section in an offer or answer. one "m=" section in an offer or answer.
Offerer BUNDLE-tag: The first identification-tag in a given SDP Offerer BUNDLE-tag: The first identification-tag in a given SDP
'group:BUNDLE' attribute identification-tag list in an offer. 'group:BUNDLE' attribute identification-tag list in an offer.
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offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of
scope of this document, and is thus undefined. scope of this document, and is thus undefined.
5. SDP Grouping Framework BUNDLE Extension 5. SDP Grouping Framework BUNDLE Extension
This section defines a new SDP Grouping Framework [RFC5888] This section defines a new SDP Grouping Framework [RFC5888]
extension, 'BUNDLE'. The BUNDLE extension can be used with the SDP extension, 'BUNDLE'. The BUNDLE extension can be used with the SDP
Offer/Answer mechanism to negotiate a set of "m=" sections that will Offer/Answer mechanism to negotiate a set of "m=" sections that will
become part of a BUNDLE group. Within a BUNDLE group, each "m=" become part of a BUNDLE group. Within a BUNDLE group, each "m="
section will use a BUNDLE transport for sending and receiving bundled section will use a BUNDLE transport for sending and receiving bundled
media. Each endpoint use a single address:port combination for media. Each endpoint uses a single address:port combination for
sending receiving the bundled media. sending and receiving the bundled media.
The BUNDLE extension is indicated using an SDP 'group' attribute with The BUNDLE extension is indicated using an SDP 'group' attribute with
a "BUNDLE" semantics value [RFC5888]. An identification-tag is a "BUNDLE" semantics value [RFC5888]. An identification-tag is
assigned to each bundled "m=" section, and each identification-tag is assigned to each bundled "m=" section, and each identification-tag is
listed in the SDP 'group:BUNDLE' attribute identification-tag list. listed in the SDP 'group:BUNDLE' attribute identification-tag list.
Each "m=" section whose identification-tag is listed in the Each "m=" section whose identification-tag is listed in the
identification-tag list is associated with a given BUNDLE group. identification-tag list is associated with a given BUNDLE group.
SDP bodies can contain multiple BUNDLE groups. Any given bundled SDP bodies can contain multiple BUNDLE groups. Any given bundled
"m=" section MUST NOT be associated with more than one BUNDLE group "m=" section MUST NOT be associated with more than one BUNDLE group
skipping to change at page 8, line 44 skipping to change at page 8, line 44
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=" section, the offerer can extension always rejects a bundled "m=" section, the offerer can
assign a zero port value to the "m=" section. According to [RFC3264] assign a zero port value to the "m=" section. According to [RFC3264]
an answerer will reject such "m=" section. By including an SDP an answerer will reject such an "m=" section. By including an SDP
'bundle-only' attribute in such "m=" section, the offerer can request 'bundle-only' attribute in such an "m=" section, the offerer can
that the answerer accepts the "m=" section if the answerer supports request that the answerer accepts the "m=" section if the answerer
the Bundle extension, and if the answerer keeps the "m=" section supports the BUNDLE extension, and if the answerer keeps the "m="
within the associated BUNDLE group. section within the associated BUNDLE group.
Once the offerer and answerer BUNDLE addresses have been selected, an Once the offerer and answerer BUNDLE addresses have been selected, an
offerer and answerer only assigns the BUNDLE address to one bundled offerer and answerer only assign the BUNDLE address to one bundled
"m=" section. To every other bundled "m=" section the offerer and "m=" section. The offerer and answerer assign a zero port value and
answerer assigns a zero port value and includes an SDP 'bundle-only' includes an SDP 'bundle-only' attribute to every other bundled "m="
attribute. section.
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=" section with a zero port value, within an offer or bundled "m=" section with a zero port value. Other usage is
answer. Other usage is unspecified. 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
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 how to calculate
and attribute values have been assigned to each bundled "m=" section, a value for the whole BUNDLE group, when parameter and attribute
how to calculate a value for the whole BUNDLE group. values have been assigned to each bundled "m=" section.
7.1. 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="
section MUST be 'IN'. section 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="
section MUST be 'IP4' or 'IP6'. The same value MUST be associated section MUST be 'IP4' or 'IP6'. The same value MUST be associated
with each "m=" section. with each "m=" section.
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.
7.2. 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 associating the SDP in [I-D.ietf-mmusic-sdp-mux-attributes] for associating the SDP
bandwidth (b=) line with bundled "m=" section. bandwidth (b=) line with bundled "m=" sections.
8. SDP Offer/Answer Procedures 8. SDP Offer/Answer Procedures
This section describes the SDP Offer/Answer [RFC3264] procedures for: This section describes the SDP Offer/Answer [RFC3264] procedures for:
o Negotiating a BUNDLE group; and o Negotiating 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
skipping to change at page 10, line 35 skipping to change at page 10, line 35
[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.
8.1. Mux Category Considerations 8.1. Mux Category Considerations
When a BUNDLE group is initially negotiated, and a unique address is When a BUNDLE group is initially negotiated, and a unique address is
assigned to each bundled "m=" section (excluding any bundle-only "m=" assigned to each bundled "m=" section (excluding any bundle-only "m="
section) in the initial offer Section 8.2, IDENTICAL and TRANSPORT section) in the initial offer [Section 8.2], IDENTICAL and TRANSPORT
mux category SDP attributes MUST explicitly included in each bundled mux category SDP attributes MUST explicitly be included in each
"m=" section (excluding any bundle-only "m=" secctions). bundled "m=" section (excluding any bundle-only "m=" sections).
When an offerer or answerer includes SDP attributes in bundled "m=" When an offerer or answerer includes SDP attributes in bundled "m="
sections within a BUNDLE group for which the offerer and answerer sections within a BUNDLE group for which the offerer and answerer
BUNDLE addresses have been selected, IDENTICAL and TRANSPORT mux BUNDLE addresses have been selected, IDENTICAL and TRANSPORT mux
category SDP attributes [I-D.ietf-mmusic-sdp-mux-attributes] are only category SDP attributes [I-D.ietf-mmusic-sdp-mux-attributes] are only
included in the "m=" section represented by the BUNDLE-tag in the included in the "m=" section represented by the BUNDLE-tag in the
offer or answer. The SDP attribute values are implicitly applied to offer or answer. The SDP attribute values are implicitly applied to
each bundled "m=" section (including any bundle-only "m=" section). each bundled "m=" section (including any bundle-only "m=" section).
The offerer and answerer MUST NOT include such SDP attributes in any The offerer and answerer MUST NOT include such SDP attributes in any
other bundled "m=" section. other bundled "m=" section.
skipping to change at page 11, line 12 skipping to change at page 11, line 12
'rtcp-mux-only' attributes only apply to "m=" sections describing 'rtcp-mux-only' attributes only apply to "m=" sections describing
RTP-based media. However, as described in Section 8.1, there are RTP-based media. However, as described in Section 8.1, there are
cases where IDENTICAL and TRANSPORT mux category SDP attributes are cases where IDENTICAL and TRANSPORT mux category SDP attributes are
only included in the "m=" sections represented by the BUNDLE-tag. only included in the "m=" sections represented by the BUNDLE-tag.
That means that media-specific IDENTICAL and TRANSPORT mux category That means that media-specific IDENTICAL and TRANSPORT mux category
attributes can be included in an "m=" section associated with another attributes can be included in an "m=" section associated with another
type of media. type of media.
8.2. Generating the Initial SDP Offer 8.2. Generating the Initial SDP Offer
When an offerer generates an initial offer, in order to negotiate a When an offerer generates an initial offer, to negotiate a BUNDLE
BUNDLE group, it MUST: group, it MUST:
o Assign a unique address to each "m=" section within the offer, o Assign a unique address to each "m=" section within the offer,
following the procedures in [RFC3264], excluding any bundle-only following the procedures in [RFC3264], excluding any bundle-only
"m=" sections (see below); and "m=" sections (see below); and
o Include an SDP 'group:BUNDLE' attribute in the offer; and o Include an SDP 'group:BUNDLE' attribute in the offer; and
o Place the identification-tag of each bundled "m=" section in the o Place the identification-tag of each bundled "m=" section in the
SDP 'group:BUNDLE' attribute identification-tag list; and SDP 'group:BUNDLE' attribute identification-tag list; and
skipping to change at page 11, line 41 skipping to change at page 11, line 41
o Include an SDP 'bundle-only' attribute [Section 8.2.1] in the "m=" o Include an SDP 'bundle-only' attribute [Section 8.2.1] in the "m="
secction; and secction; and
o Assign a zero port value to the "m=" section. o Assign a zero port value to the "m=" section.
NOTE: If the offerer assigns a zero port value to an "m=" section, NOTE: If the offerer assigns a zero port value to an "m=" section,
but does not include an SDP 'bundle-only' attribute in the "m=" but does not include an SDP 'bundle-only' attribute in the "m="
section, it is an indication that the offerer wants to disable the section, it is an indication that the offerer wants to disable the
"m=" section [Section 8.5.4]. "m=" section [Section 8.5.4].
[Section 18.1] shows an example of an initial offer. NOTE: If the offerer assigns unique addresses to multiple bundled
"m=" sections, the offerer needs to be prepared to receive bundled
media on each unique address, until it receives the associated answer
and finds out which address:port combination has been selected as the
offerer BUNDLE-address.
8.2.1. Suggesting the offerer BUNDLE address [Section 8.2.2] and [Section 18.1] show an example of an initial
offer.
8.2.1. Suggesting the Offerer BUNDLE Address
In the offer, the address:port combination assigned to the "m=" In the offer, the address:port combination assigned to the "m="
section represented by the offerer BUNDLE-tag indicates offerer section represented by the offerer BUNDLE-tag indicates the offerer
BUNDLE address, i.e., the address:port combination that the offerer BUNDLE address, i.e., the address:port combination that the offerer
suggests for sending and receiving bundled media. suggests for sending and receiving bundled media.
The offerer BUNDLE-tag MUST NOT represent a bundle-only "m=" section. The offerer BUNDLE-tag MUST NOT represent a bundle-only "m=" section.
Hence, the offer MUST contain at least one bundle "m=" section with a Hence, the offer MUST contain at least one bundled "m=" section with
unique address (and a non-zero port value). a unique address (and a non-zero port value).
It is RECOMMENDED that the offerer assigns the suggested offerer
BUNDLE address to a bundled "m=" section that the offerer assumes it
is unlikely that the answerer will reject, or move out of the BUNDLE
group. How such assumption is made is outside the scope of this
document.
8.2.2. Example: Initial SDP Offer 8.2.2. Example: Initial SDP Offer
The example shows an initial SDP offer. The offer includes two "m=" The example shows an initial SDP offer. The offer includes two "m="
section in the SDP, and suggests that both are included in a BUNDLE sections in the SDP, and suggests that both are included in a BUNDLE
group. The audio "m=" section is associated with the offerer BUNDLE- group. The audio "m=" section is represented by the offerer BUNDLE-
tag (placed first in the SDP group:BUNDLE attribute identification-id tag (placed first in the SDP group:BUNDLE attribute identification-id
list). list).
