draft-ietf-mmusic-data-channel-sdpneg-02.txt   draft-ietf-mmusic-data-channel-sdpneg-03.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: October 12, 2015 Alcatel-Lucent Expires: January 22, 2016 Alcatel-Lucent
R. Ejzak R. Ejzak
J. Marcon J. Marcon
Unaffiliated Unaffiliated
April 10, 2015 July 21, 2015
SDP-based Data Channel Negotiation SDP-based Data Channel Negotiation
draft-ietf-mmusic-data-channel-sdpneg-02 draft-ietf-mmusic-data-channel-sdpneg-03
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
can be done using either the internal in-band band (also referred to can be done using either the in-band Data Channel Establishment
as 'internal' for the rest of the document) Data Channel Protocol (DCEP) or using some out-of-band non-DCEP protocol. This
Establishment Protocol or some external out-of-band simply referred
to as 'external negotiation' in the rest of the document . This
document specifies how the SDP offer/answer exchange can be used to document specifies how the SDP offer/answer exchange can be used to
achieve such an external negotiation. Even though data channels are achieve such an out-of-band non-DCEP negotiation. Even though data
designed for RTCWeb use initially they may be used by other protocols channels are designed for RTCWeb use initially they may be used by
like, but not limited to, the CLUE protocol. This document is other protocols like, but not limited to, the CLUE protocol. This
intended to be used wherever data channels are used. document is intended to be used wherever data channels are used.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 12, 2015. This Internet-Draft will expire on January 22, 2016.
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
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
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 . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
5. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5 5.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5
5.2. Generic External Negotiation . . . . . . . . . . . . . . 6 5.2. Generic Non-DCEP Negotiation . . . . . . . . . . . . . . 6
5.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6 5.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6
5.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6 5.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6
5.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 7 5.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 8
6. SDP-based External Negotiation . . . . . . . . . . . . . . . 8 6. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 8
6.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 8 6.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 9
6.1.1. SDP Attribute for Data Channel Parameter Negotiation 8 6.1.1. SDP Attribute for Data Channel Parameter Negotiation 9
6.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 8 6.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 9
6.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 10 6.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 11
6.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 10 6.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 11
6.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 10 6.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 11
6.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 10 6.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 11
6.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 11 6.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 12
6.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 11 6.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 12
6.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 11 6.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 12
6.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12 6.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 14
6.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 13 6.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 14
6.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13 6.2.2. Negotiating Data Channel Parameters . . . . . . . . . 14
6.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14 6.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 15
6.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16 6.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 17
6.2.5. Various SDP Offer/Answer Scenarios and Considerations 17 6.2.5. Various SDP Offer/Answer Scenarios and Considerations 18
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
9.1. Subprotocol identifiers . . . . . . . . . . . . . . . . . 20 9.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 21
9.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 9.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 22
11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 22
11.1. Changes against 'draft-ietf-mmusic-data-channel- 11.1. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 21 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 22
11.2. Changes against 'draft-ietf-mmusic-data-channel- 11.2. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 23 sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 23
11.3. Changes against 'draft-ejzak-mmusic-data-channel- 11.3. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 26 sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 25
11.4. Changes against '-01' . . . . . . . . . . . . . . . . . 27 11.4. Changes against 'draft-ejzak-mmusic-data-channel-
11.5. Changes against '-00' . . . . . . . . . . . . . . . . . 27 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 11.5. Changes against '-01' . . . . . . . . . . . . . . . . . 29
12.1. Normative References . . . . . . . . . . . . . . . . . . 28 11.6. Changes against '-00' . . . . . . . . . . . . . . . . . 29
12.2. Informative References . . . . . . . . . . . . . . . . . 28 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 12.1. Normative References . . . . . . . . . . . . . . . . . . 30
12.2. Informative References . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
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 DCEP or out-
band protocol for creating them. Each data channel consists of of-band non-DCEP protocols for creating them. Each data channel
paired SCTP streams sharing the same SCTP Stream Identifier. Data consists of paired SCTP streams sharing the same SCTP Stream
channels are created by endpoint applications through the WebRTC API, Identifier. Data channels are created by endpoint applications
or other users of data channel like CLUE, and can be used to through the WebRTC API, or other users of data channel like CLUE, and
transport proprietary or well-defined protocols, which in the latter can be used to transport proprietary or well-defined protocols, which
case can be signaled by the data channel "sub-protocol" parameter, in the latter case can be signaled by the data channel "sub-protocol"
conceptually similar to the WebSocket "sub-protocol". However, apart parameter, conceptually similar to the WebSocket "sub-protocol".
from the "sub-protocol" value transmitted to the peer, RTCWeb leaves However, apart from the "sub-protocol" value transmitted to the peer,
it open how endpoint applications can agree on how to instantiate a RTCWeb leaves it open how endpoint applications can agree on how to
given sub-protocol on a data channel, and whether it is signaled in- instantiate a given sub-protocol on a data channel, and whether it is
band or out-of-band (or both). In particular, the SDP offer signaled in-band using DCEP or out-of-band using a non-DCEP protocol
generated by the application includes no channel-specific (or both). In particular, the SDP offer generated by the application
information. includes no channel-specific information.
