draft-ietf-mmusic-data-channel-sdpneg-01.txt   draft-ietf-mmusic-data-channel-sdpneg-02.txt 
MMUSIC K. Drage, Ed. MMUSIC K. Drage, Ed.
Internet-Draft M. Makaraju Internet-Draft M. Makaraju
Intended status: Standards Track J. Stoetzer-Bradler Intended status: Standards Track J. Stoetzer-Bradler
Expires: September 10, 2015 Alcatel-Lucent Expires: October 12, 2015 Alcatel-Lucent
R. Ejzak R. Ejzak
J. Marcon J. Marcon
Unaffiliated Unaffiliated
March 9, 2015 April 10, 2015
SDP-based Data Channel Negotiation SDP-based Data Channel Negotiation
draft-ietf-mmusic-data-channel-sdpneg-01 draft-ietf-mmusic-data-channel-sdpneg-02
Abstract Abstract
The Real-Time Communication in WEB-browsers (RTCWeb) working group is The Real-Time Communication in WEB-browsers (RTCWeb) working group is
charged to provide protocols to support direct interactive rich charged to provide protocols to support direct interactive rich
communications using audio, video, and data between two peers' web- communications using audio, video, and data between two peers' web-
browsers. For the support of data communication, the RTCWeb working browsers. For the support of data communication, the RTCWeb working
group has in particular defined the concept of bi-directional data group has in particular defined the concept of bi-directional data
channels over SCTP, where each data channel might be used to channels over SCTP, where each data channel might be used to
transport other protocols, called sub-protocols. Data channel setup transport other protocols, called sub-protocols. Data channel setup
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 10, 2015. This Internet-Draft will expire on October 12, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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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
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
4.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5 5. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Generic External Negotiation . . . . . . . . . . . . . . 6 5.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5
4.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6 5.2. Generic External Negotiation . . . . . . . . . . . . . . 6
4.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6 5.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6
4.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 7 5.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6
5. SDP-based External Negotiation . . . . . . . . . . . . . . . 7 5.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 7
5.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 8 6. SDP-based External Negotiation . . . . . . . . . . . . . . . 8
5.1.1. SDP Attribute for Data Channel Parameter Negotiation 8 6.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 8
5.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 8 6.1.1. SDP Attribute for Data Channel Parameter Negotiation 8
5.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 10 6.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 8
5.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 10 6.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 10
5.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 10 6.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 10
5.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 10 6.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 10
5.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 10 6.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 10
5.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 11 6.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 11
5.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 11 6.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 11
5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12 6.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 11
5.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 12 6.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13 6.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 13
5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14 6.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13
5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16 6.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 17 6.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.2.5. Various SDP Offer/Answer Scenarios and Considerations 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.1. Subprotocol identifiers . . . . . . . . . . . . . . . . . 20
10.1. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 21 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
10.2. Changes against 'draft-ejzak-mmusic-data-channel- 11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 24 11.1. Changes against 'draft-ietf-mmusic-data-channel-
10.3. Changes against '-01' . . . . . . . . . . . . . . . . . 25 sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 21
10.4. Changes against '-00' . . . . . . . . . . . . . . . . . 25 11.2. Changes against 'draft-ietf-mmusic-data-channel-
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 23
11.1. Normative References . . . . . . . . . . . . . . . . . . 25 11.3. Changes against 'draft-ejzak-mmusic-data-channel-
11.2. Informative References . . . . . . . . . . . . . . . . . 26 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 11.4. Changes against '-01' . . . . . . . . . . . . . . . . . 27
11.5. Changes against '-00' . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
12.1. Normative References . . . . . . . . . . . . . . . . . . 28
12.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
The RTCWeb working group has defined the concept of bi-directional The RTCWeb working group has defined the concept of bi-directional
data channels running on top of SCTP/DTLS. RTCWeb leaves it open for data channels running on top of SCTP/DTLS. RTCWeb leaves it open for
other applications to use data channels and its in-band or out-of- other applications to use data channels and its in-band or out-of-
band protocol for creating them. Each data channel consists of band protocol for creating them. Each data channel consists of
paired SCTP streams sharing the same SCTP Stream Identifier. Data paired SCTP streams sharing the same SCTP Stream Identifier. Data
channels are created by endpoint applications through the WebRTC API, channels are created by endpoint applications through the WebRTC API,
or other users of data channel like CLUE, and can be used to or other users of data channel like CLUE, and can be used to
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Out-of-band: transmission through the application signaling path. Out-of-band: transmission through the application signaling path.
Peer: From the perspective of one of the agents in a session, its Peer: From the perspective of one of the agents in a session, its
peer is the other agent. Specifically, from the perspective of peer is the other agent. Specifically, from the perspective of
the SDP offerer, the peer is the SDP answerer. From the the SDP offerer, the peer is the SDP answerer. From the
perspective of the SDP answerer, the peer is the SDP offerer. perspective of the SDP answerer, the peer is the SDP offerer.
Stream identifier: the identifier of the outbound and inbound SCTP Stream identifier: the identifier of the outbound and inbound SCTP
streams composing a data channel. streams composing a data channel.
4. Data Channels 4. Applicability Statement
The mechanism in this specification only applies to the Session
Description Protocol (SDP) [RFC4566], when used together with the SDP
offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of
scope of this document, and is thus undefined.
5. Data Channels
This section summarizes how data channels work in general. Note that This section summarizes how data channels work in general. Note that
the references to 'browser' here is intentional as in this specific the references to 'browser' here is intentional as in this specific
example the data channel user is a Webrtc enabled browser. example the data channel user is a Webrtc enabled browser.
A WebRTC application creates a data channel via the data channel API, A WebRTC application creates a data channel via the data channel API,
by providing a number of setup parameters (sub-protocol, label, by providing a number of setup parameters (sub-protocol, label,
reliability, order of delivery, priority). The application also reliability, order of delivery, priority). The application also
specifies if it wants to make use of the in-band negotiation using specifies if it wants to make use of the in-band negotiation using
the DCEP [I-D.ietf-rtcweb-data-protocol], or if the application the DCEP [I-D.ietf-rtcweb-data-protocol], or if the application
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4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
Note: A WebRTC browser will only use "m" line format "webrtc- Note: A WebRTC browser will only use "m" line format "webrtc-
datachannel", and will not use other formats in the "m" line for datachannel", and will not use other formats in the "m" line for
other protocols such as t38. [I-D.ietf-mmusic-sctp-sdp] supports other protocols such as t38. [I-D.ietf-mmusic-sctp-sdp] supports
only one SCTP association to be established on top of a DTLS session. only one SCTP association to be established on top of a DTLS session.
Note: This SDP syntax does not contain any channel-specific Note: This SDP syntax does not contain any channel-specific
information. information.
4.1. Stream Identifier Numbering 5.1. Stream Identifier Numbering
Independently from the requested type of negotiation, the application Independently from the requested type of negotiation, the application
creating a data channel can either pass to the browser the stream creating a data channel can either pass to the browser the stream
identifier to assign to the data channel or else let the browser pick identifier to assign to the data channel or else let the browser pick
one identifier from the ones unused. one identifier from the ones unused.
To avoid glare situations, each endpoint can moreover own an To avoid glare situations, each endpoint can moreover own an
exclusive set of stream identifiers, in which case an endpoint can exclusive set of stream identifiers, in which case an endpoint can
only create a data channel with a stream identifier it owns. only create a data channel with a stream identifier it owns.
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determined by convention or other means. determined by convention or other means.
For data channels negotiated in-band, one endpoint owns by For data channels negotiated in-band, one endpoint owns by
convention the even stream identifiers, whereas the other owns the convention the even stream identifiers, whereas the other owns the
odd stream identifiers, as defined in odd stream identifiers, as defined in
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
For data channels externally negotiated, no convention is defined For data channels externally negotiated, no convention is defined
by default. by default.
4.2. Generic External Negotiation 5.2. Generic External Negotiation
4.2.1. Overview 5.2.1. Overview
In-band negotiation only provides for negotiation of data channel In-band negotiation only provides for negotiation of data channel
transport parameters and does not provide for negotiation of sub- transport parameters and does not provide for negotiation of sub-
protocol specific parameters. External negotiation can be defined to protocol specific parameters. External negotiation can be defined to
allow negotiation of parameters beyond those handled by in-band allow negotiation of parameters beyond those handled by in-band
negotiation, e.g., parameters specific to the sub-protocol negotiation, e.g., parameters specific to the sub-protocol
instantiated on a particular data channel. See Section 5.1.2 for an instantiated on a particular data channel. See Section 6.1.2 for an
example of such a parameter. example of such a parameter.