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
skipping to change at page 12, line 36 skipping to change at page 13, line 24
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=rtcp-mux 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
8.3. Generating the SDP Answer 8.3. 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 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:
skipping to change at page 13, line 16 skipping to change at page 13, line 50
group, unless the offerer requested the "m=" section to be within group, unless the offerer requested the "m=" section to be within
that BUNDLE group in the corresponding offer. that BUNDLE group in the corresponding offer.
o If the answer contains multiple BUNDLE groups, the answerer MUST o If the answer contains multiple BUNDLE groups, the answerer MUST
NOT move an "m=" section from one BUNDLE group to another. NOT move an "m=" section from one BUNDLE group to another.
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 8.3.1]; 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 8.3.2].
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=" section within a BUNDLE If the answerer does not want to keep an "m=" section within a BUNDLE
group, it MUST: group, it MUST:
o Move the "m=" section out of the BUNDLE group [Section 8.3.3]; or o Move the "m=" section out of the BUNDLE group [Section 8.3.3]; or
o Reject the "m=" section [Section 8.3.4]; o Reject the "m=" section [Section 8.3.4].
When the answerer creates the answer, it selects the offerer BUNDLE When the answerer creates the answer, it selects the offerer BUNDLE
address [Section 8.3.1] and the answerer BUNDLE address address [Section 8.3.1] and the answerer BUNDLE address
[Section 8.3.2]. The answerer then assigns the answerer BUNDLE [Section 8.3.2]. The answerer then assigns the answerer BUNDLE
address to the bundled "m=" section represented by the answerer address to the bundled "m=" section represented by the answerer
BUNDLE-tag. In every other bundled "m=" section the answerer BUNDLE-tag. In every other bundled "m=" section the answerer
includes an SDP 'bundle-only' attribute and assigns a zero port value includes an SDP 'bundle-only' attribute and assigns a zero port value
to the "m=" section. to the "m=" section.
If the answerer does not want to keep a bundle-only "m=" section If the answerer does not want to keep a bundle-only "m=" section
within the BUNDLE group, it MUST reject the "m=" section within the BUNDLE group, it MUST reject the "m=" section
[Section 8.3.4]. [Section 8.3.4].
NOTE: If a bundled "m=" section in an offer contains a zero port NOTE: If a bundled "m=" section in an offer contains a zero port
value, but the "m=" section does not contain an SDP 'bundle-only' value, but the "m=" section does not contain an SDP 'bundle-only'
attribute, it is an indication that the offerer wants to disable the attribute, it is an indication that the offerer wants to disable the
"m=" section [Section 8.5.4]. "m=" section [Section 8.5.4].
8.3.1. Answerer Selection of Offerer Bundle Address 8.3.1. Answerer Selection of Offerer BUNDLE Address
In an offer, the bundled "m=" section represented by the offerer In an offer, the bundled "m=" section represented by the offerer
BUNDLE-tag contains the suggested offerer BUNDLE address, i.e, the BUNDLE-tag contains the suggested offerer BUNDLE address, i.e, the
address:port combination that the offerer wants to use for sending address:port combination that the offerer wants to use for sending
and receiving bundled media [Section 8.2.1]. The answerer MUST check and receiving bundled media [Section 8.2.1]. The answerer MUST check
whether that "m=" section fulfils the following criteria: whether that "m=" section fulfils the following criteria:
o The answerer will not move the "m=" section out of the BUNDLE o The answerer will not move the "m=" section out of the BUNDLE
group [Section 8.3.3]; and group [Section 8.3.3]; and
skipping to change at page 14, line 43 skipping to change at page 15, line 29
to the "m=" section that contains the selected offerer BUNDLE address to the "m=" section that contains the selected offerer BUNDLE address
in the corresponding offer. The answerer BUNDLE-tag represents that in the corresponding offer. The answerer BUNDLE-tag represents that
"m=" section in the answer. To every other bundled "m=" section the "m=" section in the answer. To every other bundled "m=" section the
answerer MUST assign a zero port value and include an SDP 'bundle- answerer MUST assign a zero port value and include an SDP 'bundle-
only' attribute. only' attribute.
The answerer MUST NOT assign an answerer BUNDLE address to an "m=" The answerer MUST NOT assign an answerer BUNDLE address to an "m="
section that is not within the BUNDLE group, or to an "m=" section section that is not within the BUNDLE group, or to an "m=" section
that is within another BUNDLE group. that is within another BUNDLE group.
[Section 18.1] shows an example of an answerer BUNDLE address [Section 8.3.5] and [Section 18.1] show an example of an answerer
selection. BUNDLE address selection.
8.3.3. 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 a bundled "m=" section out of a BUNDLE When an answerer wants to move a bundled "m=" section out of a BUNDLE
group in an answer, it MUST first check the following criteria: group in an answer, it MUST first check the following criteria:
o In the corresponding offer, an offerer BUNDLE address (previously o In the corresponding offer, an offerer BUNDLE address (previously
selected [Section 8.3.1] or new suggested [Section 8.5.1]) has selected [Section 8.3.1] or new suggested [Section 8.5.1]) has
been assigned to the "m=" section by the offerer; or been assigned to the "m=" section by the offerer; or
o In the corresponding offer, the "m=" section contains an SDP o In the corresponding offer, the "m=" section contains an SDP
'bundle-only' attribute and a zero port value. 'bundle-only' attribute and a zero port value.
If either criteria above is fulfilled, the answerer can not not move If either criteria above is fulfilled, the answerer can not move the
the "m=" section out of the BUNDLE group in the answer. The answerer "m=" section out of the BUNDLE group in the answer. The answerer can
can either reject the whole offer, or keep the "m=" section within either reject the whole offer, reject each bundled "m=" section
the BUNDLE group in the answer and later create an offer where the within the BUNDLE group [Section 8.3.4], or keep the "m=" section
"m=" section is moved out of the BUNDLE group [Section 8.5.3] within the BUNDLE group in the answer and later create an offer where
the "m=" section is moved out of the BUNDLE group [Section 8.5.3].
When the answerer generates an answer, in which it removes a bundled When the answerer generates an answer, in which it moves a bundled
"m=" section out of a BUNDLE group, the answerer: "m=" section out of a BUNDLE group, the answerer:
o MUST assign a unique address to the "m=" section; and o MUST assign a unique address to the "m=" section; and
o MUST NOT place the identification-tag associated with the "m=" o MUST NOT place the identification-tag associated with the "m="
section in the SDP 'group:BUNDLE' attribute identification-tag section in the SDP 'group:BUNDLE' attribute identification-tag
list associated with the BUNDLE group; and list associated with the BUNDLE group; and
o MUST NOT assign an SDP 'bundle-only' attribute to the "m=" o MUST NOT assign an SDP 'bundle-only' attribute to the "m="
section. section.
An answerer MUST NOT move an "m=" section from one BUNDLE group to An answerer MUST NOT move an "m=" section from one BUNDLE group to
another within an answer. If the answerer wants to move an "m=" another within an answer. If the answerer wants to move an "m="
section from one BUNDLE group to another it MUST first move the section from one BUNDLE group to another it MUST first move the "m="
BUNDLE group out of the current BUNDLE group, and then generate an section out of the current BUNDLE group, and then generate an offer
offer where the "m=" section is added to another BUNDLE group where the "m=" section is added to another BUNDLE group
[Section 8.5.2]. [Section 8.5.2].
8.3.4. Rejecting A Media Description In A BUNDLE Group 8.3.4. Rejecting a Media Description in a BUNDLE Group
When an answerer wants to reject a bundled "m=" section in an answer, When an answerer wants to reject a bundled "m=" section in an answer,
it MUST first check the following criteria: it MUST first check the following criteria:
o In the corresponding offer, an offerer BUNDLE address (previously o In the corresponding offer, an offerer BUNDLE address (previously
selected [Section 8.3.1] or new suggested [Section 8.5.1]) has selected [Section 8.3.1] or new suggested [Section 8.5.1]) has
been assigned to the "m=" section by the offerer. been assigned to the "m=" section by the offerer.
If either criteria above is fulfilled, the answerer can not not If the criteria above is fulfilled, the answerer can not reject the
reject the "m=" section in the answer. The answerer can either "m=" section in the answer (unless the answerer rejects each bundled
reject the whole offer, or keep the "m=" section within the BUNDLE "m=" section within the BUNDLE group). The answerer can either
group in the answer and later create an offer where the "m=" section reject the whole offer, reject each bundled "m=" section within the
is disabled of the BUNDLE group [Section 8.5.4] BUNDLE group, or keep the "m=" section within the BUNDLE group in the
answer and later create an offer where the "m=" section is disabled
within the BUNDLE group [Section 8.5.4].
When an answerer generates an answer, in which it rejects a bundled When an answerer generates an answer, in which it rejects a bundled
"m=" section, the answerer: "m=" section, the answerer:
o MUST assign a zero port value to the "m=" section, according to o MUST assign a zero port value to the "m=" section, according to
the procedures in [RFC3264]; and the procedures in [RFC3264]; and
o MUST NOT place the identification-tag associated with the "m=" o MUST NOT place the identification-tag associated with the "m="
section in the SDP 'group:BUNDLE' attribute identification-tag section in the SDP 'group:BUNDLE' attribute identification-tag
list associated with the BUNDLE group; and list associated with the BUNDLE group; and
o MUST NOT assign an SDP 'bundle-only' attribute to the "m=" o MUST NOT assign an SDP 'bundle-only' attribute to the "m="
section. section.
8.3.5. Example: SDP Answer 8.3.5. Example: SDP Answer
The example shows an SDP answer, based on the SDP offer in The example below shows an SDP answer, based on the SDP offer in
[Section 8.2.2]. The answers accepts both "m=" sections within the [Section 8.2.2]. The answerer accepts both "m=" sections within the
BUNDLE group. The answerer assigns the answerer BUNDLE address to BUNDLE group. The answerer assigns the answerer BUNDLE address to
the "m=" section represented by the answerer BUNDLE-tag. The the "m=" section represented by the answerer BUNDLE-tag. The
answerer assigns a zero port value and an SDP 'bundle-only' attribute answerer assigns a zero port value and an SDP 'bundle-only' attribute
to the other bundled "m=" section. to the other bundled "m=" section.
SDP Answer SDP Answer
v=0 v=0
o=bob 2808844564 2808844564 IN IP4 biloxi.example.com o=bob 2808844564 2808844564 IN IP4 biloxi.example.com
s= s=
skipping to change at page 17, line 47 skipping to change at page 18, line 33
o The offerer wants to disable the bundled "m=" section o The offerer wants to disable the bundled "m=" section
[Section 8.5.4]. [Section 8.5.4].
To every other "m=" section within the BUNDLE group, the offerer MUST To every other "m=" section within the BUNDLE group, the offerer MUST
assign a zero port value and an SDP 'bundle-only' attribute. assign a zero port value and an SDP 'bundle-only' attribute.
When the offerer generates a subsequent offer, the offerer BUNDLE-tag When the offerer generates a subsequent offer, the offerer BUNDLE-tag
MUST represent the bundled "m=" section to which the offerer BUNDLE MUST represent the bundled "m=" section to which the offerer BUNDLE
address (previously negotiated or new suggested) has been assigned. address (previously negotiated or new suggested) has been assigned.