This document defines SDP-based out-of-band negotiation procedures to This document defines SDP offer/answer negotiation procedures to
establish data channels for transport of well-defined sub-protocols. establish data channels for transport of well-defined sub-protocols,
to enable out-of-band negotiation.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Terminology 3. Terminology
This document uses the following terms: This document uses the following terms:
Data channel: A WebRTC data channel as specified in Data channel: A WebRTC data channel as specified in
[I-D.ietf-rtcweb-data-channel]. [I-D.ietf-rtcweb-data-channel].
Data channel stack: An entity which, upon application request, Data channel stack: An entity which, upon application request,
runs data channel protocol to keep track of states, sending and runs the data channel protocol to keep track of states, sending
receive data. If the application is browser based JavaScript and receive data. If the application is a browser based
application then this stack resides in the browser. If the JavaScript application then this stack resides in the browser. If
application is a native application then this stack resides in the application is a native application then this stack resides in
application and accessible to it via some sort of APIs. the application and is accessible via some sort of APIs.
Data channel properties: fixed properties assigned to a data Data channel properties: Fixed properties assigned to a data
channel at the time of its creation. Some of these properties channel at the time of its creation. Some of these properties
determine the way the data channel stack transmits data on this determine the way the data channel stack transmits data on this
channel (e.g., stream identifier, reliability, order of channel (e.g., stream identifier, reliability, order of
delivery...). delivery...).
DCEP - Data Channel Establishment Protocol defined in DCEP: Data Channel Establishment Protocol defined in
[I-D.ietf-rtcweb-data-protocol].
External negotiation: Data channel negotiation based on SDP offer/
answer outlined in this specification.
Internal negotiation: Data channel negotiation based on the Data
Channel Establishment Protocol defined in
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
In-band: transmission through the peer-to-peer SCTP association. In-band: Transmission through the peer-to-peer SCTP association.
In-band negotiation: data channel negotiation based on the Data
Channel Establishment Protocol defined in
[I-D.ietf-rtcweb-data-protocol].
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 SCTP Stream Sequence Number (SSN): the SCTP stream sequence number
as specified in [RFC4960].
Stream identifier: The identifier of the outbound and inbound SCTP
streams composing a data channel. streams composing a data channel.
4. Applicability Statement 4. Applicability Statement
The mechanism in this specification only applies to the Session The mechanism in this specification only applies to the Session
Description Protocol (SDP) [RFC4566], when used together with the SDP Description Protocol (SDP) [RFC4566], when used together with the SDP
offer/answer mechanism [RFC3264]. 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. Data Channels 5. Data Channels
This section summarizes how data channels work in general. Note that This section summarizes how data channels work in general.
the references to 'browser' here is intentional as in this specific
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 by providing a number of
by providing a number of setup parameters (sub-protocol, label, setup parameters (sub-protocol, label, reliability, order of
reliability, order of delivery, priority). The application also delivery, priority). The application also specifies if it wants to
specifies if it wants to make use of the in-band negotiation using make use of the negotiation using the DCEP
the DCEP [I-D.ietf-rtcweb-data-protocol], or if the application [I-D.ietf-rtcweb-data-protocol], or if the application intends to
intends to perform an "external negotiation" using some other in-band negotiate data channels using the SDP offer/answer protocol.
or out-of-band mechanism.
In any case, the SDP offer generated by the browser is per In any case, the SDP offer generated by the browser is per
[I-D.ietf-mmusic-sctp-sdp]. In brief, it contains one "m" line for [I-D.ietf-mmusic-sctp-sdp]. In brief, it contains one "m" line for
the SCTP association on top of which data channels will run, and one the SCTP association on top of which data channels will run:
attribute per protocol assigned to the SCTP ports:
m=application 54111 UDP/DTLS/SCTP webrtc-datachannel m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 79.97.215.79 c=IN IP4 79.97.215.79
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
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.
5.1. Stream Identifier Numbering 5.1. Stream Identifier Numbering
[Editor's note: This entire Section 5.1 could possibly be removed as
there is another section (Section 6.2.1) which is dedicated to SCTP
stream id usage.]
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.
Which set of stream identifiers is owned by which endpoint is Which set of stream identifiers is owned by which endpoint is
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 with the DCEP, 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 negotiated via some non-DCEP protocol, no
by default. convention is defined by default.