The following procedures are common to all methods of external The following procedures are common to all methods of external
negotiation, whether in-band (communicated using proprietary means on negotiation, whether in-band (communicated using proprietary means on
an already established data channel) or out-of-band (using SDP or an already established data channel) or out-of-band (using SDP or
some other protocol associated with the signaling channel). some other protocol associated with the signaling channel).
4.2.2. Opening a Data Channel 5.2.2. Opening a Data Channel
In the case of external negotiation, the endpoint application has the In the case of external negotiation, the endpoint application has the
option to fully control the stream identifier assignments. However option to fully control the stream identifier assignments. However
these assignments have to coexist with the assignments controlled by these assignments have to coexist with the assignments controlled by
the data channel stack for the in-band negotiated data channels (if the data channel stack for the in-band negotiated data channels (if
any). It is the responsibility of the application to ensure any). It is the responsibility of the application to ensure
consistent assignment of stream identifiers. consistent assignment of stream identifiers.
When the application requests the creation of a new data channel to When the application requests the creation of a new data channel to
be set up via external negotiation, the data channel stack creates be set up via external negotiation, the data channel stack creates
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It is also worth noting that a data channel stack implementation may It is also worth noting that a data channel stack implementation may
not provide any API to create and close data channels; instead the not provide any API to create and close data channels; instead the
data channels are used on the fly as needed just by communicating via data channels are used on the fly as needed just by communicating via
external means or by even having some local configuration/assumptions external means or by even having some local configuration/assumptions
on both the peers. on both the peers.
The application then externally negotiates the data channel The application then externally negotiates the data channel
properties and sub-protocol properties with the peer's application. properties and sub-protocol properties with the peer's application.
[ASSUMPTION] The peer must then symmetrically create a data channel [ASSUMPTION] The peer MUST then symmetrically create a data channel
with these negotiated data channel properties. This is the only way with these negotiated data channel properties. This is the only way
for the peer's data channel stack to know which properties to apply for the peer's data channel stack to know which properties to apply
when transmitting data on this channel. The data channel stack must when transmitting data on this channel. The data channel stack MUST
allow data channel creation with any non-conflicting stream allow data channel creation with any non-conflicting stream
identifier so that both peers can create the data channel with the identifier so that both peers can create the data channel with the
same stream identifier. same stream identifier.
In case the external negotiation is correlated with an SDP offer/ In case the external negotiation is correlated with an SDP offer/
answer exchange that establishes the SCTP association, the SCTP answer exchange that establishes the SCTP association, the SCTP
initialization completion triggers a callback from the data channel initialization completion triggers a callback from the data channel
stack to an application on both the ends to change the data channel stack to an application on both the ends to change the data channel
state from Connecting to Open. The details of this interface is state from Connecting to Open. The details of this interface is
specific to the data channel user application. Browser based specific to the data channel user application. Browser based
applications (could include hybrid apps) will use [WebRtcAPI], while applications (could include hybrid apps) will use [WebRtcAPI], while
native applications use a compatible API, which is yet to be native applications use a compatible API, which is yet to be
specified. See Section 5.2.3 for details on when the data channel specified. See Section 6.2.3 for details on when the data channel
stack can assume the data channel is open, and on when the stack can assume the data channel is open, and on when the
application can assume the data channel is open. application can assume the data channel is open.
4.2.3. Closing a Data Channel 5.2.3. Closing a Data Channel
When the application requests the closing of an externally negotiated When the application requests the closing of an externally negotiated
data channel, the data channel stack always performs an in-band SSN data channel, the data channel stack always performs an in-band SSN
reset for this channel. reset for this channel.
Depending upon the method used for external negotiation and the sub- Depending upon the method used for external negotiation and the sub-
protocol associated with the data channel, the closing might in protocol associated with the data channel, the closing might in
addition be signaled to the peer via external negotiation. addition be signaled to the peer via external negotiation.
5. SDP-based External Negotiation 6. SDP-based External Negotiation
This section defines a method of external negotiation by which two This section defines a method of external negotiation by which two
clients can negotiate data channel-specific and sub-protocol-specific clients can negotiate data channel-specific and sub-protocol-specific
parameters, using the out-of-band SDP offer/answer exchange. This parameters, using the out-of-band SDP offer/answer exchange. This
SDP extension can only be used with SDP offer/answer model. SDP extension can only be used with SDP offer/answer model.
5.1. SDP Syntax 6.1. SDP Syntax
Two new SDP attributes are defined to support external negotiation of Two new SDP attributes are defined to support external negotiation of
data channels. The first attribute provides for negotiation of data channels. The first attribute provides for negotiation of
channel-specific parameters. The second attribute provides for channel-specific parameters. The second attribute provides for
negotiation of sub-protocol-specific parameters. negotiation of sub-protocol-specific parameters.
5.1.1. SDP Attribute for Data Channel Parameter Negotiation 6.1.1. SDP Attribute for Data Channel Parameter Negotiation
Associated with the SDP "m" line that defines the SCTP association Associated with the SDP "m" line that defines the SCTP association
for data channels (defined in Section 4), each SDP offer and answer for data channels (defined in Section 4), each SDP offer and answer
includes one "a=dcmap:" attribute that defines the data channel includes one "a=dcmap:" attribute that defines the data channel
parameters for each data channel to be negotiated. Each such parameters for each data channel to be negotiated. Each such
attribute line specifies the following parameters for a data channel: attribute line specifies the following parameters for a data channel:
SCTP stream identifier, sub-protocol, label, reliability, order of SCTP stream identifier, sub-protocol, label, reliability, order of
delivery, and priority. delivery, and priority.
The intention of exchanging these attributes is to create data The intention of exchanging these attributes is to create data
channels on both the peers with the same set of attributes without channels on both the peers with the same set of attributes without
actually using [I-D.ietf-rtcweb-data-protocol]. It is assumed that actually using [I-D.ietf-rtcweb-data-protocol]. It is assumed that
the data channel properties (reliable/partially reliable, ordered/ the data channel properties (reliable/partially reliable, ordered/
unordered) are suitable per the sub-protocol transport requirements. unordered) are suitable per the sub-protocol transport requirements.
5.1.1.1. dcmap Attribute 6.1.1.1. dcmap Attribute
"a=dcmap:" is a media level attribute having following ABNF syntax. "a=dcmap:" is a media level attribute having following ABNF syntax.
Formal Syntax: Formal Syntax:
Name: dcmap Name: dcmap
Value: dcmap-value Value: dcmap-value
Usage Level: media Usage Level: media
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Charset Dependent: no Charset Dependent: no
Syntax: Syntax:
dcmap-value = dcmap-stream-id dcmap-value = dcmap-stream-id
[ SP dcmap-opt *(";" dcmap-opt) ] [ SP dcmap-opt *(";" dcmap-opt) ]
dcmap-opt = ordering-opt / subprotocol-opt / label-opt dcmap-opt = ordering-opt / subprotocol-opt / label-opt
/ maxretr-opt / maxtime-opt / maxretr-opt / maxtime-opt
; Either only maxretr-opt or maxtime-opt ; Either only maxretr-opt or maxtime-opt
; is present. ; is present.