8.5.1. 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 8.2.1], the offerer MUST: offerer BUNDLE address [Section 8.2.1], the offerer MUST:
o Assign the new suggested offerer BUNDLE address to exactly one o Assign the new suggested offerer BUNDLE address to exactly one
"m=" section within the BUNDLE group; and "m=" section within the BUNDLE group; and
o Assign a zero port value and an SDP 'bundle-only' attribute to o Assign a zero port value and an SDP 'bundle-only' attribute to
every other "m=" section within the BUNDLE group. every other "m=" section within the BUNDLE group.
8.5.2. 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=" section, the offerer MUST: bundled "m=" section, the offerer MUST:
o Assign the offerer BUNDLE address (previously selected o Assign the offerer BUNDLE address (previously selected
[Section 8.3.1] or new suggested [Section 8.5.1]) to the added [Section 8.3.1] or new suggested [Section 8.5.1]) to the added
"m=" section; or "m=" section; or
o Assign a zero port value and an SDP 'bundle-only' attribute to the o Assign a zero port value and an SDP 'bundle-only' attribute to the
added "m=" section (in this case the offerer BUNDLE address is added "m=" section (in this case the offerer BUNDLE address is
skipping to change at page 18, line 37 skipping to change at page 19, line 22
[Section 8.2.1]. [Section 8.2.1].
NOTE: If the offerer also wants to suggest a new offerer BUNDLE NOTE: If the offerer also wants to suggest a new offerer BUNDLE
address to the BUNDLE group, the offerer can assign the new suggested address to the BUNDLE group, the offerer can assign the new suggested
offerer BUNDLE address either to the added "m=" section, or to some offerer BUNDLE address either to the added "m=" section, or to some
other "m=" section within the BUNDLE group [Section 8.5.1]. other "m=" section within the BUNDLE group [Section 8.5.1].
[Section 18.3] shows an example where an offerer sends an offer in [Section 18.3] shows an example where an offerer sends an offer in
order to add a bundled "m=" section to a BUNDLE group. order to add a bundled "m=" section to a BUNDLE group.
8.5.3. 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=" section out of a BUNDLE group, the offerer: bundled "m=" section out of a BUNDLE group, the offerer:
o MUST assign a unique address to the "m=" section; and o MUST assign a unique address to the "m=" section; and
o MUST NOT place the identification-tag associated with the "m=" o MUST NOT place the identification-tag associated with the "m="
section in the SDP 'group:BUNDLE' attribute identification-tag section in the SDP 'group:BUNDLE' attribute identification-tag
list associated with the BUNDLE group; and list associated with the BUNDLE group; and
skipping to change at page 19, line 12 skipping to change at page 19, line 46
An offerer MUST NOT move an "m=" section from one BUNDLE group to An offerer MUST NOT move an "m=" section from one BUNDLE group to
another within a single offer. If the offerer wants to move an "m=" another within a single offer. If the offerer wants to move an "m="
section from one BUNDLE group to another it MUST first move the section from one BUNDLE group to another it MUST first move the
BUNDLE group out of the current BUNDLE group, and then generate a BUNDLE group out of the current BUNDLE group, and then generate a
second offer where the "m=" section is added to another BUNDLE group second offer where the "m=" section is added to another BUNDLE group
[Section 8.5.2]. [Section 8.5.2].
[Section 18.4] shows an example of an offer for moving an "m=" [Section 18.4] shows an example of an offer for moving an "m="
section out of a BUNDLE group. section out of a BUNDLE group.
8.5.4. 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=" section, the offerer: bundled "m=" section, the offerer:
o MUST assign a zero port value to the "m=" section, following the o MUST assign a zero port value to the "m=" section, following the
procedures in [RFC4566]; and 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="
section in the SDP 'group:BUNDLE' attribute identification-tag section in the SDP 'group:BUNDLE' attribute identification-tag
list associated with the BUNDLE group; and list associated with the BUNDLE group; and
o MUST NOT assign an SDP 'bundle-only' attribute to the "m=" o MUST NOT assign an SDP 'bundle-only' attribute to the "m="
section. section.
[Section 18.5] shows an example of an offer for disabling an "m=" [Section 18.5] shows an example of an offer and answer for disabling
section within a BUNDLE group. an "m=" section within a BUNDLE group.
9. Protocol Identification 9. Protocol Identification
Each "m=" section within a BUNDLE group MUST use the same transport- Each "m=" section within a BUNDLE group MUST use the same transport-
layer protocol. If bundled "m=" sections use different protocols on layer protocol. If bundled "m=" sections use different protocols on
top of the transport-layer protocol, there MUST exist a publicly top of the transport-layer protocol, there MUST exist a publicly
available specification which describes a mechanism, for this available specification which describes a mechanism how to associate
particular protocol combination, how to associate received data with received data with the correct protocol for this particular protocol
the correct protocol. combination.
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=" section, there MUST exist a publicly available bundled "m=" section, 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=" section. received data with the correct "m=" section.
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 it
not describe how to identify different protocols transported on DTLS. does not describe how to identify different protocols transported on
While the mechanism is generally applicable to other protocols and DTLS. While the mechanism is generally applicable to other protocols
transport-layer protocols, any such use requires further and 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 protocol, and how to associate received data with the transport-layer protocol, and how to associate received data with the
correct protocols. correct protocols.
9.1. 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, DTLS and SRTP protocols
Layer Security (DTLS) and SRTP protocols (in any combination). If an (in any combination). If an offer or answer includes a bundled "m="
offer or answer includes bundled "m=" section that represent these section that represents these protocols, the offerer or answerer MUST
protocols, the offerer or answerer MUST support the mechanism support the mechanism described in [RFC5764], and no explicit
described in [RFC5764], and no explicit negotiation is required in negotiation is required in order to indicate support and usage of the
order to indicate support and usage of the mechanism. mechanism.
[RFC5764] does not describe how to identify different protocols [RFC5764] does not describe how to identify different protocols
transported on DTLS, only how to identify the DTLS protocol itself. transported on DTLS, only how to identify the DTLS protocol itself.
If multiple protocols are transported on DTLS, there MUST exist a If multiple protocols are transported on DTLS, there MUST exist a
specification describing a mechanism for identifying each individual specification describing a mechanism for identifying each individual
protocol. In addition, if a received DTLS packet can be associated protocol. In addition, if a received DTLS packet can be associated
with more than one "m=" section, there MUST exist a specification with more than one "m=" section, there MUST exist a specification
which describes a mechanism for associating the received DTLS packet which describes a mechanism for associating the received DTLS packets
with the correct "m=" section. with the correct "m=" section.
[Section 10.2] describes how to associate the packets in a received [Section 10.2] describes how to associate the packets in a received
SRTP stream with the correct "m=" section. SRTP stream with the correct "m=" section.
10. RTP Considerations 10. RTP Considerations
10.1. Single RTP Session 10.1. Single RTP Session
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
skipping to change at page 20, line 51 skipping to change at page 21, line 34
sections representing RTP-based media within a BUNDLE group will sections representing RTP-based media within a BUNDLE group will
share a single SSRC numbering space [RFC3550]. share a 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="
sections only if each codec associated with the payload type sections only if each codec associated with the payload type
number shares an identical codec configuration [Section 10.1.1]. number shares an identical codec configuration [Section 10.1.1].
o The proto value in each bundled RTP-based "m=" section MUST be o The proto value in each bundled RTP-based "m=" section MUST be
identical (e.g. RTP/AVPF). identical (e.g., RTP/AVPF).
o The RTP MID header extension MUST be enabled, by including an SDP o The RTP MID header extension MUST be enabled, by including an SDP
'extmap' attribute [RFC8285], with a 'urn:ietf:params:rtp- 'extmap' attribute [RFC8285], with a 'urn:ietf:params:rtp-
hdrext:sdes:mid' URI value, in each bundled RTP-based "m=" section hdrext:sdes:mid' URI value, in each bundled RTP-based "m=" section
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
that originate from different bundled "m=" sections. that originate from different bundled "m=" sections.
NOTE: The last bullet above is to avoid sending multiple media types NOTE: The last bullet above is to avoid sending multiple media types
skipping to change at page 21, line 26 skipping to change at page 22, line 9
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=" section) source (possibly associated with a different bundled "m=" section)
after a delay of 5 RTCP reporting intervals (the delay is to ensure after 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 the SSRC has timed out, in case the RTCP BYE packet was lost
[RFC3550]). [RFC3550]).
10.1.1. Payload Type (PT) Value Reuse 10.1.1. Payload Type (PT) Value Reuse
Multiple bundled "m=" section might describe RTP based media. As all Multiple bundled "m=" sections might describe RTP based media. As
RTP based media associated with a BUNDLE group belong to the same RTP all RTP based media associated with a BUNDLE group belong to the same
session, in order for a given payload type value to be used inside RTP session, in order for a given payload type value to be used
more than one bundled "m=" section, all codecs associated with the inside more than one bundled "m=" section, all codecs associated with
payload type number MUST share an identical codec configuration. the 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
attribute values must be identical for all codecs that use the same attribute values must be identical for all codecs that use the same
payload type value. payload type value.
10.2. Associating RTP/RTCP Streams With Correct SDP Media Description 10.2. Associating RTP/RTCP Streams with Correct SDP Media Description
NOTE: The text in this section is copied from Appendix B of JSEP.
The community has not yet agreed on the text.
As described in [RFC3550], RTP packets are associated with RTP As described in [RFC3550], RTP packets are associated with RTP
streams [RFC7656]. Each RTP stream is identified by an SSRC value, streams [RFC7656]. Each RTP stream is identified by an SSRC value,
and each RTP packet includes an SSRC field that is used to associate and each RTP packet includes an SSRC field that is used to associate
the packet with the correct RTP stream. RTCP packets also use SSRCs the packet with the correct RTP stream. RTCP packets also use SSRCs
to identify which RTP streams the packet relates to. However, a RTCP to identify which RTP streams the packet relates to. However, a RTCP
packet can contain multiple SSRC fields, in the course of providing packet can contain multiple SSRC fields, in the course of providing
feedback or reports on different RTP streams, and therefore can be feedback or reports on different RTP streams, and therefore can be
associated with multiple such streams. associated with multiple such streams.
skipping to change at page 22, line 44 skipping to change at page 23, line 24
When using this mechanism, the mapping from an SSRC to an When using this mechanism, the mapping from an SSRC to an
identification-tag is carried in RTP header extensions or RTCP SDES identification-tag is carried in RTP header extensions or RTCP SDES
packets, as specified in Section 15. Since a compound RTCP packet packets, as specified in Section 15. Since a compound RTCP packet
can contain multiple RTCP SDES packets, and each RTCP SDES packet can can contain multiple RTCP SDES packets, and each RTCP SDES packet can
contain multiple chunks, a single RTCP packet can contain several contain multiple chunks, a single RTCP packet can contain several
SSRC to identification-tag mappings. The offerer and answerer SSRC to identification-tag mappings. The offerer and answerer
maintain tables used for routing that are updated each time an RTP/ maintain tables used for routing that are updated each time an RTP/
RTCP packet contains new information that affects how packets should RTCP packet contains new information that affects how packets should
be routed. be routed.