5.2. Generic External Negotiation 5.2. Generic Non-DCEP Negotiation
[Editor's note: As this document now focuses on SDP offer/answer
negotiation only, should this entire Section 5.2 (and all its sub-
sections) be removed? Parts of the information provided in these
sub-sections might be moved to Section 6, Section 6.2.1 and
Section 6.2.3 as indicated below in further editor notes. Another
option might be to move this section and its sub-section to an
informative appendix.]
5.2.1. Overview 5.2.1. Overview
In-band negotiation only provides for negotiation of data channel DCEP 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. Non-DCEP negotiation can be defined to
allow negotiation of parameters beyond those handled by in-band allow negotiation of parameters beyond those handled by DCEP
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 6.1.2 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 [Editor's note: The information in the preceding paragraph might be
moved to Section 6.]
The following procedures are common to all methods of non-DCEP
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 offer/
some other protocol associated with the signaling channel). answer or some other protocol associated with the signaling channel).
[Editor's note: The preceding paragraph could be deleted.]
5.2.2. 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 non-DCEP 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 DCEP 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.
[Editor's note: The information in the preceding paragraph could be
moved to Section 6.2.1.]
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 non-DCEP negotiation, the data channel stack creates
the data channel locally without sending any DATA_CHANNEL_OPEN the data channel locally without sending any DATA_CHANNEL_OPEN
message in-band, and sets the data channel state to Connecting if the message in-band [Editor's note: The information in this first part of
SCTP association is not yet established, or sets the data channel the sentence could be moved to section 6.2.3], and sets the data
state to Open if the SCTP association is already established. The channel state to Connecting if the SCTP association is not yet
side which starts external negotiation creates data channel using established, or sets the data channel state to Open if the SCTP
underlying data channel stack API and the data channel is put into association is already established. The side which starts non-DCEP
open state immediately (assuming ICE, SCTP procedures were already negotiation creates a data channel using underlying data channel
done). However, the application can't send data on this data channel stack API and the data channel is put into open state immediately
until external negotiation is complete with the peer. This is (assuming ICE, SCTP procedures were already done). [Editor's note:
because peer needs to be aware and accept the data channel via The API related information could be deleted.] However, the
external negotiation. The peer after accepting the data channel application can't send data on this data channel until non-DCEP
offer can start sending data immediately. This implies that the negotiation is complete with the peer. This is because the peer
offerer may get data channel message before external negotiation is needs to be aware and accept the data channel via non-DCEP
complete and the application should be ready to handle it. negotiation. The peer after accepting the data channel offer can
start sending data immediately. This implies that the offerer may
get data channel sub-protocol messages before non-DCEP negotiation is
complete and the application should be ready to handle it. [Editor's
note: The information in these last four sentences could be moved to
Section 6.2.3.]
If the peer rejects the data channel part of the offer then it If the peer rejects the data channel part of the offer then it
doesn't have to do anything as the data channel was not created using doesn't have to do anything as the data channel was not created using
the stack. The offerer on the other hand needs to close the data the stack. The offerer on the other hand needs to close the data
channel that was opened by invoking relevant data channel stack API channel that was opened by invoking relevant data channel stack API
procedures. procedures.
[Editor's note: The information in the preceding paragraph could be
moved to Section 6.2.3 (to a new bullet point there).]
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 non-DCEP 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 [Editor's note: The preceding paragraph could be deleted.]
properties and sub-protocol properties with the peer's application.
The application then negotiates the data channel properties and sub-
protocol properties with the peer's application using a mechanism
different from DCEP.
[Editor's note: The preceding paragraph could be deleted.]
[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. [Editor's note: The previous
allow data channel creation with any non-conflicting stream sentence could be deleted.] The data channel stack MUST allow data
identifier so that both peers can create the data channel with the channel creation with any non-conflicting stream identifier so that
same stream identifier. both peers can create the data channel with the same stream
identifier. [Editor's note: The information in this sentence could
be moved to Section 6.2.3.]
In case the external negotiation is correlated with an SDP offer/ In case the non-DCEP 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 6.2.3 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.
[Editor's note: The preceding paragraph could be deleted.]
5.2.3. 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 a non-DCEP negotiated
data channel, the data channel stack always performs an in-band SSN data channel, the data channel stack always performs an SCTP SSN
reset for this channel. reset for this channel.
Depending upon the method used for external negotiation and the sub- [Editor's note: The preceding paragraph could be deleted.]
Depending upon the method used for non-DCEP 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 non-DCEP negotiation.
6. SDP-based External Negotiation [Editor's note: The preceding paragraph could be deleted.]
This section defines a method of external negotiation by which two 6. SDP Offer/Answer Negotiation
This section defines a method of non-DCEP 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 the SDP offer/answer model.