; Both MUST not be present.
dcmap-stream-id = 1*DIGIT dcmap-stream-id = 1*DIGIT
ordering-opt = "ordered=" ordering-value ordering-opt = "ordered=" ordering-value
ordering-value = "true" / "false" ordering-value = "true" / "false"
subprotocol-opt = "subprotocol=" quoted-string subprotocol-opt = "subprotocol=" quoted-string
label-opt = "label=" quoted-string label-opt = "label=" quoted-string
maxretr-opt = "max-retr=" maxretr-value maxretr-opt = "max-retr=" maxretr-value
maxretr-value = <from-Reliability-Parameter of maxretr-value = <from-Reliability-Parameter of
I-D.ietf-rtcweb-data-protocol> I-D.ietf-rtcweb-data-protocol>
; number of retransmissions ; number of retransmissions
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a=dcmap:0 a=dcmap:0
a=dcmap:1 subprotocol="BFCP";max-time=60000 a=dcmap:1 subprotocol="BFCP";max-time=60000
a=dcmap:2 subprotocol="MSRP";ordered=true;label="MSRP" a=dcmap:2 subprotocol="MSRP";ordered=true;label="MSRP"
a=dcmap:3 label="Label 1";ordered=false;max-retr=5 a=dcmap:3 label="Label 1";ordered=false;max-retr=5
a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000;max-retr=3 a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000;max-retr=3
Note: The last example (a=dcmap:4) shows a 'label' parameter value Note: The last example (a=dcmap:4) shows a 'label' parameter value
which contains one non-printable 'escaped-char' character (the which contains one non-printable 'escaped-char' character (the
tabulator character). tabulator character).
5.1.1.2. dcmap-stream-id Parameter Within an 'a=dcmap' attribute line's 'dcmap-opt' value either only
one 'maxretr-opt' parameter or one 'maxtime-opt' parameter is
present. Both MUST NOT be present.
6.1.1.2. dcmap-stream-id Parameter
The 'dcmap-stream-id' parameter indicates the SCTP stream identifier The 'dcmap-stream-id' parameter indicates the SCTP stream identifier
within the SCTP association used to form the data channel. within the SCTP association used to form the data channel.
5.1.1.3. label Parameter 6.1.1.3. label Parameter
The 'label' parameter indicates the name of the channel. It The 'label' parameter indicates the name of the channel. It
represents a label that can be used to distinguish, in the context of represents a label that can be used to distinguish, in the context of
the WebRTC API, an RTCDataChannel object from other RTCDataChannel the WebRTC API, an RTCDataChannel object from other RTCDataChannel
objects. This parameter maps to the 'Label' parameter defined in objects. This parameter maps to the 'Label' parameter defined in
[I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is optional. [I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is optional.
If it is not present, then its value defaults to the empty string. If it is not present, then its value defaults to the empty string.
Note: The empty string may also be explicitly used as 'label' value, Note: The empty string may also be explicitly used as 'label' value,
such that 'label=""' is equivalent to the 'label' parameter not being such that 'label=""' is equivalent to the 'label' parameter not being
present at all. [I-D.ietf-rtcweb-data-protocol] allows the present at all. [I-D.ietf-rtcweb-data-protocol] allows the
DATA_CHANNEL_OPEN message's 'Label' value to be an empty string. DATA_CHANNEL_OPEN message's 'Label' value to be an empty string.
5.1.1.4. subprotocol Parameter 6.1.1.4. subprotocol Parameter
The 'subprotocol' parameter indicates which protocol the client The 'subprotocol' parameter indicates which protocol the client
expects to exchange via the channel. 'Subprotocol' is an optional expects to exchange via the channel. 'Subprotocol' is an optional
parameter. If the 'subprotocol' parameter is not present, then its parameter. If the 'subprotocol' parameter is not present, then its
value defaults to the empty string. value defaults to the empty string.
5.1.1.5. max-retr Parameter 6.1.1.5. max-retr Parameter
This parameter indicates that the data channel is partially reliable. This parameter indicates that the data channel is partially reliable.
The 'max-retr' parameter indicates the max times a user message will The 'max-retr' parameter indicates the max times a user message will
be retransmitted. The max-retr parameter is optional. If the max- be retransmitted. The max-retr parameter is optional. If the max-
retr parameter is not present, then the maximal number of retr parameter is not present, then the maximal number of
retransmissions is determined as per the generic SCTP retransmission retransmissions is determined as per the generic SCTP retransmission
rules as specified in [RFC4960]. This parameter maps to the 'Number rules as specified in [RFC4960]. This parameter maps to the 'Number
of RTX' parameter defined in [I-D.ietf-rtcweb-data-protocol]. of RTX' parameter defined in [I-D.ietf-rtcweb-data-protocol].
5.1.1.6. max-time Parameter 6.1.1.6. max-time Parameter
This parameter indicates that the data channel is partially reliable. This parameter indicates that the data channel is partially reliable.
A user message will no longer be transmitted or retransmitted after a A user message will no longer be transmitted or retransmitted after a
specified life-time given in milliseconds in the 'max-time' specified life-time given in milliseconds in the 'max-time'
parameter. The max-time parameter is optional. If the max-time parameter. The max-time parameter is optional. If the max-time
parameter is not present, then the generic SCTP retransmission timing parameter is not present, then the generic SCTP retransmission timing
rules apply as specified in [RFC4960]. This parameter maps to the rules apply as specified in [RFC4960]. This parameter maps to the
'Lifetime in ms' parameter defined in 'Lifetime in ms' parameter defined in
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
5.1.1.7. ordered Parameter 6.1.1.7. ordered Parameter
The 'ordered' parameter with value "true" indicates that DATA chunks The 'ordered' parameter with value "true" indicates that the receiver
in the channel MUST be dispatched to the upper layer by the receiver MUST dispatch DATA chunks in the data channel to the upper layer
while preserving the order. The ordered parameter is optional and while preserving the order. The ordered parameter is optional and
takes two values: "true" for ordered and "false" for unordered takes two values: "true" for ordered and "false" for unordered
delivery with "true" as the default value. Any other value is delivery with "true" as the default value. Any other value is
ignored and default "ordered=true" is assumed. In the absence of ignored and default "ordered=true" is assumed. In the absence of
this parameter "ordered=true" is assumed. This parameter maps to the this parameter "ordered=true" is assumed. This parameter maps to the
ordered or unordered data channel types as defined in ordered or unordered data channel types as defined in
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
5.1.2. Sub-Protocol Specific Attributes 6.1.2. Sub-Protocol Specific Attributes
In the SDP, each data channel declaration MAY also be followed by In the SDP, each data channel declaration MAY also be followed by
other SDP attributes specific to the sub-protocol in use. Each of other SDP attributes specific to the sub-protocol in use. Each of
these attributes is represented by one new attribute line, and it these attributes is represented by one new attribute line, and it
includes the contents of a media-level SDP attribute already defined includes the contents of a media-level SDP attribute already defined
for use with this (sub)protocol in another IETF specification. Sub- for use with this (sub)protocol in another IETF specification. Sub-
protocol-specific attributes might also be defined for exclusive use protocol-specific attributes might also be defined for exclusive use
with data channel transport, but should use the same syntax described with data channel transport, but should use the same syntax described
here for other sub-protocol-specific attributes. here for other sub-protocol-specific attributes.
skipping to change at page 12, line 24 skipping to change at page 12, line 24
Syntax: Syntax:
dcsa-value = stream-id SP attribute dcsa-value = stream-id SP attribute
attribute = <from-RFC4566> attribute = <from-RFC4566>
Example: Example:
a=dcsa:2 accept-types:text/plain a=dcsa:2 accept-types:text/plain
Note that the above reference to RFC 4566 defines were the attribute
definition can be found; it does not provide any limitation on
support of attributes defined in other documents in accordance with
this attribute definition.
Thus in the example above, the original attribute line "a=accept- Thus in the example above, the original attribute line "a=accept-
types:text/plain" is represented by the attribute line "a=dcsa:2 types:text/plain" is represented by the attribute line "a=dcsa:2
accept-types:text/plain", which specifies that this instance of MSRP accept-types:text/plain", which specifies that this instance of MSRP
being transported on the sctp association using the data channel with being transported on the sctp association using the data channel with
stream id 2 accepts plain text files. stream id 2 accepts plain text files.
As opposed to the data channel "a=dcmap:" attribute parameters, these As opposed to the data channel "a=dcmap:" attribute parameters, these
parameters are subject to offer/answer negotiation following the parameters are subject to offer/answer negotiation following the
procedures defined in the sub-protocol specific documents. procedures defined in the sub-protocol specific documents.
The same syntax applies to any other SDP attribute required for The same syntax applies to any other SDP attribute required for
negotiation of this instance of the sub-protocol. negotiation of this instance of the sub-protocol.