However, some implementations of may not include this identification- However, some implementations may not include this identification-tag
tag in their RTP and RTCP traffic when using the BUNDLE mechanism, in their RTP and RTCP traffic when using the BUNDLE mechanism, and
and instead use a payload type based mechanism to associate RTP instead use a payload type based mechanism to associate RTP streams
streams with SDP "m=" sections. In this situation, each "m=" section with SDP "m=" sections. In this situation, each "m=" section MUST
MUST use unique payload type values, in order for the payload type to use unique payload type values, in order for the payload type to be a
be a reliable indicator of the relevant "m=" section for the RTP reliable indicator of the relevant "m=" section for the RTP stream.
stream. Note that when using the payload type to associate RTP Note that when using the payload type to associate RTP streams with
streams with "m=" sections an RTP stream, identified by SSRC, will be "m=" sections an RTP stream, identified by its SSRC, will be mapped
mapped to an "m=" section when the first packet of that RTP stream is to an "m=" section when the first packet of that RTP stream is
received, and the mapping will not be changed even if the payload received, and the mapping will not be changed even if the payload
type used by that RTP stream changes. In other words, the SSRC type used by that RTP stream changes. In other words, the SSRC
cannot to "move" to a different "m=" section simply by changing the cannot "move" to a different "m=" section simply by changing the
payload type. payload type.
Applications can implement RTP stacks in many different ways. The Applications can implement RTP stacks in many different ways. The
algorithm below details one way that RTP streams can be associated algorithm below details one way that RTP streams can be associated
with "m=" sections, but is not meant to be prescriptive about exactly with "m=" sections, but is not meant to be prescriptive about exactly
how an RTP stack needs to be implemented. Applications MAY use any how an RTP stack needs to be implemented. Applications MAY use any
algorithm that achieves equivalent results to those described in the algorithm that achieves equivalent results to those described in the
algorithm below. algorithm below.
To prepare to associate RTP streams with the correct "m=" section, To prepare to associate RTP streams with the correct "m=" section,
the following steps MUST be followed for each BUNDLE group. the following steps MUST be followed for each BUNDLE group:
Construct a table mapping MID to "m=" section for each "m=" Construct a table mapping MID to "m=" section for each "m="
section in this BUNDLE group. Note that an "m=" section may only section in this BUNDLE group. Note that an "m=" section may only
have one MID. have one MID.
Construct a table mapping SSRCs of incoming RTP streams to "m=" Construct a table mapping SSRCs of incoming RTP streams to "m="
section for each "m=" section in this BUNDLE group and for each section for each "m=" section in this BUNDLE group and for each
SSRC configured for receiving in that "m=" section. SSRC configured for receiving in that "m=" section.
Construct a table mapping the SSRC of each outgoing RTP stream to Construct a table mapping the SSRC of each outgoing RTP stream to
"m=" section for each "m=" section in this BUNDLE group and for "m=" section for each "m=" section in this BUNDLE group and for
each SSRC configured for sending in that "m=" section. each SSRC configured for sending in that "m=" section.
Construct a table mapping payload type to "m=" section for each Construct a table mapping payload type to "m=" section for each
"m=" section in the BUNDLE group and for each payload type "m=" section in the BUNDLE group and for each payload type
configured for receiving in that "m=" section. If any payload configured for receiving in that "m=" section. If any payload
type is configured for receiving in more than one "m=" section in type is configured for receiving in more than one "m=" section in
the BUNDLE group, do not it include it in the table, as it cannot the BUNDLE group, do not include it in the table, as it cannot be
be used to uniquely identify a "m=" section. used to uniquely identify an "m=" section.
Note that for each of these tables, there can only be one mapping Note that for each of these tables, there can only be one mapping
for any given key (MID, SSRC, or PT). In other words, the tables for any given key (MID, SSRC, or PT). In other words, the tables
are not multimaps. are not multimaps.
As "m=" sections are added or removed from the BUNDLE groups, or As "m=" sections are added or removed from the BUNDLE groups, or
their configurations are changed, the tables above MUST also be their configurations are changed, the tables above MUST also be
updated. updated.
When an RTP packet is received, it MUST be delivered to the RTP When an RTP packet is received, it MUST be delivered to the RTP
stream corresponding to its SSRC. That RTP stream MUST then be stream corresponding to its SSRC. That RTP stream MUST then be
associated with the correct "m=" section within a BUNDLE group, for associated with the correct "m=" section within a BUNDLE group, for
additional processing, according to the following steps. additional processing, according to the following steps:
If the MID associated with the RTP stream is not in the table If the MID associated with the RTP stream is not in the table
mapping MID to "m=" section, then the RTP stream is not decoded mapping MID to "m=" section, then the RTP stream is not decoded
and the payload data is discarded. and the payload data is discarded.
If the packet has a MID, and the packet's extended sequence number If the packet has a MID, and the packet's extended sequence number
is greater than that of the last MID update, as discussed in is greater than that of the last MID update, as discussed in
[RFC7941], Section 4.2.6, update the MID associated with the RTP [RFC7941], Section 4.2.6, update the MID associated with the RTP
stream to match the MID carried in the RTP packet, then update the stream to match the MID carried in the RTP packet, then update the
mapping tables to include an entry that maps the SSRC of that RTP mapping tables to include an entry that maps the SSRC of that RTP
skipping to change at page 24, line 31 skipping to change at page 25, line 10
If the payload type used by the RTP stream is in the payload type If the payload type used by the RTP stream is in the payload type
table, update the incoming SSRC mapping table to include an entry table, update the incoming SSRC mapping table to include an entry
that maps the RTP stream's SSRC to the "m=" section for that that maps the RTP stream's SSRC to the "m=" section for that
payload type. Associate the RTP stream with the corresponding payload type. Associate the RTP stream with the corresponding
"m=" section. "m=" section.
Otherwise, mark the RTP stream as not for decoding and discard the Otherwise, mark the RTP stream as not for decoding and discard the
payload. payload.
If the RTP packet contains one of more contributing source (CSRC) If the RTP packet contains one or more contributing source (CSRC)
identifiers, then each CSRC is looked up in the incoming SSRC table identifiers, then each CSRC is looked up in the incoming SSRC table
and a copy of the RTP packet is associated with the corresponding and a copy of the RTP packet is associated with the corresponding
"m=" section for additional processing. "m=" section for additional processing.
For each RTCP packet received (including each RTCP packet that is For each RTCP packet received (including each RTCP packet that is
part of a compound RTCP packet), the packet is processed as usual by part of a compound RTCP packet), the packet is processed as usual by
the RTP layer, then is passed to the "m=" sections corresponding to the RTP layer, then passed to the "m=" sections corresponding to the
the RTP streams it contains information about for additional RTP streams it contains information about for additional processing.
processing. This routing is type-dependent, as each kind of RTCP This routing is type-dependent, as each kind of RTCP packet has its
packet has its own mechanism for associating it with the relevant RTP own mechanism for associating it with the relevant RTP streams.
streams.
RTCP packets for which no appropriate "m=" section can be identified RTCP packets for which no appropriate "m=" section can be identified
MUST be processed as usual by the RTP layer, updating the metadata MUST be processed as usual by the RTP layer, updating the metadata
associated with the corresponding RTP streams, but are not passed to associated with the corresponding RTP streams, but are not passed to
any "m=" section. This situation can occur with certain multiparty any "m=" section. This situation can occur with certain multiparty
RTP topologies, or when RTCP packets are sent containing a subset of RTP topologies, or when RTCP packets are sent containing a subset of
the SDES information. the SDES information.
Rules for additional processing of the various types of RTCP packets Rules for additional processing of the various types of RTCP packets
are explained below. are explained below.
If the RTCP packet is of type SDES, for each chunk in the packet If the RTCP packet is of type SDES, for each chunk in the packet
whose SSRC is found in the incoming SSRC table, deliver a copy of whose SSRC is found in the incoming SSRC table, deliver a copy of
the SDES packet to the "m=" section associated with that SSRC. In the SDES packet to the "m=" section associated with that SSRC. In
addition, for any SDES MID items contained in these chunks, if the addition, for any SDES MID items contained in these chunks, if the
MID is found in the table mapping MID to "m=" section, update the MID is found in the table mapping MID to "m=" section, update the
incoming SSRC table to include an entry that maps the RTP stream incoming SSRC table to include an entry that maps the RTP stream
associated with chunk's SSRC to the "m=" section associated with associated with the chunk's SSRC to the "m=" section associated
that MID, unless the packet is older than the packet that most with that MID, unless the packet is older than the packet that
recently updated the mapping for this SSRC, as discussed in most recently updated the mapping for this SSRC, as discussed in
[RFC7941], Section 4.2.6. [RFC7941], Section 4.2.6.
Note that if an SDES packet is received as part of a compound RTCP Note that if an SDES packet is received as part of a compound RTCP
packet, the SSRC to "m=" section mapping may not exist until the packet, the SSRC to "m=" section mapping may not exist until the
SDES packet is handled (e.g., in the case where RTCP for a source SDES packet is handled (e.g., in the case where RTCP for a source
is received before any RTP packets). Therefore, when processing a is received before any RTP packets). Therefore, when processing a
compound packet, any contained SDES packet MUST be handled first. compound packet, any contained SDES packet MUST be handled first.
Note that this is a backwards change from [RFC3550] Section 6.1, Note that this is a change from [RFC3550] Section 6.1, which
which states that "Each individual RTCP packet in the compound states that "Each individual RTCP packet in the compound packet
packet may be processed independently with no requirements upon may be processed independently with no requirements upon the order
the order or combination of packets". or combination of packets".
If the RTCP packet is of type BYE, it indicates that the RTP If the RTCP packet is of type BYE, it indicates that the RTP
streams referenced in the packet are ending. Therefore, for each streams referenced in the packet are ending. Therefore, for each
SSRC indicated in the packet that is found in the incoming SSRC SSRC indicated in the packet that is found in the incoming SSRC
table, first deliver a copy of the BYE packet to the "m=" section table, first deliver a copy of the BYE packet to the "m=" section
associated with that SSRC, but then remove the entry for that SSRC associated with that SSRC, then remove the entry for that SSRC
from the incoming SSRC table after an appropriate delay to account from the incoming SSRC table after an appropriate delay to account
for "straggler packets", as specified in [RFC3550], Section 6.2.1. for "straggler packets", as specified in [RFC3550], Section 6.2.1.
If the RTCP packet is of type SR or RR, for each report block in If the RTCP packet is of type SR or RR, for each report block in
the report whose "SSRC of source" is found in the outgoing SSRC the report whose "SSRC of source" is found in the outgoing SSRC
table, deliver a copy of the SR or RR packet to the "m=" section table, deliver a copy of the SR or RR packet to the "m=" section
associated with that SSRC. In addition, if the packet is of type associated with that SSRC. In addition, if the packet is of type
SR, and the sender SSRC for the packet is found in the incoming SR, and the sender SSRC for the packet is found in the incoming
SSRC table, deliver a copy of the SR packet to the "m=" section SSRC table, deliver a copy of the SR packet to the "m=" section
associated with that SSRC. associated with that SSRC.