6.1. 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 SDP offer/answer
data channels. The first attribute provides for negotiation of negotiation of data channels. The first attribute provides for
channel-specific parameters. The second attribute provides for negotiation of channel-specific parameters. The second attribute
negotiation of sub-protocol-specific parameters. provides for negotiation of sub-protocol-specific parameters.
6.1.1. 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 the DCEP [I-D.ietf-rtcweb-data-protocol]. It is
the data channel properties (reliable/partially reliable, ordered/ assumed that the data channel properties (reliable/partially
unordered) are suitable per the sub-protocol transport requirements. reliable, ordered/unordered) are suitable per the sub-protocol
transport requirements.
6.1.1.1. 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
skipping to change at page 10, line 9 skipping to change at page 11, line 9
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).
Within an 'a=dcmap' attribute line's 'dcmap-opt' value either only Within an 'a=dcmap' attribute line's 'dcmap-opt' value either only
one 'maxretr-opt' parameter or one 'maxtime-opt' parameter is one 'maxretr-opt' parameter or one 'maxtime-opt' parameter MAY be
present. Both MUST NOT be present. present. Both MUST NOT be present.
6.1.1.2. dcmap-stream-id Parameter 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.
6.1.1.3. 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 [WebRtcAPI], an RTCDataChannel object from other
objects. This parameter maps to the 'Label' parameter defined in RTCDataChannel objects. This parameter maps to the 'Label' parameter
[I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is optional. defined in [I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is
If it is not present, then its value defaults to the empty string. optional. 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.
6.1.1.4. 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.
6.1.1.5. 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 maximal number a user message
be retransmitted. The max-retr parameter is optional. If the max- will be retransmitted. The max-retr parameter is optional. If the
retr parameter is not present, then the maximal number of max-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].
6.1.1.6. 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
skipping to change at page 12, line 24 skipping to change at page 13, 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 Note that the above reference to RFC 4566 defines where the attribute
definition can be found; it does not provide any limitation on definition can be found; it does not provide any limitation on
support of attributes defined in other documents in accordance with support of attributes defined in other documents in accordance with
this attribute definition. this attribute definition. Note however that not all SDP attributes
are suitable as "a=dcsa:" parameter. [IANA-SDP-Parameters] contains
the lists of IANA registered session and media level or media level
only SDP attributes.
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
skipping to change at page 13, line 4 skipping to change at page 14, line 6
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.
6.2. Procedures 6.2. Procedures
6.2.1. Managing Stream Identifiers 6.2.1. 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
subsequent one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media
media description being accepted, and if this SDP offer / answer description being accepted, and if this SDP offer/answer exchange
exchange results in the establishment of a new SCTP association, then results in the establishment of a new SCTP association, then the SDP
the SDP offerer owns the even SCTP stream ids of this new SCTP offerer owns the even SCTP stream ids of this new SCTP association
association and the answerer owns the odd SCTP stream identifiers. and the answerer owns the odd SCTP stream identifiers. If this "m"
If this "m" line is removed from the signaling session (its port line is removed from the signaling session (its port number set to
number set to zero), and if usage of this or of a new UDP/DTLS/SCTP zero), and if usage of this or of a new UDP/DTLS/SCTP or TCP/DTLS/
or TCP/DTLS/SCTP based "m" line is renegotiated later on, then the SCTP based "m" line is renegotiated later on, then the even and odd
even and odd SCTP stream identifier ownership is redetermined as well SCTP stream identifier ownership is redetermined as well as described
as described above. above.
This specification allows simultaneous use of external and internal This specification allows simultaneous use of SDP offer/answer and
negotiation. However, a single stream is managed using one method at DCEP negotiation. However, an SDP offer/answer exchange MUST NOT be
a time. Stream ids that are not currently used in SDP can be used initiated if the associated SCTP stream is already negotiated via
for internal negotiation. Stream id allocation per SDP based DCEP. Stream ids that are not currently used in SDP can be used for
external negotiation may not align with DTLS role based allocation. DCEP negotiation. Stream id allocation per SDP offer/answer
This could cause glare conditions when one side trying to do external negotiation may not align with DTLS role based allocation. This
negotiation on a stream id while the other end trying to open a data could cause glare conditions when one side trying to do SDP offer/
channel on the same stream id using internal negotiation. To avoid answer negotiation on a stream id while the other end trying to open
these glare conditions this specification recommends that the data a data channel on the same stream id using DCEP negotiation. To
channel stack user always selects stream ids per above described SDP avoid these glare conditions this specification recommends that the
offer / answer rule even when internal negotiation is used. To avoid data channel stack user always selects stream ids per above described
SDP offer/answer rule even when DCEP 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.