Note: This document does not provide a complete specification of how Note: This document does not provide a complete specification of how
to negotiate the use of a data channel to transport MSRP. Procedures to negotiate the use of a data channel to transport MSRP. Procedures
specific to each sub-protocol such as MSRP will be documented specific to each sub-protocol such as MSRP will be documented
elsewhere. The use of MSRP is only an example of how the generic elsewhere. The use of MSRP is only an example of how the generic
procedures described herein might apply to a specific sub-protocol. procedures described herein might apply to a specific sub-protocol.
5.2. Procedures 6.2. Procedures
6.2.1. Managing Stream Identifiers
5.2.1. Managing Stream Identifiers
If an SDP offer / answer exchange (could be the initial or a If an SDP offer / answer exchange (could be the initial or a
subsequent one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based subsequent one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based
media description being accepted, and if this SDP offer / answer media description being accepted, and if this SDP offer / answer
exchange results in the establishment of a new SCTP association, then exchange results in the establishment of a new SCTP association, then
the SDP offerer owns the even SCTP stream ids of this new SCTP the SDP offerer owns the even SCTP stream ids of this new SCTP
association and the answerer owns the odd SCTP stream identifiers. association and the answerer owns the odd SCTP stream identifiers.
If this "m" line is removed from the signaling session (its port If this "m" line is removed from the signaling session (its port
number set to zero), and if usage of this or of a new UDP/DTLS/SCTP number set to zero), and if usage of this or of a new UDP/DTLS/SCTP
or TCP/DTLS/SCTP based "m" line is renegotiated later on, then the or TCP/DTLS/SCTP based "m" line is renegotiated later on, then the
even and odd SCTP stream identifier ownership is redetermined as well even and odd SCTP stream identifier ownership is redetermined as well
as described above. as described above.
This specification allows simultaneous use of external and internal This specification allows simultaneous use of external and internal
negotiation. However, a single stream is managed using one method at negotiation. However, a single stream is managed using one method at
a time. Stream ids that are not currently used in SDP can be used a time. Stream ids that are not currently used in SDP can be used
for internal negotiation. Stream id allocation per SDP based for internal negotiation. Stream id allocation per SDP based
skipping to change at page 13, line 26 skipping to change at page 13, line 33
This could cause glare conditions when one side trying to do external This could cause glare conditions when one side trying to do external
negotiation on a stream id while the other end trying to open a data negotiation on a stream id while the other end trying to open a data
channel on the same stream id using internal negotiation. To avoid channel on the same stream id using internal negotiation. To avoid
these glare conditions this specification recommends that the data these glare conditions this specification recommends that the data
channel stack user always selects stream ids per above described SDP channel stack user always selects stream ids per above described SDP
offer / answer rule even when internal negotiation is used. To avoid offer / answer rule even when internal negotiation is used. To avoid
glare conditions, it is possible to come up with a different stream glare conditions, it is possible to come up with a different stream
id allocation scheme, but such schemes are outside the scope of this id allocation scheme, but such schemes are outside the scope of this
specification. specification.
5.2.2. Negotiating Data Channel Parameters 6.2.2. Negotiating Data Channel Parameters
Conveying a reliable data channel is achieved by including neither Conveying a reliable data channel is achieved by including neither
'max-retr' nor 'max-time' in corresponding SDP offer's or answer's 'max-retr' nor 'max-time' in corresponding SDP offer's or answer's
a=dcmap attribute line. Conveying a partially reliable data channel a=dcmap attribute line. Conveying a partially reliable data channel
is achieved by including only one of 'max-retr' or 'max-time'. By is achieved by including only one of 'max-retr' or 'max-time'. By
definition max-retr and max-time are mutually exclusive, so only one definition max-retr and max-time are mutually exclusive, so only one
of them can be present in a=dcmap. If an SDP offer contains both of of them can be present in a=dcmap. If an SDP offer contains both of
these parameters then such an SDP offer will be rejected. If an SDP these parameters then the receiver of such an SDP offer MUST reject
answer contains both of these parameters then the offerer may treat the SDP offer. If an SDP answer contains both of these parameters
it as an error and may assume the associated SDP offer/answer failed then the offerer MAY treat it as an error and MAY assume the
and may take appropriate recovery actions. These recovery options associated SDP offer/answer failed and MAY take appropriate recovery
are outside the scope of this specification. actions. These recovery options are outside the scope of this
specification.
The SDP answer shall echo the same subprotocol, max-retr, max-time, The SDP answer SHALL echo the same subprotocol, max-retr, max-time,
ordered parameters, if those were present in the offer, and may ordered parameters, if those were present in the offer, and MAY
include a label parameter. They may appear in any order, which could include a label parameter. They MAY appear in any order, which could
be different from the SDP offer, in the SDP answer. be different from the SDP offer, in the SDP answer.
The same information MUST be replicated without changes in any When sending a subsequent offer or an answer, and for as long as the
subsequent offer or answer, as long as the data channel is still data channel is still open, the sender MUST replicate the same
opened at the time of offer or answer generation. information.
Data channel types defined in [I-D.ietf-rtcweb-data-protocol] are Data channel types defined in [I-D.ietf-rtcweb-data-protocol] are
mapped to SDP in the following manner: mapped to SDP in the following manner, where "ordered=true" is the
default and may be omitted:
DATA_CHANNEL_RELIABLE DATA_CHANNEL_RELIABLE
a=dcmap:2 subprotocol="BFCP";label="channel 2" ordered=true
DATA_CHANNEL_RELIABLE_UNORDERED DATA_CHANNEL_RELIABLE_UNORDERED
a=dcmap:2 subprotocol="BFCP";label="channel 2";\ ordered=false
ordered=0
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT
a=dcmap:2 subprotocol="BFCP";label="channel 2";\ ordered=true;max-retr=<number of retransmissions>
max-retr=3
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED
a=dcmap:2 subprotocol="BFCP";label="channel 2";\ ordered=false;max-retr=<number of retransmissions>
max-retr=3;ordered=0;
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED
a=dcmap:2 subprotocol="BFCP";label="channel 2";\ ordered=true;max-time=<lifetime in milliseconds>
max-time=10000;
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED
a=dcmap:2 subprotocol="BFCP";label="channel 2";\ ordered=false;max-time=<lifetime in milliseconds>
max-time=10000; ordered=0
5.2.3. Opening a Data Channel 6.2.3. Opening a Data Channel
The procedure for opening a data channel using external negotiation The procedure for opening a data channel using external negotiation
starts with the agent preparing to send an SDP offer. If a peer starts with the agent preparing to send an SDP offer. If a peer
receives an SDP offer before getting to send a new SDP offer with receives an SDP offer before getting to send a new SDP offer with
data channels that are to be externally negotiated, or loses an SDP data channels that are to be externally negotiated, or loses an SDP
offer glare resolution procedure in this case, it must wait until the offer glare resolution procedure in this case, it MUST wait until the
ongoing SDP offer/answer completes before resuming the external ongoing SDP offer/answer completes before resuming the external
negotiation procedure. negotiation procedure.
The agent that intends to send an SDP offer to create data channels The agent that intends to send an SDP offer to create data channels
through SDP-based external negotiation performs the following: through SDP-based external negotiation performs the following:
o Creates data channels using stream identifiers from the owned set o Creates data channels using stream identifiers from the owned set
(see Section 5.2.1). (see Section 6.2.1).
o As described in Section 4.2.2, if the SCTP association is not yet o As described in Section 5.2.2, if the SCTP association is not yet
established, then the newly created data channels are in the established, then the newly created data channels are in the
Connecting state, else if the SCTP association is already Connecting state, else if the SCTP association is already
established, then the newly created data channels are in the Open established, then the newly created data channels are in the Open
state. state.
o Generates a new SDP offer. In the case of the browser based o Generates a new SDP offer. In the case of browser based
applications the browser generates the offer via the createOffer() applications the browser generates the offer via the createOffer()
API call [I-D.ietf-rtcweb-jsep]. API call [I-D.ietf-rtcweb-jsep].
o Determines the list of stream identifiers assigned to data o Determines the list of stream identifiers assigned to data
channels opened through external negotiation. channels opened through external negotiation.
o Completes the SDP offer with the dcmap and dcsa attributes needed, o Completes the SDP offer with the dcmap and dcsa attributes needed,
if any, for each externally-negotiated data channel, as described if any, for each externally-negotiated data channel, as described
in Section 5.1 and in Section 5.2.2. in Section 6.1 and in Section 6.2.2.
o Sends the SDP offer. o Sends the SDP offer.