If the implementation supports RTCP XR and the packet is of type If the implementation supports RTCP XR and the packet is of type
XR, as defined in [RFC3611], for each report block in the report XR, as defined in [RFC3611], for each report block in the report
whose "SSRC of source" is is found in the outgoing SSRC table, whose "SSRC of source" is found in the outgoing SSRC table,
deliver a copy of the XR packet to the "m=" section associated deliver a copy of the XR packet to the "m=" section associated
with that SSRC. In addition, if the sender SSRC for the packet is with that SSRC. In addition, if the sender SSRC for the packet is
found in the incoming SSRC table, deliver a copy of the XR packet found in the incoming SSRC table, deliver a copy of the XR packet
to the "m=" section associated with that SSRC. to the "m=" section associated with that SSRC.
If the RTCP packet is a feedback message of type RTPFB or PSFB, as If the RTCP packet is a feedback message of type RTPFB or PSFB, as
defined in [RFC4585], it will contain a media source SSRC, and defined in [RFC4585], it will contain a media source SSRC, and
this SSRC is used for routing certain subtypes of feedback this SSRC is used for routing certain subtypes of feedback
messages. However, several subtypes of PSFB messages include messages. However, several subtypes of PSFB and RTPFB messages
target SSRC(s) in a section called Feedback Control Information include target SSRC(s) in a section called Feedback Control
(FCI). For these messages, the target SSRC(s) are used for Information (FCI). For these messages, the target SSRC(s) are
routing. used for routing.
If the RTCP packet is a feedback packet that does not include If the RTCP packet is a feedback packet that does not include
target SSRCs in its FCI section, and the media source SSRC is target SSRCs in its FCI section, and the media source SSRC is
found in the outgoing SSRC table, deliver the feedback packet to found in the outgoing SSRC table, deliver the feedback packet to
the "m=" section associated with that SSRC. RTPFB and PSFB types the "m=" section associated with that SSRC. RTPFB and PSFB types
that are handled in this way include: that are handled in this way include:
Generic NACK: [RFC4585] (PT=RTPFB, FMT=1). Generic NACK: [RFC4585] (PT=RTPFB, FMT=1).
Picture Loss Indication (PLI): [RFC4585] (PT=PSFB, FMT=1). Picture Loss Indication (PLI): [RFC4585] (PT=PSFB, FMT=1).
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If the RTCP packet is a feedback message that does include target If the RTCP packet is a feedback message that does include target
SSRC(s) in its FCI section, it can either be a request or a SSRC(s) in its FCI section, it can either be a request or a
notification. Requests reference a RTP stream that is being sent notification. Requests reference a RTP stream that is being sent
by the message recipient, whereas notifications are responses to by the message recipient, whereas notifications are responses to
an earlier request, and therefore reference a RTP stream that is an earlier request, and therefore reference a RTP stream that is
being received by the message recipient. being received by the message recipient.
If the RTCP packet is a feedback request that includes target If the RTCP packet is a feedback request that includes target
SSRC(s), for each target SSRC that is found in the outgoing SSRC SSRC(s), for each target SSRC that is found in the outgoing SSRC
table, deliver a copy of the RTCP packet to the "m=" section table, deliver a copy of the RTCP packet to the "m=" section
associated with that SSRC. PSFB types that are handled in this associated with that SSRC. PSFB and RTPFB types that are handled
way include: in this way include:
Full Intra Request (FIR): [RFC5104] (PT=PSFB, FMT=4). Full Intra Request (FIR): [RFC5104] (PT=PSFB, FMT=4).
Temporal-Spatial Trade-off Request (TSTR): [RFC5104] (PT=PSFB, Temporal-Spatial Trade-off Request (TSTR): [RFC5104] (PT=PSFB,
FMT=5). FMT=5).
H.271 Video Back Channel Message (VBCM): [RFC5104] (PT=PSFB, H.271 Video Back Channel Message (VBCM): [RFC5104] (PT=PSFB,
FMT=7). FMT=7).
Temporary Maximum Media Bit Rate Request (TMMBR): [RFC5104]
(PT=RTPFB, FMT=3).
Layer Refresh Request (LRR): [I-D.ietf-avtext-lrr] (PT=PSFB, Layer Refresh Request (LRR): [I-D.ietf-avtext-lrr] (PT=PSFB,
FMT=TBD). FMT=TBD).
If the RTCP packet is a feedback notification that include target If the RTCP packet is a feedback notification that includes target
SSRC(s), for each target SSRC that is found in the incoming SSRC SSRC(s), for each target SSRC that is found in the incoming SSRC
table, deliver a copy of the RTCP packet to the "m=" section table, deliver a copy of the RTCP packet to the "m=" section
associated with the RTP stream with matching SSRC. PSFB types associated with the RTP stream with matching SSRC. PSFB and RTPFB
that are handled in this way include: types that are handled in this way include:
Temporal-Spatial Trade-off Notification (TSTN): [RFC5104] Temporal-Spatial Trade-off Notification (TSTN): [RFC5104]
(PT=PSFB, FMT=6). This message is a notification in response (PT=PSFB, FMT=6). This message is a notification in response
to a prior TSTR. to a prior TSTR.
Temporary Maximum Media Bit Rate Notification (TMMBN): [RFC5104]
(PT=RTPFB, FMT=4). This message is a notification in response
to a prior TMMBR, but can also be sent unsolicited.
If the RTCP packet is of type APP, then it is handled in an If the RTCP packet is of type APP, then it is handled in an
application specific manner. If the application does not application specific manner. If the application does not
recognise the APP packet, then it MUST be discarded. recognise the APP packet, then it MUST be discarded.
10.3. RTP/RTCP Multiplexing 10.3. RTP/RTCP Multiplexing
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.
skipping to change at page 27, line 40 skipping to change at page 28, line 30
multiplexing for RTP-based media associated with a BUNDLE group. multiplexing for RTP-based media associated with a BUNDLE group.
The mux category [I-D.ietf-mmusic-sdp-mux-attributes] of the SDP The mux category [I-D.ietf-mmusic-sdp-mux-attributes] of the SDP
'rtcp-mux' and 'rtcp-mux-only' attributes is IDENTICAL. Section 8.1 'rtcp-mux' and 'rtcp-mux-only' attributes is IDENTICAL. Section 8.1
describes the details regarding which bundled "m=" sections an describes the details regarding which bundled "m=" sections an
offerer and answerer associates the attributes with. offerer and answerer associates the attributes with.
RTP/RTCP multiplexing only applies to RTP-based media. However, as RTP/RTCP multiplexing only applies to RTP-based media. However, as
described in Section 8.1, within a BUNDLE group the SDP 'rtcp-mux' described in Section 8.1, within a BUNDLE group the SDP 'rtcp-mux'
and SDP 'rtcp-mux-only' attributes might be included in a non-RTP- and SDP 'rtcp-mux-only' attributes might be included in a non-RTP-
based bundled "m=" section. based bundled "m=" section (if such "m=" line is represented by a
BUNDLE-tag).
10.3.1.1. Generating the Initial SDP Offer 10.3.1.1. Generating the Initial SDP Offer
When an offerer generates an initial offer, if the offer contains one When an offerer generates an initial offer, if the offer contains one
or more RTP-based bundled "m=" sections (or, if there is a chance or more RTP-based bundled "m=" sections (or, if there is a chance
that RTP-based "m=" sections will later be added to the BUNDLE that RTP-based "m=" sections will later be added to the BUNDLE
group), the offerer MUST include an SDP 'rtcp-mux' attribute group), the offerer MUST include an SDP 'rtcp-mux' attribute
[RFC5761] in one or more "m=" sections, following the procedures for [RFC5761] in each bundled "m=" section (excluding any bundle-only
IDENTICAL mux category attributes in Section 8.1. In addition, the "m=" sections), following the procedures for IDENTICAL mux category
offerer MAY include an SDP 'rtcp-mux-only' attribute attributes in Section 8.1. In addition, the offerer MAY include an
[I-D.ietf-mmusic-mux-exclusive] in the same "m=" section. SDP 'rtcp-mux-only' attribute [I-D.ietf-mmusic-mux-exclusive] in a
RTP-based bundled "m=" section.
NOTE: Whether the offerer associates the SDP 'rtcp-mux-only' NOTE: Whether the offerer associates the SDP 'rtcp-mux-only'
attribute depends on whether the offerer supports fallback to usage attribute depends on whether the offerer supports fallback to usage
of a separate port for RTCP in case the answerer moves one or more of a separate port for RTCP in case the answerer moves one or more
RTP-based "m=" section out of the BUNDLE group in the answer. RTP-based "m=" section out of the BUNDLE group in the answer.
NOTE: If the offerer includes an SDP 'rtcp-mux' attribute in one or NOTE: If the offerer includes an SDP 'rtcp-mux' attribute in the
more bundled "m=" sections, but does not include an SDP 'rtcp-mux- bundled "m=" sections, but does not include an SDP 'rtcp-mux-only'
only' attribute, the offerer can also include an SDP 'rtcp' attribute attribute, the offerer can also include an SDP 'rtcp' attribute
[RFC3605] in one or more RTP-based "m=" sections in order to provide
a fallback port for RTCP, as described in [RFC5761]. However, the [RFC3605] in one or more RTP-based bundled "m=" sections in order to
fallback port will only be used for RTP-based "m=" sections moved out provide a fallback port for RTCP, as described in [RFC5761].
of the BUNDLE group by the answerer. However, the fallback port will only be used for RTP-based "m="
sections moved out of the BUNDLE group by the answerer.
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=" section (excluding a bundle- unique in each bundled RTP-based "m=" section (excluding a bundle-
only "m=" section), similar to RTP. only "m=" section), similar to RTP.
10.3.1.2. Generating the SDP Answer 10.3.1.2. Generating the SDP Answer
When an answerer generates an answer, if the answerer supports RTP- When an answerer generates an answer, if the answerer supports RTP-
based media, and if a bundled "m=" section in the offer contained an based media, and if a bundled "m=" section in the offer contained an
SDP 'rtcp-mux' attribute, the answerer MUST enable usage of RTP/RTCP SDP 'rtcp-mux' attribute, the answerer MUST enable usage of RTP/RTCP
multiplexing, even if there currently are no RTP-based "m=" sections multiplexing, even if there currently are no RTP-based "m=" sections
within the BUNDLE group. The answerer MUST include an SDP 'rtcp-mux' within the BUNDLE group. The answerer MUST include an SDP 'rtcp-mux'
attribute in "m=" sections within the BUNDLE group in the answer attribute in the bundled "m=" section represented by the answerer
following the procedures for IDENTICAL mux category attributes in BUNDLE-tag, following the procedures for IDENTICAL mux category
Section 8.1. In addition, if the "m=" section in the offer contained attributes in Section 8.1. In addition, if the "m=" section in the
an an SDP "rtcp-mux-only" attribute, the answerer MUST include an SDP offer contained an SDP "rtcp-mux-only" attribute, the answerer MUST
"rtcp-mux-only" attribute to the "m=" section in the answer. include an SDP "rtcp-mux-only" attribute in the bundled "m=" section
represented by the answerer BUNDLE-tag in the answer.