6.2.2. 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 at most
of them can be present in a=dcmap. If an SDP offer contains both of one of them MAY be present in a=dcmap. If an SDP offer contains both
these parameters then the receiver of such an SDP offer MUST reject of these parameters then the receiver of such an SDP offer MUST
the SDP offer. If an SDP answer contains both of these parameters reject the SDP offer. If an SDP answer contains both of these
then the offerer MAY treat it as an error and MAY assume the parameters then the offerer MAY treat it as an error and MAY assume
associated SDP offer/answer failed and MAY take appropriate recovery the associated SDP offer/answer failed and MAY take appropriate
actions. These recovery options are outside the scope of this recovery actions. These recovery options are outside the scope of
specification. 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.
When sending a subsequent offer or an answer, and for as long as the 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 data channel is still open, the sender MUST replicate the same
information. information.
skipping to change at page 14, line 33 skipping to change at page 15, line 38
ordered=false;max-retr=<number of retransmissions> ordered=false;max-retr=<number of retransmissions>
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED
ordered=true;max-time=<lifetime in milliseconds> ordered=true;max-time=<lifetime in milliseconds>
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED
ordered=false;max-time=<lifetime in milliseconds> ordered=false;max-time=<lifetime in milliseconds>
6.2.3. 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 SDP offer/answer
starts with the agent preparing to send an SDP offer. If a peer negotiation starts with the agent preparing to send an SDP offer. If
receives an SDP offer before getting to send a new SDP offer with a peer receives an SDP offer before starting to send a new SDP offer
data channels that are to be externally negotiated, or loses an SDP with data channels that are to be SDP offer/answer negotiated, or
offer glare resolution procedure in this case, it MUST wait until the loses an SDP offer glare resolution procedure in this case, it MUST
ongoing SDP offer/answer completes before resuming the external wait until the ongoing SDP offer/answer completes before resuming the
negotiation procedure. SDP offer/answer 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 offer/answer 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 6.2.1). (see Section 6.2.1).
o As described in Section 5.2.2, if the SCTP association is not yet o Generates a new SDP offer.
established, then the newly created data channels are in the
Connecting state, else if the SCTP association is already
established, then the newly created data channels are in the Open
state.
o Generates a new SDP offer. In the case of browser based
applications the browser generates the offer via the createOffer()
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 SDP offer/answer 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 SDP offer/answer negotiated data channel, as
in Section 6.1 and in Section 6.2.2. described 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 5.2.2, if the SCTP association is not yet
established, then the newly created data channels are in the
Connecting state, else if the SCTP association is already
established, then the newly created data channels are in the Open
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 SDP offer/answer negotiated data
described in Section 6.1 and in Section 6.2.2. channel, as 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 for which the expected dcmap and
state) for which the expected dcmap and dcsa attributes are not dcsa attributes are not present in the SDP answer.
present in the SDP answer.
o Applies the SDP answer. o Applies the SDP answer.
Any data channels in Connecting state are transitioned to the Open
state when the SCTP association is established.
Each agent application MUST wait to send data until it has Each agent application MUST wait to send data until it has
confirmation that the data channel at the peer is in the Open state. confirmation that the data channel at the peer is instantiated. For
For WebRTC, this is when both data channel stacks have channel WebRTC, this is when both data channel stacks have channel parameters
parameters instantiated. This occurs: instantiated. This occurs:
o At both peers when a data channel is created without an o At both peers when a data channel is created without an
established SCTP association, as soon as the data channel stacks established SCTP association, as soon as the SCTP association is
report that the data channel transitions to the Open state from successfully established.
the Connecting state.
o At the agent receiving an SDP offer for which there is an o At the agent receiving an SDP offer for which there is an
established SCTP association, as soon as it creates an externally established SCTP association, as soon as it creates an SDP offer/
negotiated data channel in the Open state based on information answer negotiated data channel based on information signaled in
signaled in the SDP offer. 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 SDP offer/answer
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.
6.2.4. 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- negotiated via SDP offer/answer, the data channel stack always
band SSN reset for this channel. performs an SCTP 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 offerer SHOULD NOT change the port lines for the data channel. The offerer SHOULD NOT change the port
value for the "m" line (e.g. to zero) when closing a data channel value for the "m" line (e.g. to zero) when closing a data channel
(unless all data channels are being closed and the SCTP association (unless all data channels are being closed and the SCTP association
is no longer needed), since this would close the SCTP association and is no longer needed), since this would close the SCTP association and
skipping to change at page 17, line 17 skipping to change at page 17, line 51
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 the SCTP SSN reset or some other reason) without associated SDP offer
client SHOULD generate an SDP offer which excludes this closed data then the client SHOULD generate an SDP offer which excludes this
channel. closed data channel.