The peer receiving such an SDP offer performs the following: The peer receiving such an SDP offer performs the following:
o Parses and applies the SDP offer. Note that the typical parser o Parses and applies the SDP offer. Note that the typical parser
normally ignores unknown SDP attributes, which includes data normally ignores unknown SDP attributes, which includes data
channel related attributes. channel related attributes.
o Analyzes the channel parameters and sub-protocol attributes to o Analyzes the channel parameters and sub-protocol attributes to
determine whether to accept each offered data channel. determine whether to accept each offered data channel.
o For accepted data channels, it creates peer instances for the data o For accepted data channels, it creates peer instances for the data
channels with the agent using the channel parameters described in channels with the agent using the channel parameters described in
the SDP offer. Note that the agent is asked to create data the SDP offer. Note that the agent is asked to create data
channels with SCTP stream identifiers contained in the SDP offer channels with SCTP stream identifiers contained in the SDP offer
if the SDP offer is accepted. if the SDP offer is accepted.
o As described in Section 4.2.2, if the SCTP association is not yet o As described in Section 5.2.2, if the SCTP association is not yet
established, then the newly created data channels are in the established, then the newly created data channels are in the
Connecting state, else if the SCTP association is already Connecting state, else if the SCTP association is already
established, then the newly created data channels are in the Open established, then the newly created data channels are in the Open
state. state.
o Generates an SDP answer. o Generates an SDP answer.
o Completes the SDP answer with the dcmap and optional dcsa o Completes the SDP answer with the dcmap and optional dcsa
attributes needed for each externally-negotiated data channel, as attributes needed for each externally-negotiated data channel, as
described in Section 5.1 and in Section 5.2.2. described in Section 6.1 and in Section 6.2.2.
o Sends the SDP answer. o Sends the SDP answer.
The agent receiving such an SDP answer performs the following: The agent receiving such an SDP answer performs the following:
o Closes any created data channels (whether in Connecting or Open o Closes any created data channels (whether in Connecting or Open
state) for which the expected dcmap and dcsa attributes are not state) for which the expected dcmap and dcsa attributes are not
present in the SDP answer. present in the SDP answer.
o Applies the SDP answer. o Applies the SDP answer.
skipping to change at page 16, line 26 skipping to change at page 16, line 31
established SCTP association, as soon as it creates an externally established SCTP association, as soon as it creates an externally
negotiated data channel in the Open state based on information negotiated data channel in the Open state based on information
signaled in the SDP offer. signaled in the SDP offer.
o At the agent sending an SDP offer to create a new externally o At the agent sending an SDP offer to create a new externally
negotiated data channel for which there is an established SCTP negotiated data channel for which there is an established SCTP
association, when it receives the SDP answer confirming acceptance association, when it receives the SDP answer confirming acceptance
of the data channel or when it begins to receive data on the data of the data channel or when it begins to receive data on the data
channel from the peer, whichever occurs first. channel from the peer, whichever occurs first.
5.2.4. Closing a Data Channel 6.2.4. Closing a Data Channel
When the application requests the closing of a data channel that was When the application requests the closing of a data channel that was
externally negotiated, the data channel stack always performs an in- externally negotiated, the data channel stack always performs an in-
band SSN reset for this channel. band SSN reset for this channel.
It is specific to the sub-protocol whether this closing must in It is specific to the sub-protocol whether this closing MUST in
addition be signaled to the peer via a new SDP offer/answer exchange. addition be signaled to the peer via a new SDP offer/answer exchange.
The intention to close a data channel can be signaled by sending a The intention to close a data channel can be signaled by sending a
new SDP offer which excludes the "a=dcmap:" and "a=dcsa:" attribute new SDP offer which excludes the "a=dcmap:" and "a=dcsa:" attribute
lines for the data channel. The port value for the "m" line SHOULD lines for the data channel. The offerer SHOULD NOT change the port
not be changed (e.g., to zero) when closing a data channel (unless value for the "m" line (e.g. to zero) when closing a data channel
all data channels are being closed and the SCTP association is no (unless all data channels are being closed and the SCTP association
longer needed), since this would close the SCTP association and is no longer needed), since this would close the SCTP association and
impact all of the data channels. If the answerer accepts the SDP impact all of the data channels. If the answerer accepts the SDP
offer then it MUST close those data channels whose "a=dcmap:" and offer then the answerer MUST close those data channels whose
"a=dcsa:" attribute lines were excluded from the received SDP offer, "a=dcmap:" and "a=dcsa:" attribute lines were excluded from the
unless those data channels were already closed, and it MUST also received SDP offer, unless those data channels were already closed,
exclude the corresponding attribute lines in the answer. In addition and the answerer MUST also exclude the corresponding attribute lines
to that, the SDP answerer MAY exclude other data channels which were in the answer. In addition to that, the SDP answerer MAY exclude
closed but not yet communicated to the peer. So, the offerer MUST other data channels which were closed but not yet communicated to the
inspect the answer to see if it has to close other data channels peer. So, the offerer MUST inspect the answer to see if it has to
which are now not included in the answer. close other data channels which are now not included in the answer.
If a new SDP offer/answer is used to close data channels then the If a new SDP offer/answer is used to close data channels then the
data channel(s) SHOULD only be closed by the answerer/offerer after a data channel(s) SHOULD only be closed by the answerer/offerer after a
successful SDP answer is sent/received. successful SDP answer is sent/received.
This delayed closure is RECOMMENDED in order to handle cases where This delayed closure is RECOMMENDED in order to handle cases where
a successful SDP answer is not received, in which case the state a successful SDP answer is not received, in which case the state
of the session SHOULD be kept per the last successful SDP offer/ of the session SHOULD be kept per the last successful SDP offer/
answer. answer.
If a client receives a data channel close indication (due to inband If a client receives a data channel close indication (due to inband
SSN reset or some other reason) without associated SDP offer then an SSN reset or some other reason) without associated SDP offer then the
SDP offer which excludes this closed data channel SHOULD be client SHOULD generate an SDP offer which excludes this closed data
generated. channel.
The application must also close any data channel that was externally The application MUST also close any data channel that was externally
negotiated, for which the stream identifiers are not listed in an negotiated, for which the stream identifiers are not listed in an
incoming SDP offer. incoming SDP offer.
A closed data channel using local close (SCTP reset), without an A closed data channel using local close (SCTP reset), without an
additional SDP offer/answer to close it, may be reused for a new data additional SDP offer/answer to close it, may be reused for a new data
channel. This can only be done via new SDP offer/answer, describing channel. This can only be done via new SDP offer/answer, describing
the new sub-protocol and its attributes, only after the corresponding the new sub-protocol and its attributes, only after the corresponding
data channel close acknowledgement is received from the peer (i.e. data channel close acknowledgement is received from the peer (i.e.
SCTP reset of both incoming and outgoing streams is completed). This SCTP reset of both incoming and outgoing streams is completed). This
restriction is to avoid the race conditions between arrival of "SDP restriction is to avoid the race conditions between arrival of "SDP
offer which reuses stream" with "SCTP reset which closes outgoing offer which reuses stream" with "SCTP reset which closes outgoing
stream" at the peer stream" at the peer
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 6.2.5. Various SDP Offer/Answer Scenarios and Considerations
SDP offer has no a=dcmap attributes SDP offer has no a=dcmap attributes
* Initial SDP offer: No data channel negotiated yet. * Initial SDP offer: No data channel is negotiated yet. The DTLS
connection and SCTP association is negotiated and, if agreed,
established as per [I-D.ietf-mmusic-sctp-sdp].
* Subsequent SDP offer: All the externally negotiated data * Subsequent SDP offer: All the externally negotiated data
channels must be closed now. The DTLS/SCTP association remains channels are expected be closed now. The DTLS/SCTP association
open for external or internal negotiation of data channels. remains open for external or internal negotiation of data
channels.
SDP answer has no a=dcmap attributes SDP answer has no a=dcmap attributes
* Initial SDP answer: Either the peer does not support dcmap * Initial SDP answer: Either the peer does not support dcmap
attributes or it rejected all the data channels. In either attributes or it rejected all the data channels. In either
case offerer closes all the externally negotiated data channels case offerer closes all the externally negotiated data channels
that were open at the time of initial offer. The DTLS/SCTP that were open at the time of initial offer. The DTLS/SCTP
association will still be setup. association will still be setup.