If the "m=" section associated with the offerer BUNDLE-tag in the If the "m=" section represented by the offerer BUNDLE-tag in the
offer contained an SDP 'rtcp-mux-only' attribute, and if the answerer offer contained an SDP 'rtcp-mux-only' attribute, and if the answerer
moves an RTP-based "m=" section out of the BUNDLE group in the answer moves an RTP-based "m=" section out of the BUNDLE group in the answer
Section 8.3.3, the answerer MUST either include the attribute with in [Section 8.3.3], the answerer MUST either include the attribute in
moved "m=" section (and enable RTP/RTCP multiplexing for the media the moved "m=" section (and enable RTP/RTCP multiplexing for the
associated with the "m=" section), or reject the "m=" section media associated with the "m=" section), or reject the "m=" section
Section 8.3.4. [Section 8.3.4].
The answerer MUST NOT include an SDP 'rtcp' attribute in any "m=" The answerer MUST NOT include an SDP 'rtcp' attribute in any "m="
section within the BUNDLE group in the answer. The answerer will use section within the BUNDLE group in the answer. The answerer will use
the port value of the selected offerer BUNDLE address for sending RTP the port value of the selected offerer BUNDLE address for sending RTP
and RTCP packets associated with each RTP-based bundled "m=" section and RTCP packets associated with each RTP-based bundled "m=" section
towards the offerer. towards the 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 exchange, the answerer MUST
include an SDP 'rtcp-mux' attribute in the "m=" section associated include an SDP 'rtcp-mux' attribute in the "m=" section associated
with the answerer BUNDLE-tag in the answer. It is not possible to with the answerer BUNDLE-tag in the answer. It is not possible to
disable RTP/RTCP multiplexing within a BUNDLE group. disable RTP/RTCP multiplexing within a BUNDLE group.
10.3.1.3. 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 10.3.1.2), 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=" section towards the answerer. with each RTP-based bundled "m=" section 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=" accepted the usage of RTP/RTCP multiplexing for RTP-based "m="
sections that the answerer included in the BUNDLE group. sections that the answerer included in the BUNDLE group.
10.3.1.4. Modifying the Session 10.3.1.4. Modifying the Session
skipping to change at page 29, line 23 skipping to change at page 30, line 16
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=" section towards the answerer. with each RTP-based bundled "m=" section 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=" accepted the usage of RTP/RTCP multiplexing for RTP-based "m="
sections that the answerer included in the BUNDLE group. sections that the answerer included in the BUNDLE group.
10.3.1.4. Modifying the Session 10.3.1.4. Modifying the Session
When an offerer generates a subsequent offer, the offerer MUST When an offerer generates a subsequent offer, the offerer MUST
include an SDP 'rtcp-mux' attribute in a bundled "m=" section, include an SDP 'rtcp-mux' attribute in the bundled "m=" section
following the procedures for IDENTICAL mux category attributes in represented by the offerer BUNDLE-tag, following the procedures for
Section 8.1. IDENTICAL mux category attributes in Section 8.1.
If the offerer wants to add a bundled RTP-based "m=" section to the
BUNDLE group, it MAY also include an SDP 'rtcp-mux-only' attribute in
a bundled "m=" section, following the procedures for IDENTICAL mux
category attributes in Section 8.1. This allows the offerer to
mandate RTP/RTCP multiplexing for the added "m=" section (or the "m="
section to be rejected by the answerer) even if the answerer does not
accept the "m=" section within the BUNDLE group.
11. ICE Considerations 11. ICE Considerations
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 the BUNDLE transport has been established, ICE connectivity o When the BUNDLE transport has been established, ICE connectivity
checks and keep-alives only need to be performed for the BUNDLE checks and keep-alives only need to be performed for the BUNDLE
transport, instead of per individual "m=" section within the transport, instead of per individual "m=" section within the
BUNDLE group. BUNDLE group.
o In an offer, if the offer assigns a unique address to one or more o In an offer, if the offer assigns a unique address to one or more
bundled "m=" sections (excluding any bundle-only "m=" section), bundled "m=" sections (excluding any bundle-only "m=" sections),
the offerer MUST include ICE-related media-level attributes in the offerer MUST include ICE-related media-level attributes in
each of those "m=" sections. If the offerer assigns an offerer each of those "m=" sections. If the offerer assigns an offerer
BUNDLE address (previously selected [Section 8.3.1] or new BUNDLE address (previously selected [Section 8.3.1] or new
suggested [Section 8.5.1]) to a bundled "m=" section (the "m=" suggested [Section 8.5.1]) to a bundled "m=" section (the "m="
section represented by the offerer BUNDLE-tag), the offerer only section represented by the offerer BUNDLE-tag), the offerer only
includes ICE-related media-level SDP attributes in that "m=" includes ICE-related media-level SDP attributes in that "m="
section, following the procedures in Section 8.1. section, following the procedures in Section 8.1.
o In an answer, the answerer only includes ICE-related media-level o In an answer, the answerer only includes ICE-related media-level
SDP attributes in the bundled "m=" section to which the answerer SDP attributes in the bundled "m=" section to which the answerer
has assigned the answerer BUNDLE address (the "m=" section has assigned the answerer BUNDLE address (the "m=" section
represented by the answerer BUNDLE-tag), following the procedures represented by the answerer BUNDLE-tag), following the procedures
in Section 8.1. in Section 8.1.
Initially, before ICE has produced a candidate pair that will be used Initially, before ICE has produced a candidate pair that will be used
for media, there might by multiple transports established (if for media, there might be multiple transports established (if
multiple candidate pairs are tested). Once ICE has produced a multiple candidate pairs are tested). Once ICE has produced a
transport that will be used for media, that becomes the BUNDLE transport that will be used for media, that becomes the BUNDLE
transport. transport.
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, and the procedures in this section only apply when the
ICE mechanism is used.
11.1. SDP Offer/Answer Procedures 11.1. SDP Offer/Answer Procedures
When an offerer assigns a unique address to one or more bundled "m=" When an offerer assigns a unique address to one or more bundled "m="
sections (excluding any bundle-only "m=" section), the offerer MUST sections (excluding any bundle-only "m=" section), the offerer MUST
include SDP 'candidate' attributes (and other applicable ICE-related include SDP 'candidate' attributes (and other applicable ICE-related
media-level SDP attributes), containing unique ICE properties media-level SDP attributes), containing unique ICE properties
(candidates etc), in each of those "m=" sections, follwoing the (candidates etc), in each of those "m=" sections, following the
procedures in [I-D.ietf-mmusic-ice-sip-sdp]. procedures in [I-D.ietf-mmusic-ice-sip-sdp].
When an offerer assigns a BUNDLE address (previously selected or new When an offerer assigns a BUNDLE address (previously selected or new
suggested) to a bundled "m=" section, (the "m=" section represented suggested) to a bundled "m=" section, (the "m=" section represented
by the offerer BUNDLE-tag) the offerer MUST only include SDP by the offerer BUNDLE-tag) the offerer MUST only include SDP
'candidate' attributes (and other applicable ICE-related media-level 'candidate' attributes (and other applicable ICE-related media-level
SDP attributes) in that "m=" section, following the procedures in SDP attributes) in that "m=" section, following the procedures in
Section 8.1. Section 8.1.
When an answerer assigns a BUNDLE address to an "m=" section within a When an answerer assigns a BUNDLE address to an "m=" section within a
skipping to change at page 31, line 10 skipping to change at page 31, line 43
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 procedures in Section 8.1 when offerer and answerer follow the procedures in Section 8.1 when
deciding whether to include an attribute in a bundled "m=" section. deciding whether to include an attribute in a bundled "m=" section.
However, in the case of ICE-related media-level attributes, the rules However, in the case of ICE-related media-level attributes, the rules
apply to all attributes (see note below), even if they belong to a apply to all attributes (see note below), even if they belong to a
different mux category. different 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]: 'candidate', 'remote-
candidates', 'ice-mismatch', 'ice-ufrag', 'ice-pwd', and 'ice- candidates', 'ice-mismatch', 'ice-ufrag', 'ice-pwd', and 'ice-
pacing'. pacing'.
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) become 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
of DTLS-SRTP is not negotiated as part of the multimedia session usage of DTLS-SRTP is not negotiated as part of the multimedia
(e.g., SIP session [RFC3261]. session (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. RTP Header Extensions Consideration 13. RTP Header Extensions Consideration
When [RFC8285] RTP header extensions are used in the context of this When [RFC8285] RTP header extensions are used in the context of this
specification, the identifier used for a given extension MUST specification, the identifier used for a given extension MUST
skipping to change at page 33, line 39 skipping to change at page 34, line 30
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.
14.6. New text replacing section 8.2 (2nd paragraph) of RFC 3264 14.6. 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.
14.7. Original text of section 8.4 (6th paragraph) of RFC 3264 14.7. 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
skipping to change at page 34, line 36 skipping to change at page 35, line 27
tags with "m=" sections within SDP Offers and Answers, using the tags with "m=" sections 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=" section. an "m=" section.
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 SDES header extension [RFC7941], which section also defines a new RTP SDES header extension [RFC7941], which
is used to carry the 'MID' RTCP SDES item in RTP packets. is used to carry the 'MID' RTCP SDES item in RTP packets.
The SDES item and RTP SDES header extension make it possible for a The SDES item and RTP SDES header extension make it possible for a
receiver to associate each RTP stream with with a specific "m=" receiver to associate each RTP stream with a specific "m=" section,
section, with which the receiver has associated an identification- with which the receiver has associated an identification-tag, even if
tag, even if those "m=" sections are part of the same RTP session. those "m=" sections are part of the same RTP session. The RTP SDES
The RTP SDES header extension also ensures that the media recipient header extension also ensures that the media recipient gets the
gets the identification-tag upon receipt of the first decodable media identification-tag upon receipt of the first decodable media and is
and is able to associate the media with the correct application. able to associate the media with the correct application.
A media recipient informs the media sender about the identification- A media recipient informs the media sender about the identification-
tag associated with an "m=" section through the use of an 'mid' tag associated with an "m=" section through the use of an 'mid'
attribute [RFC5888]. The media sender then inserts the attribute [RFC5888]. The media sender then inserts the
identification-tag in RTCP and RTP packets sent to the media identification-tag in RTCP and RTP packets sent to the media
recipient. 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 signaling 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 after 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.