The application MUST also close any data channel that was externally The application MUST also close any data channel that was negotiated
negotiated, for which the stream identifiers are not listed in an via SDP offer/answer, for which the stream identifiers are not listed
incoming SDP offer. in an incoming SDP offer.
A closed data channel using local close (SCTP reset), without an A closed data channel using local close (SCTP SSN 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 SSN reset of both incoming and outgoing streams is completed).
restriction is to avoid the race conditions between arrival of "SDP This restriction is to avoid the race conditions between arrival of
offer which reuses stream" with "SCTP reset which closes outgoing "SDP offer which reuses stream" with "SCTP SSN reset which closes
stream" at the peer outgoing stream" at the peer.
6.2.5. 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 is negotiated yet. The DTLS * Initial SDP offer: No data channel is negotiated yet. The DTLS
connection and SCTP association is negotiated and, if agreed, connection and SCTP association is negotiated and, if agreed,
established as per [I-D.ietf-mmusic-sctp-sdp]. established as per [I-D.ietf-mmusic-sctp-sdp].
* Subsequent SDP offer: All the externally negotiated data * Subsequent SDP offer: All the SDP offer/answer negotiated data
channels are expected be closed now. The DTLS/SCTP association channels are expected be closed now. The DTLS/SCTP association
remains open for external or internal negotiation of data remains open for SDP offer/answer or DCEP negotiation of data
channels. 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 the offerer closes all the SDP offer/answer negotiated
that were open at the time of initial offer. The DTLS/SCTP data channels that were open at the time of initial offer. The
association will still be setup. DTLS connection and SCTP association will still be setup.
* Subsequent SDP answer: All the externally negotiated data * Subsequent SDP answer: All the SDP offer/answer negotiated data
channels are expected be closed now. The DTLS/SCTP association channels are expected be closed now. The DTLS/SCTP association
remains open for future external or internal negotiation of remains open for future SDP offer/answer or DCEP negotiation of
data 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
skipping to change at page 19, line 5 skipping to change at page 19, line 40
a=setup:passive a=setup:passive
a=connection:new a=connection:new
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
Figure 1: Example 1 Figure 1: Example 1
In the above example the SDP answerer rejected the data channel with In the above example the SDP answerer rejected the data channel with
stream id 0 either for explicit reasons or because it does not stream id 0 either for explicit reasons or because it does not
understand the a=dcmap attribute. As a result the offerer will close understand the a=dcmap attribute. As a result the offerer will close
the data channel created with the external negotiation option. The the data channel created with the SDP offer/answer negotiation
SCTP association will still be setup over DTLS. At this point the option. The SCTP association will still be setup over DTLS. At this
offerer or the answerer may use internal negotiation to open data point the offerer or the answerer may use DCEP negotiation to open
channels. data channels.
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 19, line 39 skipping to change at page 20, line 34
a=setup:passive a=setup:passive
a=connection:new a=connection:new
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
a=dcmap:2 subprotocol="MSRP";label="MSRP" a=dcmap:2 subprotocol="MSRP";label="MSRP"
a=dcsa:2 accept-types:message/cpim text/plain a=dcsa:2 accept-types:message/cpim text/plain
a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc
Figure 2: Example 2 Figure 2: Example 2
In the above example SDP offer contains data channels for BFCP and In the above example the SDP offer contains data channels for BFCP
MSRP sub-protocols. SDP answer rejected BFCP and accepted MSRP. So, and MSRP sub-protocols. The SDP answer rejected BFCP and accepted
the offerer should close the data channel for BFCP and both offerer MSRP. So, the offerer should close the data channel for BFCP and
and answerer may start using MSRP data channel (after SCTP/DTLS both offerer and answerer may start using the MSRP data channel
association is setup). The data channel with stream id 0 is free and (after SCTP/DTLS association is setup). The data channel with stream
can be used for future internal or external negotiation. id 0 is free and can be used for future DCEP or SDP offer/answer
negotiation.
Continuing on the earlier example in Figure 1. Continuing on the earlier example in Figure 1.
Subsequent SDP offer: Subsequent 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:existing a=connection:existing
skipping to change at page 20, line 35 skipping to change at page 21, line 35
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
a=dcmap:4 subprotocol="MSRP";label="MSRP" a=dcmap:4 subprotocol="MSRP";label="MSRP"
a=dcsa:4 accept-types:message/cpim text/plain a=dcsa:4 accept-types:message/cpim text/plain
a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc
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 accepts
accepted the entire offer. As a result the offerer closes the the entire offer. As a result the offerer closes the earlier
earlier negotiated MSRP related data channel and both offerer and negotiated MSRP related data channel and both offerer and answerer
answerer may start using new the MSRP related data channel. may start using new the MSRP related data channel.