* Sub-sequent SDP answer: All the externally negotiated data * Subsequent SDP answer: All the externally negotiated data
channels must be closed now. The DTLS/SCTP association remains channels are expected be closed now. The DTLS/SCTP association
open for future external or internal negotiation of data remains open for future external or internal negotiation of
channels. data channels.
SDP offer has no a=dcsa attributes for a data channel. SDP offer has no a=dcsa attributes for a data channel.
* This is allowed and indicates there are no sub-protocol * This is allowed and indicates there are no sub-protocol
parameters to convey. parameters to convey.
SDP answer has no a=dcsa attributes for a data channel. SDP answer has no a=dcsa attributes for a data channel.
* This is allowed and indicates there are no sub-protocol * This is allowed and indicates there are no sub-protocol
parameters to convey in the SDP answer. The number of dcsa parameters to convey in the SDP answer. The number of dcsa
attributes in the SDP answer does not have to match the number attributes in the SDP answer does not have to match the number
of dcsa attributes in the SDP offer. of dcsa attributes in the SDP offer.
6. Examples 7. Examples
SDP offer: SDP offer:
m=application 10001 UDP/DTLS/SCTP webrtc-datachannel m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 10.10.10.1 c=IN IP4 10.10.10.1
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port 5000 a=sctp-port 5000
a=setup:actpass a=setup:actpass
a=connection:new a=connection:new
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
skipping to change at page 20, line 40 skipping to change at page 20, line 40
Figure 3: Example 3 Figure 3: Example 3
The above example is a continuation of the example in Figure 1. The The above example is a continuation of the example in Figure 1. The
SDP offer now removes the MSRP data channel with stream id 2, but SDP offer now removes the MSRP data channel with stream id 2, but
opens a new MSRP data channel with stream id 4. The answerer opens a new MSRP data channel with stream id 4. The answerer
accepted the entire offer. As a result the offerer closes the accepted the entire offer. As a result the offerer closes the
earlier negotiated MSRP related data channel and both offerer and earlier negotiated MSRP related data channel and both offerer and
answerer may start using new the MSRP related data channel. answerer may start using new the MSRP related data channel.
7. Security Considerations 8. Security Considerations
No security considerations are envisaged beyond those already No security considerations are envisaged beyond those already
documented in [RFC4566] documented in [RFC4566]
8. IANA Considerations 9. IANA Considerations
To be completed. As [I-D.ietf-rtcweb-data-protocol] this document 9.1. Subprotocol identifiers
should refer to IANA's WebSocket Subprotocol Name Registry defined in
[RFC6455].
9. Acknowledgments Registration of new subprotocol identifiers is performed using the
existing IANA table "WebSocket Subprotocol Name Registry".
The following text should be added following the title of the table.
"This table also includes subprotocol identifiers specified for usage
within a WebRTC data channel."
The following reference should be added to under the heading
reference: "RFC XXXX".
This document assigns no new values to this table.
NOTE to RFC Editor: Please replace "XXXX" with the number of this
RFC.
10. Acknowledgments
The authors wish to acknowledge the borrowing of ideas from other The authors wish to acknowledge the borrowing of ideas from other
internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley
and Gavin Llewellyn, and to thank Christian Groves, Christer and Gavin Llewellyn, and to thank Christian Groves, Christer
Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe Rauschenbach for Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe Rauschenbach for
their invaluable comments. their invaluable comments.
10. CHANGE LOG 11. CHANGE LOG
10.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00' 11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01'
o New Section 4 regarding applicability to SDP offer/answer only.
o Addition of new Section 9.1 "Subprotocol identifiers" as
subsection of the "IANA Considerations" related Section 9. Also
removal of the temporary note "To be completed. As [I-D.ietf-
rtcweb-data-protocol] this document should refer to IANA's
WebSocket Subprotocol Name Registry defined in [RFC6455]."
o In Section 6.2.2:
* In the first paragraph replacement of the sentence "If an SDP
offer contains both of these parameters then such an SDP offer
will be rejected." with "If an SDP offer contains both of these
parameters then the receiver of such an SDP offer MUST reject
the SDP offer."
* In the second paragraph capitalization of "shall" and "may"
such that both sentences now read: "The SDP answer SHALL echo
the same subprotocol, max-retr, max-time, ordered parameters,
if those were present in the offer, and MAY include a label
parameter. They MAY appear in any order, which could be
different from the SDP offer, in the SDP answer."
* In the third paragraph replacement of the sentence "The same
information MUST be replicated without changes in any
subsequent offer or answer, as long as the data channel is
still opened at the time of offer or answer generation." with
"When sending a subsequent offer or an answer, and for as long
as the data channel is still open, the sender MUST replicate
the same information.".
o In Section 6.2.2 the mapping of data channel types defined in
[I-D.ietf-rtcweb-data-protocol] to the SDP "a=dcmap" attribute
parameters were illustrated using example "a=dcmap" attribute
lines. Replacement of these example "a=dcmap" attribute lines
with just the "a=dcmap" attribute parameters being relevant for
the channel type.
o In Section 6.2.5 the description of bullet point "SDP offer has no
a=dcmap attributes - Initial SDP offer:" was "Initial SDP offer:
No data channel negotiated yet." Replacement of this description
with "Initial SDP offer: No data channel is negotiated yet. The
DTLS connection and SCTP association is negotiated and, if agreed,
established as per [I-D.ietf-mmusic-sctp-sdp]."
o In Section 6.2.5 in both bullet points related to "Subsequent SDP
offer" and "Subsequent SDP answer" replacement of "All the
externally negotiated data channels must be closed now." with "All
the externally negotiated data channels are expected be closed
now.".
o In Section 5.2.2's sixth paragraph beginning with "[ASSUMPTION]"
replacement of the two occurrences of "must" with "MUST".
o In Section 6.1.1.1 in the definition of the ABNF rule "dcmap-opt"
there was a comment saying that "Either only maxretr-opt or
maxtime-opt is present. Both MUST not be present." Removal of
the second normative sentence and instead addition of following
new paragraph to the end of this section: "Within an 'a=dcmap'
attribute line's 'dcmap-opt' value either only one 'maxretr-opt'
parameter or one 'maxtime-opt' parameter is present. Both MUST
NOT be present."
o In Section 6.1.1.7 replacement of the first sentence "The
'ordered' parameter with value "true" indicates that DATA chunks
in the channel MUST be dispatched to the upper layer by the
receiver while preserving the order." with "The 'ordered'
parameter with value "true" indicates that the receiver MUST
dispatch DATA chunks in the data channel to the upper layer while
preserving the order.".
o In Section 6.2.3's first paragraph replacement of the one
occurrence of "must" with "..., it MUST wait until ...".
o In Section 6.2.4:
* In the second paragraph replacement of "must" with "... whether
this closing MUST in addition ..."
* In the third paragraph replacement of the sentence "The port
value for the "m" line SHOULD not be changed (e.g., to zero)
when closing a data channel ..." with "The offerer SHOULD NOT
change the port value for the "m" line (e.g., to zero) when
closing a data channel ...".
* In the last but two paragraph replacement of the sentence "...
then an SDP offer which excludes this closed data channel
SHOULD be generated." with "... then the client SHOULD generate
an SDP offer which excludes this closed data channel.".
* In the last but one paragraph replacement of "must" with "The
application MUST also close...".
o In Section 6.1.2 addition of following note after the formal
definition of the 'a=dcsa' attribute: "Note that the above
reference to RFC 4566 defines were the attribute definition can be
found; it does not provide any limitation on support of attributes
defined in other documents in accordance with this attribute
definition."
11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00'
o In Section 3 "WebRTC data channel" was defined as "A bidirectional o In Section 3 "WebRTC data channel" was defined as "A bidirectional
channel consisting of paired SCTP outbound and inbound streams." channel consisting of paired SCTP outbound and inbound streams."