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The RTP SDES header extension for carrying the 'MID' RTCP SDES SHOULD The RTP SDES header extension for carrying the 'MID' RTCP SDES SHOULD
be included in some RTP packets at the start of the session and be included in some RTP packets at the start of the session and
whenever the SSRC changes. It might also be useful to include the whenever the SSRC changes. It might also be useful to include the
header extension in RTP packets that comprise access points in the header extension in RTP packets that comprise access points in the
media (e.g., with video I-frames). The exact number of RTP packets media (e.g., with video I-frames). The exact number of RTP packets
in which this header extension is sent is intentionally not specified in which this header extension is sent is intentionally not specified
here, as it will depend on expected packet loss rate and loss here, as it will depend on expected packet loss rate and loss
patterns, the overhead the application can tolerate, and the patterns, the overhead the application can tolerate, and the
importance of immediate receipt of the identification-tag. importance of immediate receipt of the identification-tag.
For robustness purpose, endpoints need to be prepared for situations For robustness, endpoints need to be prepared for situations where
where the reception of the identification-tag is delayed, and SHOULD the reception of the identification-tag is delayed, and SHOULD NOT
NOT terminate sessions in such cases, as the identification-tag is terminate sessions in such cases, as the identification-tag is likely
likely to arrive soon. to arrive soon.
15.1. RTCP MID SDES Item 15.1. 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.
skipping to change at page 38, line 24 skipping to change at page 39, line 15
Semantics Token Reference Semantics Token Reference
------------------------------------- ------ --------- ------------------------------------- ------ ---------
Media bundling BUNDLE [RFCXXXX] Media bundling BUNDLE [RFCXXXX]
17. Security Considerations 17. Security Considerations
The security considerations defined in [RFC3264] and [RFC5888] apply The security considerations defined in [RFC3264] and [RFC5888] apply
to the BUNDLE extension. Bundle does not change which information, to the BUNDLE extension. Bundle does not change which information,
e.g., RTP streams, flows over the network, with the exception of the e.g., RTP streams, flows over the network, with the exception of the
usage of the MID SDES item as discussed below. Primarily it changes usage of the MID SDES item as discussed below. Primarily it changes
which addresses and ports, and thus in which (RTP) sessions that the which addresses and ports, and thus in which (RTP) sessions the
information is flowing in. This affects the security contexts being information is flowing. This affects the security contexts being
used and can cause previously separated information flows to share used and can cause previously separated information flows to share
the same security context. This has very little impact on the the same security context. This has very little impact on the
performance of the security mechanism of the RTP sessions. In cases performance of the security mechanism of the RTP sessions. In cases
where one would have applied different security policies on the where one would have applied different security policies on the
different RTP streams being bundled, or where the parties having different RTP streams being bundled, or where the parties having
access to the security contexts would have differed between the RTP access to the security contexts would have differed between the RTP
stream, additional analysis of the implications are needed before streams, additional analysis of the implications are needed before
selecting to apply BUNDLE. selecting to apply BUNDLE.
The identification-tag, independent of transport, RTCP SDES packet or The identification-tag, independent of transport, RTCP SDES packet or
RTP header extension, can expose the value to parties beyond the RTP header extension, can expose the value to parties beyond the
signaling chain. Therefore, the identification-tag values MUST be signaling chain. Therefore, the identification-tag values MUST be
generated in a fashion that does not leak user information, e.g., generated in a fashion that does not leak user information, e.g.,
randomly or using a per-bundle group counter, and SHOULD be 3 bytes randomly or using a per-bundle group counter, and SHOULD be 3 bytes
or less, to allow them to efficiently fit into the MID RTP header or less, to allow them to efficiently fit into the MID RTP header
extension. Note that if implementations use different methods for extension. Note that if implementations use different methods for
generating identification-tags this could enable fingerprinting of generating identification-tags this could enable fingerprinting of
the implementation making it vulnerable to targeted attacks. The the implementation making it vulnerable to targeted attacks. The
identification-tag is exposed on the RTP stream level when included identification-tag is exposed on the RTP stream level when included
in the RTP header extensions, however what it reveals of the RTP in the RTP header extensions, however what it reveals of the RTP
media stream structure of the endpoint and application was already media stream structure of the endpoint and application was already
possible to deduce from the RTP streams without the MID SDES header possible to deduce from the RTP streams without the MID SDES header
extensions. As the identification-tag is also used to route the extensions. As the identification-tag is also used to route the
media stream to the right application functionality it is also media stream to the right application functionality it is important
important that the value received is the one intended by the sender, that the value received is the one intended by the sender, thus
thus integrity and the authenticity of the source are important to integrity and the authenticity of the source are important to prevent
prevent denial of service on the application. Existing SRTP denial of service on the application. Existing SRTP configurations
configurations and other security mechanisms protecting the whole and other security mechanisms protecting the whole RTP/RTCP packets
RTP/RTCP packets will provide the necessary protection. will provide the necessary protection.
When the BUNDLE extension is used, the set of configurations of the When the BUNDLE extension is used, the set of configurations of the
security mechanism used in all the bundled media descriptions will security mechanism used in all the bundled media descriptions will
need to be compatible so that they can simultaneously used in need to be compatible so that they can be used simultaneously, at
parallel, at least per direction or endpoint. When using SRTP this least per direction or endpoint. When using SRTP this will be the
will be the case, at least for the IETF defined key-management case, at least for the IETF defined key-management solutions due to
solutions due to their SDP attributes (a=crypto, a=fingerprint, their SDP attributes (a=crypto, a=fingerprint, a=mikey) and their
a=mikey) and their classification in classification in [I-D.ietf-mmusic-sdp-mux-attributes].
[I-D.ietf-mmusic-sdp-mux-attributes].
The security considerations of "RTP Header Extension for the RTP The security considerations of "RTP Header Extension for the RTP
Control Protocol (RTCP) Source Description Items" [RFC7941] requires Control Protocol (RTCP) Source Description Items" [RFC7941] requires
that when RTCP is confidentiality protected that any SDES RTP header that when RTCP is confidentiality protected, and that any SDES RTP
extension carrying an SDES item, such as the MID RTP header header extension carrying an SDES item, such as the MID RTP header
extension, is also protected using commensurate strength algorithms. extension, is also protected using commensurate strength algorithms.
However, assuming the above requirements and recommendations are However, assuming the above requirements and recommendations are
followed there are no known significant security risks with leaving followed, there are no known significant security risks with leaving
the MID RTP header extension without confidentiality protection. the MID RTP header extension without confidentiality protection.
Thus, the requirements in RFC 7941 MAY be ignored for the MID RTP Thus, the requirements in RFC 7941 MAY be ignored for the MID RTP
header extension. Security mechanisms for RTP/RTCP are discussed in header extension. Security mechanisms for RTP/RTCP are discussed in
Options for Securing RTP Sessions [RFC7201], for example SRTP Options for Securing RTP Sessions [RFC7201], for example SRTP
[RFC3711] can provide the necessary security functions of ensuring [RFC3711] can provide the necessary security functions of ensuring
the integrity and source authenticity. the integrity and source authenticity.
18. Examples 18. Examples
18.1. Example: Bundle Address Selection 18.1. Example: Bundle Address Selection
skipping to change at page 42, line 45 skipping to change at page 43, line 45
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=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=rtcp-mux
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
18.3. Example: Offerer Adds A Media Description To A BUNDLE Group 18.3. 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 exchange), in which the offerer adds a new previous offer/answer exchange), in which the offerer adds a new
"m=" section, represented by the "zen" identification-tag, to a "m=" section, represented by the "zen" identification-tag, to a
previously negotiated BUNDLE group, assigns the previously previously negotiated BUNDLE group, assigns the previously
selected offerer BUNDLE address to the added "m=" section, selected offerer BUNDLE address to the added "m=" section,
represented by the offerer BUNDLE-tag. To every other bundled represented by the offerer BUNDLE-tag. To every other bundled
"m=" section the offerer assigns a zero port value and includes an "m=" section the offerer assigns a zero port value and includes an
SDP 'bundle-only' attribute. SDP 'bundle-only' attribute.
o An answer, in which the answerer assigns the answerer BUNDLE o An answer, in which the answerer assigns the answerer BUNDLE
address to the bundled "m=" section represented by the answerer address to the bundled "m=" section represented by the answerer
BUNDLE-tag. To every other bundled "m=S section the answerer BUNDLE-tag. To every other bundled "m=" section the answerer
assigns a zero port value and includes an SDP 'bundle-only' assigns a zero port value and includes an SDP 'bundle-only'
attribute. attribute.
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 zen foo bar a=group:BUNDLE zen foo bar
m=audio 0 RTP/AVP 0 8 97 m=audio 0 RTP/AVP 0 8 97
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=bundle-only a=bundle-only
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 0 RTP/AVP 31 32 m=video 0 RTP/AVP 31 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=bundle-only
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 10000 RTP/AVP 66 m=video 10000 RTP/AVP 66
b=AS:1000 b=AS:1000
a=mid:zen a=mid:zen
a=bundle-only
a=rtcp-mux 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 zen foo bar a=group:BUNDLE zen foo bar
m=audio 0 RTP/AVP 0 m=audio 0 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=bundle-only a=bundle-only
skipping to change at page 44, line 17 skipping to change at page 45, line 14
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 zen foo bar a=group:BUNDLE zen foo bar
m=audio 0 RTP/AVP 0 m=audio 0 RTP/AVP 0
b=AS:200 b=AS:200
a=mid:foo a=mid:foo
a=bundle-only a=bundle-only
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 0 RTP/AVP 32 m=video 0 RTP/AVP 32
b=AS:1000 b=AS:1000
a=mid:bar a=mid:bar
a=bundle-only a=bundle-only
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
18.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group 18.4. 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=" section, represented by the "zen" identification-tag, bundled "m=" section, represented by the "zen" identification-tag,
out of a BUNDLE group, assigns a unique address to the moved "m=" out of a BUNDLE group, assigns a unique address to the moved "m="
section, and assigns the previously selected offerer BUNDLE section, and assigns the previously selected offerer BUNDLE
address to another bundled "m=" section, represented by the address to another bundled "m=" section, represented by the
offerer BUNDLE-tag. To every other bundled "m=" section the offerer BUNDLE-tag. To every other bundled "m=" section the
skipping to change at page 46, line 16 skipping to change at page 47, line 12
a=mid:bar a=mid:bar
a=bundle-only a=bundle-only
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=rtcp-mux
a=rtpmap:66 H261/90000 a=rtpmap:66 H261/90000
18.5. Example: Offerer Disables A Media Description Within A BUNDLE 18.5. 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=" section represented by the "zen" identification- a bundled "m=" section represented by the "zen" identification-
tag, within a BUNDLE group, assigns a zero port number to the tag, within a BUNDLE group, assigns a zero port number to the
disabled "m=" section, and assigns the offerer BUNDLE address to disabled "m=" section, and assigns the offerer BUNDLE address to
another bundled "m=" section, represented by the offerer BUNDLE- another bundled "m=" section, represented by the offerer BUNDLE-
skipping to change at page 47, line 46 skipping to change at page 48, line 42
a=bundle-only a=bundle-only
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
19. Acknowledgements 19. 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 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,
skipping to change at page 48, line 30 skipping to change at page 49, line 28
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.
20. Change Log 20. 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-43
o Changes based on WG chairs review.
o Text added in order to close GitHub issues by Taylor B.
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-42 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-42
o Changes based on final WG review. o Changes based on final WG review.