8. 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].
9. IANA Considerations 9. IANA Considerations
9.1. Subprotocol identifiers 9.1. Subprotocol Identifiers
Registration of new subprotocol identifiers is performed using the Registration of new subprotocol identifiers is performed using the
existing IANA table "WebSocket Subprotocol Name Registry". existing IANA table "WebSocket Subprotocol Name Registry".
The following text should be added following the title of the table. The following text should be added following the title of the table.
"This table also includes subprotocol identifiers specified for usage "This table also includes subprotocol identifiers specified for usage
within a WebRTC data channel." within a WebRTC data channel."
The following reference should be added to under the heading The following reference should be added to under the heading
reference: "RFC XXXX". reference: "RFC XXXX".
This document assigns no new values to this table. This document assigns no new values to this table.
NOTE to RFC Editor: Please replace "XXXX" with the number of this NOTE to RFC Editor: Please replace "XXXX" with the number of this
RFC. RFC.
9.2. New SDP Attributes
9.2.1. dcmap
[Editor's note: This section still needs to be completed.]
9.2.2. dcsa
[Editor's note: This section still needs to be completed.]
10. Acknowledgments 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 Roni Even, Christian Groves,
Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe Rauschenbach for Christer Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe
their invaluable comments. Rauschenbach for their invaluable comments.
11. CHANGE LOG 11. CHANGE LOG
11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01' 11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02'
o Move of reference [I-D.ietf-rtcweb-jsep] from the list of
normative references to the list of informative references.
o Addition of [IANA-SDP-Parameters] to the list of informative
references and addition of following two sentences to the first
paragraph after the ABNF definition: "Note however that not all
SDP attributes are suitable as "a=dcsa:" parameter.
[IANA-SDP-Parameters] contains the lists of IANA registered
session and media level or media level only SDP attributes."
o In the introduction replacement of last sentence "This document
defines SDP-based out-of-band negotiation procedures to establish
data channels for transport of well-defined sub-protocols" with
"This document defines SDP offer/answer negotiation procedures to
establish data channels for transport of well-defined sub-
protocols, to enable out-of-band negotiation".
o Throughout the document replacement of "external negotiation" with
"SDP offer/answer negotiation" and removal of term "external
negotiation" from the terminology list in Section 3.
o Throughout the document replacement of "internal negotiation" with
"DCEP" and removal of terms "internal negotiation" and "in-band
negotiation" from the terminology list in Section 3.
o Addition of "SCTP Stream Sequence Number (SSN)" to the list of
terms.
o In Section 6.2.1 replacement of sentence "However, a single stream
is managed using one method at a time." with "However, an SDP
offer/answer exchange MUST NOT be initiated if the associated SCTP
stream is already negotiated via DCEP".
o In Section 6.2.2 replacement of sentence "By definition max-retr
and max-time are mutually exclusive, so only one of them can be
present in a=dcmap" with "By definition max-retr and max-time are
mutually exclusive, so at most one of them MAY be present in
a=dcmap".
o Move of reference [WebRtcAPI] from list of normative references to
list of informative references.
o Removal of almost all text parts, which discussed JavaScript or
other API specific aspects. Such API specific aspects were mainly
discussed in sub-sections of Section 5 and Section 6.
11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01'
o New Section 4 regarding applicability to SDP offer/answer only. o New Section 4 regarding applicability to SDP offer/answer only.
o Addition of new Section 9.1 "Subprotocol identifiers" as o Addition of new Section 9.1 "Subprotocol identifiers" as
subsection of the "IANA Considerations" related Section 9. Also subsection of the "IANA Considerations" related Section 9. Also
removal of the temporary note "To be completed. As [I-D.ietf- removal of the temporary note "To be completed. As [I-D.ietf-
rtcweb-data-protocol] this document should refer to IANA's rtcweb-data-protocol] this document should refer to IANA's
WebSocket Subprotocol Name Registry defined in [RFC6455]." WebSocket Subprotocol Name Registry defined in [RFC6455]."
o In Section 6.2.2: o In Section 6.2.2:
skipping to change at page 23, line 31 skipping to change at page 25, line 44
* In the last but one paragraph replacement of "must" with "The * In the last but one paragraph replacement of "must" with "The
application MUST also close...". application MUST also close...".
o In Section 6.1.2 addition of following note after the formal o In Section 6.1.2 addition of following note after the formal
definition of the 'a=dcsa' attribute: "Note that the above definition of the 'a=dcsa' attribute: "Note that the above
reference to RFC 4566 defines were the attribute definition can be reference to RFC 4566 defines were the attribute definition can be
found; it does not provide any limitation on support of attributes found; it does not provide any limitation on support of attributes
defined in other documents in accordance with this attribute defined in other documents in accordance with this attribute
definition." definition."