Replacement of this definition with "Data channel: A WebRTC data Replacement of this definition with "Data channel: A WebRTC data
channel as specified in [I-D.ietf-rtcweb-data-channel]", and channel as specified in [I-D.ietf-rtcweb-data-channel]", and
consistent usage of "data channel" in the remainder of the consistent usage of "data channel" in the remainder of the
document including the document's headline." document including the document's headline."
o In Section 4 removal of following note: 'OPEN ISSUE: The syntax in o In Section 5 removal of following note: 'OPEN ISSUE: The syntax in
[I-D.ietf-mmusic-sctp-sdp] may change as that document progresses. [I-D.ietf-mmusic-sctp-sdp] may change as that document progresses.
In particular we expect "webrtc-datachannel" to become a more In particular we expect "webrtc-datachannel" to become a more
general term.' general term.'
o Consistent usage of '"m" line' in whole document as per [RFC4566]. o Consistent usage of '"m" line' in whole document as per [RFC4566].
o In Section 5.1.1 removal of the example dcmap attribute line o In Section 6.1.1 removal of the example dcmap attribute line
'a=dcmap:2 subprotocol="BFCP";label="channel 2' as there are 'a=dcmap:2 subprotocol="BFCP";label="channel 2' as there are
already four examples right after the ABNF rules in already four examples right after the ABNF rules in
Section 5.1.1.1. Corresponding removal of following related note: Section 6.1.1.1. Corresponding removal of following related note:
"Note: This document does not provide a complete specification of "Note: This document does not provide a complete specification of
how to negotiate the use of a WebRTC data channel to transport how to negotiate the use of a WebRTC data channel to transport
BFCP. Procedures specific to each sub-protocol such as BFCP will BFCP. Procedures specific to each sub-protocol such as BFCP will
be documented elsewhere. The use of BFCP is only an example of be documented elsewhere. The use of BFCP is only an example of
how the generic procedures described herein might apply to a how the generic procedures described herein might apply to a
specific sub-protocol." specific sub-protocol."
o In Section 5.1.1 removal of following note: "Note: This attribute o In Section 6.1.1 removal of following note: "Note: This attribute
is derived from attribute "webrtc-DataChannel", which was defined is derived from attribute "webrtc-DataChannel", which was defined
in old version 03 of the following draft, but which was removed in old version 03 of the following draft, but which was removed
along with any support for SDP external negotiation in subsequent along with any support for SDP external negotiation in subsequent
versions: [I-D.ietf-mmusic-sctp-sdp]." versions: [I-D.ietf-mmusic-sctp-sdp]."
o Insertion of following new sentence to the beginning of o Insertion of following new sentence to the beginning of
Section 5.1.1.1: "dcmap is a media level attribute having Section 6.1.1.1: "dcmap is a media level attribute having
following ABNF syntax:" following ABNF syntax:"
o Insertion of new Section 5.1.1.2 containing the dcmap-stream-id o Insertion of new Section 6.1.1.2 containing the dcmap-stream-id
specifying sentence, which previously was placed right before the specifying sentence, which previously was placed right before the
formal ABNF rules. Removal of the sentence 'Stream is a mandatory formal ABNF rules. Removal of the sentence 'Stream is a mandatory
parameter and is noted directly after the "a=dcmap:" attribute's parameter and is noted directly after the "a=dcmap:" attribute's
colon' as this information is part of the ABNF specification. colon' as this information is part of the ABNF specification.
o In Section 5.1.1.1 modification of the 'ordering-value' values o In Section 6.1.1.1 modification of the 'ordering-value' values
from "0" or "1" to "true" or "false". Corresponding text from "0" or "1" to "true" or "false". Corresponding text
modifications in Section 5.1.1.7. modifications in Section 6.1.1.7.
o In Section 5.1.1.1 the ABNF definition of "quoted-string" referred o In Section 6.1.1.1 the ABNF definition of "quoted-string" referred
to rule name "escaped-char", which was not defined. Instead a to rule name "escaped-char", which was not defined. Instead a
rule with name "escaped" was defined. Renamed that rule's name to rule with name "escaped" was defined. Renamed that rule's name to
"escaped-char". "escaped-char".
o Insertion of a dedicated note right after the "a=dcmap:4" o Insertion of a dedicated note right after the "a=dcmap:4"
attribute example in Section 5.1.1.1 regarding the non-printable attribute example in Section 6.1.1.1 regarding the non-printable
"escaped-char" character within the "label" value. "escaped-char" character within the "label" value.
o In Section 5.1.2's second paragraph replacement of "sctp stream o In Section 6.1.2's second paragraph replacement of "sctp stream
identifier" with "SCTP stream identifier". identifier" with "SCTP stream identifier".
o In first paragraph of Section 5.2.1 replacement of first two o In first paragraph of Section 6.2.1 replacement of first two
sentences 'For the SDP-based external negotiation described in sentences 'For the SDP-based external negotiation described in
this document, the initial offerer based "SCTP over DTLS" owns by this document, the initial offerer based "SCTP over DTLS" owns by
convention the even stream identifiers whereas the initial convention the even stream identifiers whereas the initial
answerer owns the odd stream identifiers. This ownership is answerer owns the odd stream identifiers. This ownership is
invariant for the whole lifetime of the signaling session, e.g. it invariant for the whole lifetime of the signaling session, e.g. it
does not change if the initial answerer sends a new offer to the does not change if the initial answerer sends a new offer to the
initial offerer.' with 'If an SDP offer / answer exchange (could initial offerer.' with 'If an SDP offer / answer exchange (could
be the initial or a subsequent one) results in a UDP/DTLS/SCTP or be the initial or a subsequent one) results in a UDP/DTLS/SCTP or
TCP/DTLS/SCTP based media description being accepted, and if this TCP/DTLS/SCTP based media description being accepted, and if this
SDP offer / answer exchange results in the establishment of a new SDP offer / answer exchange results in the establishment of a new
SCTP association, then the SDP offerer owns the even SCTP stream SCTP association, then the SDP offerer owns the even SCTP stream
ids of this new SCTP association and the answerer owns the odd ids of this new SCTP association and the answerer owns the odd
SCTP stream identifiers. If this "m" line is removed from the SCTP stream identifiers. If this "m" line is removed from the
signaling session (its port number set to zero), and if usage of signaling session (its port number set to zero), and if usage of
this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is
renegotiated later on, then the even and odd SCTP stream renegotiated later on, then the even and odd SCTP stream
identifier ownership is redetermined as well as described above.' identifier ownership is redetermined as well as described above.'
o In Section 5.2.3 the first action of an SDP answerer, when o In Section 6.2.3 the first action of an SDP answerer, when
receiving an SDP offer, was described as "Applies the SDP offer. receiving an SDP offer, was described as "Applies the SDP offer.
Note that the browser ignores data channel specific attributes in Note that the browser ignores data channel specific attributes in
the SDP." Replacement of these two sentences with "Parses and the SDP." Replacement of these two sentences with "Parses and
applies the SDP offer. Note that the typical parser normally applies the SDP offer. Note that the typical parser normally
ignores unknown SDP attributes, which includes data channel ignores unknown SDP attributes, which includes data channel
related attributes." related attributes."
o In Section 5.2.3 the second sentence of the third SDP answerer o In Section 6.2.3 the second sentence of the third SDP answerer
action was "Note that the browser is asked to create data channels action was "Note that the browser is asked to create data channels
with stream identifiers not "owned" by the agent.". Replacement with stream identifiers not "owned" by the agent.". Replacement
of this sentence with "Note that the agent is asked to create data of this sentence with "Note that the agent is asked to create data
channels with SCTP stream identifiers contained in the SDP offer channels with SCTP stream identifiers contained in the SDP offer
if the SDP offer is accepted." if the SDP offer is accepted."
o In Section 5.2.4 the third paragraph began with "A data channel o In Section 6.2.4 the third paragraph began with "A data channel
can be closed by sending a new SDP offer which excludes the dcmap can be closed by sending a new SDP offer which excludes the dcmap
and dcsa attribute lines for the data channel. The port value for and dcsa attribute lines for the data channel. The port value for
the m line should not be changed (e.g., to zero) when closing a the m line should not be changed (e.g., to zero) when closing a
data channel (unless all data channels are being closed and the data channel (unless all data channels are being closed and the
SCTP association is no longer needed), since this would close the SCTP association is no longer needed), since this would close the
SCTP association and impact all of the data channels. If the SCTP association and impact all of the data channels. If the
answerer accepts the SDP offer then it MUST also exclude the answerer accepts the SDP offer then it MUST also exclude the
corresponding attribute lines in the answer. ..." Replacement of corresponding attribute lines in the answer. ..." Replacement of
this part with "The intention to close a data channel can be this part with "The intention to close a data channel can be
signaled by sending a new SDP offer which excludes the "a=dcmap:" signaled by sending a new SDP offer which excludes the "a=dcmap:"
skipping to change at page 23, line 34 skipping to change at page 25, line 49
value for the "m" line SHOULD not be changed (e.g., to zero) when value for the "m" line SHOULD not be changed (e.g., to zero) when
closing a data channel (unless all data channels are being closed closing a data channel (unless all data channels are being closed
and the SCTP association is no longer needed), since this would and the SCTP association is no longer needed), since this would
close the SCTP association and impact all of the data channels. close the SCTP association and impact all of the data channels.