Changes from draft-ietf-mmusic-sdp-bundle-negotiation-41 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-41
o Update to section 6 o RFC 3264: o Update to section 6 o RFC 3264:
o https://github.com/cdh4u/draft-sdp-bundle/pull/47 o https://github.com/cdh4u/draft-sdp-bundle/pull/47
skipping to change at page 58, line 36 skipping to change at page 59, line 36
o Added text about single versus multiple RTP Sessions. o Added text about single versus multiple RTP Sessions.
o Added reference to RFC 3550. o Added reference to RFC 3550.
21. References 21. References
21.1. Normative References 21.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc- DOI 10.17487/RFC2119, March 1997,
editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002, <https://www.rfc- DOI 10.17487/RFC3264, June 2002,
editor.org/info/rfc3264>. <https://www.rfc-editor.org/info/rfc3264>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/info/rfc3550>. July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605, in Session Description Protocol (SDP)", RFC 3605,
DOI 10.17487/RFC3605, October 2003, <https://www.rfc- DOI 10.17487/RFC3605, October 2003,
editor.org/info/rfc3605>. <https://www.rfc-editor.org/info/rfc3605>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004, RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/info/rfc3711>. <https://www.rfc-editor.org/info/rfc3711>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>. July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC4961] Wing, D., "Symmetric RTP / RTP Control Protocol (RTCP)", [RFC4961] Wing, D., "Symmetric RTP / RTP Control Protocol (RTCP)",
BCP 131, RFC 4961, DOI 10.17487/RFC4961, July 2007, BCP 131, RFC 4961, DOI 10.17487/RFC4961, July 2007,
<https://www.rfc-editor.org/info/rfc4961>. <https://www.rfc-editor.org/info/rfc4961>.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, Control Packets on a Single Port", RFC 5761,
DOI 10.17487/RFC5761, April 2010, <https://www.rfc- DOI 10.17487/RFC5761, April 2010,
editor.org/info/rfc5761>. <https://www.rfc-editor.org/info/rfc5761>.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764, Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC5764, May 2010, <https://www.rfc- DOI 10.17487/RFC5764, May 2010,
editor.org/info/rfc5764>. <https://www.rfc-editor.org/info/rfc5764>.
[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, <https://www.rfc- DOI 10.17487/RFC5888, June 2010,
editor.org/info/rfc5888>. <https://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, <https://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7941] Westerlund, M., Burman, B., Even, R., and M. Zanaty, "RTP [RFC7941] Westerlund, M., Burman, B., Even, R., and M. Zanaty, "RTP
Header Extension for the RTP Control Protocol (RTCP) Header Extension for the RTP Control Protocol (RTCP)
Source Description Items", RFC 7941, DOI 10.17487/RFC7941, Source Description Items", RFC 7941, DOI 10.17487/RFC7941,
August 2016, <https://www.rfc-editor.org/info/rfc7941>. August 2016, <https://www.rfc-editor.org/info/rfc7941>.
[RFC8285] Singer, D., Desineni, H., and R. Even, Ed., "A General [RFC8285] Singer, D., Desineni, H., and R. Even, Ed., "A General
Mechanism for RTP Header Extensions", RFC 8285, Mechanism for RTP Header Extensions", RFC 8285,
DOI 10.17487/RFC8285, October 2017, <https://www.rfc- DOI 10.17487/RFC8285, October 2017,
editor.org/info/rfc8285>. <https://www.rfc-editor.org/info/rfc8285>.
[I-D.ietf-ice-rfc5245bis] [I-D.ietf-ice-rfc5245bis]
Keranen, 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-15 (work in progress), November 2017. rfc5245bis-15 (work in progress), November 2017.
[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-16 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-16
skipping to change at page 60, line 33 skipping to change at page 61, line 33
"Session Description Protocol (SDP) Offer/Answer "Session Description Protocol (SDP) Offer/Answer
procedures for Interactive Connectivity Establishment procedures for Interactive Connectivity Establishment
(ICE)", draft-ietf-mmusic-ice-sip-sdp-16 (work in (ICE)", draft-ietf-mmusic-ice-sip-sdp-16 (work in
progress), November 2017. progress), November 2017.
21.2. Informative References 21.2. 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, <https://www.rfc- DOI 10.17487/RFC3261, June 2002,
editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
"RTP Control Protocol Extended Reports (RTCP XR)", "RTP Control Protocol Extended Reports (RTCP XR)",
RFC 3611, DOI 10.17487/RFC3611, November 2003, RFC 3611, DOI 10.17487/RFC3611, November 2003,
<https://www.rfc-editor.org/info/rfc3611>. <https://www.rfc-editor.org/info/rfc3611>.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile "Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
February 2008, <https://www.rfc-editor.org/info/rfc5104>. February 2008, <https://www.rfc-editor.org/info/rfc5104>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
DOI 10.17487/RFC4585, July 2006, <https://www.rfc- DOI 10.17487/RFC4585, July 2006,
editor.org/info/rfc4585>. <https://www.rfc-editor.org/info/rfc4585>.
[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009,
<https://www.rfc-editor.org/info/rfc5576>. <https://www.rfc-editor.org/info/rfc5576>.
[RFC7160] Petit-Huguenin, M. and G. Zorn, Ed., "Support for Multiple [RFC7160] Petit-Huguenin, M. and G. Zorn, Ed., "Support for Multiple
Clock Rates in an RTP Session", RFC 7160, Clock Rates in an RTP Session", RFC 7160,
DOI 10.17487/RFC7160, April 2014, <https://www.rfc- DOI 10.17487/RFC7160, April 2014,
editor.org/info/rfc7160>. <https://www.rfc-editor.org/info/rfc7160>.
[RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP [RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP
Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014, Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,
<https://www.rfc-editor.org/info/rfc7201>. <https://www.rfc-editor.org/info/rfc7201>.
[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and [RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
for Real-Time Transport Protocol (RTP) Sources", RFC 7656, for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
DOI 10.17487/RFC7656, November 2015, <https://www.rfc- DOI 10.17487/RFC7656, November 2015,
editor.org/info/rfc7656>. <https://www.rfc-editor.org/info/rfc7656>.
[I-D.ietf-ice-trickle] [I-D.ietf-ice-trickle]
Ivov, E., Rescorla, E., Uberti, J., and P. Saint-Andre, Ivov, E., Rescorla, E., Uberti, J., and P. Saint-Andre,
"Trickle ICE: Incremental Provisioning of Candidates for "Trickle ICE: Incremental Provisioning of Candidates for
the Interactive Connectivity Establishment (ICE) the Interactive Connectivity Establishment (ICE)
Protocol", draft-ietf-ice-trickle-15 (work in progress), Protocol", draft-ietf-ice-trickle-15 (work in progress),
November 2017. November 2017.
[I-D.ietf-avtext-lrr] [I-D.ietf-avtext-lrr]
Lennox, J., Hong, D., Uberti, J., Holmer, S., and M. Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.
skipping to change at page 62, line 5 skipping to change at page 63, line 5
transport for media specified by the "m=" sections. Issues with both transport for media specified by the "m=" sections. Issues with both
approaches, discussed in the Appendix have been raised. The outcome approaches, discussed in the Appendix have been raised. The outcome
was to specify a mechanism which uses SDP Offers with both different was to specify a mechanism which uses SDP Offers with both different
and identical port values. 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
the "BUNDLE" grouping extension: the "BUNDLE" grouping extension:
o 1) Interoperability with existing UAs. o 1) Interoperability with existing UAs.
o 2) Interoperability with intermediary B2BUA- and proxy entities. o 2) Interoperability with intermediary Back to Back User Agent
(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.
A.1. UA Interoperability A.1. UA Interoperability
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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 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 a later
later invention to RTP and Bob can not assume that Alice supports RFC extension to RTP and Bob can not assume that Alice supports RFC 4961.
4961. This means that Alice may be sending RTP from a different port This means that Alice may be sending RTP from a different port than
than 10000 or 10002 - some implementation simply send the RTP from an 10000 or 10002 - some implementations 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 knows 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 led some SDP
implementations to use the fact that each "m=" section had a implementations to use the fact that each "m=" section had a
different port number to use that port number as an index to find the different 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 correct m line in the SDP. As a result, some implementations that do
support symmetric RTP and ICE still use a SDP data structure where support symmetric RTP and ICE still use an SDP data structure where
SDP with "m=" sections with the same port such as: SDP with "m=" sections with the same port such as:
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 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=" section being considered an SDP error will result in the second "m=" section 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.2. 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=" section In an SDP Offer or SDP Answer, the media specified by an "m=" section
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, This is different from e.g., using the SDP direction attributes,
where RTCP traffic will continue even if the SDP "inactive" attribute where RTCP traffic will continue even if the SDP "inactive" attribute
is indicated for the associated "m=" section. is indicated for the associated "m=" section.
If each "m=" section associated with a BUNDLE group would contain If each "m=" section 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=" sectcion occur if an endpoint wants to disable/reject the "m=" section
associated with that port, by setting the port value to zero. After associated with that port, by setting the port value to zero. After
that, no "m=" section would contain the port value which is used for that, no "m=" section would contain the port value which is used for
the BUNDLE address. In addition, it is unclear what would happen to the BUNDLE address. In addition, it is unclear what would happen to
the ICE candidates associated with the "m=" section, as they are also the ICE candidates associated with the "m=" section, as they are also
used for the BUNDLE address. used for the BUNDLE address.
A.3. 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
skipping to change at page 64, line 26 skipping to change at page 65, line 26
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 49171 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, a B2BUA 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 its 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.3.1. 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 B2BUAs, 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.3.2. 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 B2BUAs, 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=" section, which means that it might not be allocation is done per "m=" section, which means that it might not be
enough if media specified by all "m=" sections try to use that enough if media specified by all "m=" sections 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.4. Candidate Gathering A.4. Candidate Gathering
When using ICE, a candidate needs to be gathered for each port. This When using ICE, a candidate needs to be gathered for each port. This
takes approximately 20 ms extra for each extra "m=" section due to takes approximately 20 ms extra for each extra "m=" section due to
the NAT pacing requirements. All of this gather can be overlapped the NAT pacing requirements. All of this gathering can be overlapped
with other things while for exampe a web-page is loading to minimize with other things while e.g., a web-page is loading to minimize the
the impact. If the client only wants to generate TURN or STUN ICE impact. If the client only wants to generate TURN or STUN ICE
candidates for one of the "m=" lines and then use trickle ICE candidates for one of the "m=" lines and then use trickle ICE
[I-D.ietf-ice-trickle] to get the non host ICE candidates for the [I-D.ietf-ice-trickle] to get the non host ICE candidates for the
rest of the "m=" sections, it MAY do that and will not need any rest of the "m=" sections, 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
allocations 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, it may cause
use of the TURN server but would be quick in the cases where both more use of the TURN server but would be quick in the cases where
sides supported BUNDLE and would fall back to a successful call in both sides supported BUNDLE and would fall back to a successful call
the other cases. in the other cases.
Authors' Addresses Authors' Addresses
Christer Holmberg Christer Holmberg
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
Email: christer.holmberg@ericsson.com Email: christer.holmberg@ericsson.com
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