11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00' 11.3. 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 5 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.
skipping to change at page 24, line 48 skipping to change at page 27, line 15
o In Section 6.1.2'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 6.2.1 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
be the initial or a subsequent one) results in a UDP/DTLS/SCTP or 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 6.2.3 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.
skipping to change at page 26, line 16 skipping to change at page 28, line 30
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 6.1.1 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 6.2.2 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.
11.3. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02' 11.4. 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 27, line 19 skipping to change at page 29, line 32
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.
11.4. Changes against '-01' 11.5. 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.
11.5. Changes against '-00' 11.6. 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.
skipping to change at page 28, line 10 skipping to change at page 30, line 21
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.
12. References 12. References
12.1. 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,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[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,
2002. DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[I-D.ietf-rtcweb-jsep] [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Uberti, J., Jennings, C., and E. Rescorla, "Javascript Specifications: ABNF", STD 68, RFC 5234,
Session Establishment Protocol", draft-ietf-rtcweb-jsep-09 DOI 10.17487/RFC5234, January 2008,
(work in progress), March 2015. <http://www.rfc-editor.org/info/rfc5234>.
[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]
Bergkvist, A., Burnett, D., Jennings, C., and A.
Narayanan, "WebRTC 1.0: Real-time Communication Between
Browsers", World Wide Web Consortium WD-webrtc-20130910,
September 2013,
<http://www.w3.org/TR/2013/WD-webrtc-20130910/>.
12.2. 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., Ed., "Stream Control Transmission Protocol",
4960, September 2007. RFC 4960, DOI 10.17487/RFC4960, September 2007,
<http://www.rfc-editor.org/info/rfc4960>.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message [RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
Session Relay Protocol (MSRP)", RFC 4975, September 2007. "The Message Session Relay Protocol (MSRP)", RFC 4975,
DOI 10.17487/RFC4975, September 2007,
<http://www.rfc-editor.org/info/rfc4975>.
[RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions [RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
for the Message Sessions Relay Protocol (MSRP)", RFC 4976, for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
September 2007. DOI 10.17487/RFC4976, September 2007,
<http://www.rfc-editor.org/info/rfc4976>.
[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
and P. Kyzivat, "A Session Description Protocol (SDP) and P. Kyzivat, "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer", RFC 5547, Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
May 2009. DOI 10.17487/RFC5547, May 2009,
<http://www.rfc-editor.org/info/rfc5547>.
[RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model [RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model
for the Message Session Relay Protocol (MSRP)", RFC 6135, for the Message Session Relay Protocol (MSRP)", RFC 6135,
February 2011. DOI 10.17487/RFC6135, February 2011,
<http://www.rfc-editor.org/info/rfc6135>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
6455, December 2011. RFC 6455, DOI 10.17487/RFC6455, December 2011,
<http://www.rfc-editor.org/info/rfc6455>.
[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message Establishment for Media Anchoring (CEMA) for the Message
Session Relay Protocol (MSRP)", RFC 6714, August 2012. Session Relay Protocol (MSRP)", RFC 6714,
DOI 10.17487/RFC6714, August 2012,
<http://www.rfc-editor.org/info/rfc6714>.
[I-D.ietf-rtcweb-jsep]
Uberti, J., Jennings, C., and E. Rescorla, "Javascript
Session Establishment Protocol", draft-ietf-rtcweb-jsep-11
(work in progress), July 2015.
[IANA-SDP-Parameters]
"Session Description Protocol (SDP) Parameters", Internet
Assigned Numbers Authority Protocol Assignments Session
Description Protocol (SDP) Parameters,
<http://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xhtml>.
[WebRtcAPI]
Bergkvist, A., Burnett, D., Jennings, C., and A.
Narayanan, "WebRTC 1.0: Real-time Communication Between
Browsers", World Wide Web Consortium WD-webrtc-20150210,
February 2015,
<http://www.w3.org/TR/2015/WD-webrtc-20150210/>.
Authors' Addresses Authors' Addresses
Keith Drage (editor) Keith Drage (editor)
Alcatel-Lucent Alcatel-Lucent
Quadrant, Stonehill Green, Westlea Quadrant, Stonehill Green, Westlea
Swindon Swindon
UK UK
Email: keith.drage@alcatel-lucent.com Email: keith.drage@alcatel-lucent.com
 End of changes. 109 change blocks. 
307 lines changed or deleted 408 lines changed or added

This html diff was produced by rfcdiff 1.42. The latest version is available from http://tools.ietf.org/tools/rfcdiff/