If the answerer accepts the SDP offer then it MUST close those If the answerer accepts the SDP offer then it MUST close those
data channels whose "a=dcmap:" and "a=dcsa:" attribute lines were data channels whose "a=dcmap:" and "a=dcsa:" attribute lines were
excluded from the received SDP offer, unless those data channels excluded from the received SDP offer, unless those data channels
were already closed, and it MUST also exclude the corresponding were already closed, and it MUST also exclude the corresponding
attribute lines in the answer." attribute lines in the answer."
o In Section 5.2.4 the hanging text after the third paragraph was o In Section 6.2.4 the hanging text after the third paragraph was
"This delayed close is to handle cases where a successful SDP "This delayed close is to handle cases where a successful SDP
answer is not received, in which case the state of session should answer is not received, in which case the state of session should
be kept per the last successful SDP offer/answer." Replacement of be kept per the last successful SDP offer/answer." Replacement of
this sentence with "This delayed closure is RECOMMENDED in order this sentence with "This delayed closure is RECOMMENDED in order
to handle cases where a successful SDP answer is not received, in to handle cases where a successful SDP answer is not received, in
which case the state of the session SHOULD be kept per the last which case the state of the session SHOULD be kept per the last
successful SDP offer/answer." successful SDP offer/answer."
o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects
Section 5.1.1 contained already procedural descriptions related to Section 6.1.1 contained already procedural descriptions related to
data channel reliability negotiation. Creation of new data channel reliability negotiation. Creation of new
Section 5.2.2 and moval of reliability negotiation related text to Section 6.2.2 and moval of reliability negotiation related text to
this new section. this new section.
10.2. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02' 11.3. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02'
o Removal of note "[ACTION ITEM]" from section "subprotocol o Removal of note "[ACTION ITEM]" from section "subprotocol
parameter". As [I-D.ietf-rtcweb-data-protocol] this document parameter". As [I-D.ietf-rtcweb-data-protocol] this document
should refer to IANA's WebSocket Subprotocol Name Registry defined should refer to IANA's WebSocket Subprotocol Name Registry defined
in [RFC6455]. in [RFC6455].
o In whole document, replacement of "unreliable" with "partially o In whole document, replacement of "unreliable" with "partially
reliable", which is used in [I-D.ietf-rtcweb-data-channel] and in reliable", which is used in [I-D.ietf-rtcweb-data-channel] and in
[I-D.ietf-rtcweb-data-protocol] in most places. [I-D.ietf-rtcweb-data-protocol] in most places.
skipping to change at page 25, line 7 skipping to change at page 27, line 19
o In the "Examples" section, in the first two SDP offer examples in o In the "Examples" section, in the first two SDP offer examples in
the a=dcmap attribute lines 'label="BGCP"' was replaced with the a=dcmap attribute lines 'label="BGCP"' was replaced with
'label="BFCP"'. 'label="BFCP"'.
o In all examples, the "m" line proto value "DTLS/SCTP" was replaced o In all examples, the "m" line proto value "DTLS/SCTP" was replaced
with "UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were with "UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were
replaced with "a=max-message-size" attribute lines, as per draft- replaced with "a=max-message-size" attribute lines, as per draft-
ietf-mmusic-sctp-sdp-12. ietf-mmusic-sctp-sdp-12.
10.3. Changes against '-01' 11.4. Changes against '-01'
o Formal syntax for dcmap and dcsa attribute lines. o Formal syntax for dcmap and dcsa attribute lines.
o Making subprotocol as an optional parameter in dcmap. o Making subprotocol as an optional parameter in dcmap.
o Specifying disallowed parameter combinations for max-time and max- o Specifying disallowed parameter combinations for max-time and max-
retr. retr.
o Clarifications on WebRTC data channel close procedures. o Clarifications on WebRTC data channel close procedures.
10.4. Changes against '-00' 11.5. Changes against '-00'
o Revisions to identify difference between internal and external o Revisions to identify difference between internal and external
negotiation and their usage. negotiation and their usage.
o Introduction of more generic terminology, e.g. "application" o Introduction of more generic terminology, e.g. "application"
instead of "browser". instead of "browser".
o Clarification of how "max-retr and max-time affect the usage of o Clarification of how "max-retr and max-time affect the usage of
unreliable and reliable WebRTC data channels. unreliable and reliable WebRTC data channels.
o Updates of examples to take into account the SDP syntax changes o Updates of examples to take into account the SDP syntax changes
introduced with draft-ietf-mmusic-sctp-sdp-07. introduced with draft-ietf-mmusic-sctp-sdp-07.
o Removal of the SCTP port number from the a=dcmap and a=dcsa o Removal of the SCTP port number from the a=dcmap and a=dcsa
attributes as this is now contained in the a=sctp-port attribute, attributes as this is now contained in the a=sctp-port attribute,
and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP
association on top of the DTLS connection. association on top of the DTLS connection.
11. References 12. References
11.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June with Session Description Protocol (SDP)", RFC 3264, June
2002. 2002.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[I-D.ietf-rtcweb-jsep] [I-D.ietf-rtcweb-jsep]
Uberti, J., Jennings, C., and E. Rescorla, "Javascript Uberti, J., Jennings, C., and E. Rescorla, "Javascript
Session Establishment Protocol", draft-ietf-rtcweb-jsep-08 Session Establishment Protocol", draft-ietf-rtcweb-jsep-09
(work in progress), October 2014. (work in progress), March 2015.
[I-D.ietf-rtcweb-data-channel] [I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-13 (work in Channels", draft-ietf-rtcweb-data-channel-13 (work in
progress), January 2015. progress), January 2015.
[I-D.ietf-mmusic-sctp-sdp] [I-D.ietf-mmusic-sctp-sdp]
Holmberg, C., Loreto, S., and G. Camarillo, "Stream Holmberg, C., Loreto, S., and G. Camarillo, "Stream
Control Transmission Protocol (SCTP)-Based Media Transport Control Transmission Protocol (SCTP)-Based Media Transport
in the Session Description Protocol (SDP)", draft-ietf- in the Session Description Protocol (SDP)", draft-ietf-
mmusic-sctp-sdp-14 (work in progress), March 2015. mmusic-sctp-sdp-14 (work in progress), March 2015.
[WebRtcAPI] [WebRtcAPI]
Bergkvist, A., Burnett, D., Jennings, C., and A. Bergkvist, A., Burnett, D., Jennings, C., and A.
Narayanan, "WebRTC 1.0: Real-time Communication Between Narayanan, "WebRTC 1.0: Real-time Communication Between
Browsers", World Wide Web Consortium WD-webrtc-20130910, Browsers", World Wide Web Consortium WD-webrtc-20130910,
September 2013, September 2013,
<http://www.w3.org/TR/2013/WD-webrtc-20130910/>. <http://www.w3.org/TR/2013/WD-webrtc-20130910/>.
11.2. Informative References 12.2. Informative References
[I-D.ietf-rtcweb-data-protocol] [I-D.ietf-rtcweb-data-protocol]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel
Establishment Protocol", draft-ietf-rtcweb-data- Establishment Protocol", draft-ietf-rtcweb-data-
protocol-09 (work in progress), January 2015. protocol-09 (work in progress), January 2015.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007. 4960, September 2007.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
 End of changes. 92 change blocks. 
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