draft-ietf-mmusic-data-channel-sdpneg-06.txt   draft-ietf-mmusic-data-channel-sdpneg-07.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: April 21, 2016 Alcatel-Lucent Expires: June 2, 2016 Alcatel-Lucent
R. Ejzak R. Ejzak
J. Marcon J. Marcon
Unaffiliated Unaffiliated
October 19, 2015 November 30, 2015
SDP-based Data Channel Negotiation SDP-based Data Channel Negotiation
draft-ietf-mmusic-data-channel-sdpneg-06 draft-ietf-mmusic-data-channel-sdpneg-07
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 (Stream Control Transmission Protocol), where each
transport other protocols, called sub-protocols. Data channel setup data channel might be used to transport other protocols, called
can be done using either the in-band Data Channel Establishment subprotocols. Data channel setup can be done using either the in-
Protocol (DCEP) or using some out-of-band non-DCEP protocol. This band Data Channel Establishment Protocol (DCEP) or using some out-of-
document specifies how the SDP offer/answer exchange can be used to band non-DCEP protocol. This document specifies how the SDP (Session
achieve such an out-of-band non-DCEP negotiation. Even though data Description Protocol) offer/answer exchange can be used to achieve
channels are designed for RTCWeb use initially they may be used by such an out-of-band non-DCEP negotiation. Even though data channels
other protocols like, but not limited to, the CLUE protocol. This are designed for RTCWeb use initially, they may be used by other
document is intended to be used wherever data channels are used. protocols like, but not limited to, the CLUE protocol (which is
defined by the IETF "ControLling mUltiple streams for tElepresence"
working group). This 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 June 2, 2016.
This Internet-Draft will expire on April 21, 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
skipping to change at page 2, line 30 skipping to change at page 2, line 31
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 5
5. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 5 5. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 5
5.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 5
5.1.1. SDP Attribute for Data Channel Parameter Negotiation 5 5.1.1. SDP Attribute for Data Channel Parameter Negotiation 5
5.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 6 5.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 6
5.1.1.2. dcmap Multiplexing Category . . . . . . . . . . . 8 5.1.1.2. dcmap Multiplexing Category . . . . . . . . . . . 7
5.1.1.3. dcmap-stream-id Parameter . . . . . . . . . . . . 8 5.1.1.3. dcmap-stream-id Parameter . . . . . . . . . . . . 8
5.1.1.4. label Parameter . . . . . . . . . . . . . . . . . 8 5.1.1.4. label Parameter . . . . . . . . . . . . . . . . . 8
5.1.1.5. subprotocol Parameter . . . . . . . . . . . . . . 9 5.1.1.5. subprotocol Parameter . . . . . . . . . . . . . . 8
5.1.1.6. max-retr Parameter . . . . . . . . . . . . . . . 9 5.1.1.6. max-retr Parameter . . . . . . . . . . . . . . . 8
5.1.1.7. max-time Parameter . . . . . . . . . . . . . . . 9 5.1.1.7. max-time Parameter . . . . . . . . . . . . . . . 9
5.1.1.8. ordered Parameter . . . . . . . . . . . . . . . . 9 5.1.1.8. ordered Parameter . . . . . . . . . . . . . . . . 9
5.1.2. Other Media Level Attributes . . . . . . . . . . . . 10 5.1.1.9. priority Parameter . . . . . . . . . . . . . . . 9
5.1.2. Other Media Level Attributes . . . . . . . . . . . . 9
5.1.2.1. dcsa Attribute . . . . . . . . . . . . . . . . . 10 5.1.2.1. dcsa Attribute . . . . . . . . . . . . . . . . . 10
5.1.2.2. dcsa Multiplexing Category . . . . . . . . . . . 11 5.1.2.2. dcsa Multiplexing Category . . . . . . . . . . . 11
5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 11 5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 11
5.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 11 5.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 11
5.2.2. Negotiating Data Channel Parameters . . . . . . . . . 12 5.2.2. Negotiating Data Channel Parameters . . . . . . . . . 12
5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 13 5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 13
5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 15 5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 15
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 16 5.2.5. Various SDP Offer/Answer Scenarios and Considerations 16
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
skipping to change at page 3, line 4 skipping to change at page 3, line 7
5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 13 5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 13
5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 15 5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 15
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 16 5.2.5. Various SDP Offer/Answer Scenarios and Considerations 16
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
8.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 19 8.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 19
8.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 20 8.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 20
8.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 20 8.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 20
8.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 20 8.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 20
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
10. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21 10. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Changes against 'draft-ietf-mmusic-data-channel- 10.1. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 21 sdpneg-06' . . . . . . . . . . . . . . . . . . . . . . . 21
10.2. Changes against 'draft-ietf-mmusic-data-channel- 10.2. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 22 sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 21
10.3. Changes against 'draft-ietf-mmusic-data-channel- 10.3. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 23 sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 22
10.4. Changes against 'draft-ietf-mmusic-data-channel- 10.4. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 24 sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 23
10.5. Changes against 'draft-ietf-mmusic-data-channel- 10.5. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 25 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 24
10.6. Changes against 'draft-ietf-mmusic-data-channel- 10.6. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 25
10.7. Changes against 'draft-ietf-mmusic-data-channel-
sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 27 sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 27
10.7. Changes against 'draft-ejzak-mmusic-data-channel- 10.8. Changes against 'draft-ejzak-mmusic-data-channel-
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 30 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 30
10.8. Changes against '-01' . . . . . . . . . . . . . . . . . 31 10.9. Changes against '-01' . . . . . . . . . . . . . . . . . 31
10.9. Changes against '-00' . . . . . . . . . . . . . . . . . 31 10.10. Changes against '-00' . . . . . . . . . . . . . . . . . 31
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
11.1. Normative References . . . . . . . . . . . . . . . . . . 32 11.1. Normative References . . . . . . . . . . . . . . . . . . 32
11.2. Informative References . . . . . . . . . . . . . . . . . 32 11.2. Informative References . . . . . . . . . . . . . . . . . 32
Appendix A. Generic Data Channel Negotiation Aspects When Not Appendix A. Generic Data Channel Negotiation Aspects When Not
Using DCEP . . . . . . . . . . . . . . . . . . . . . 34 Using DCEP . . . . . . . . . . . . . . . . . . . . . 33
A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 34 A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 34
A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 35 A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 34
A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 35 A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 34
A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 35 A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 35
A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 36 A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
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 (SCTP over the Datagram
other applications to use data channels and its in-band DCEP or other Transport Layer Security protocol). RTCWeb allows applications to
in-band or out-of-band protocols for creating them. Each data use data channels. RTCWeb defines an in-band DCEP, however other in-
channel consists of paired SCTP streams sharing the same SCTP Stream band or out-of-band protocols may be used for establishing data
Identifier. Data channels are created by endpoint applications channels. Each data channel consists of paired SCTP streams sharing
through the WebRTC API, or other users of data channel like CLUE, and the same SCTP Stream Identifier. Data channels are created by
can be used to transport proprietary or well-defined protocols, which endpoint applications through the WebRTC API (Application Programming
in the latter case can be signaled by the data channel "sub-protocol" Interface), or other users of a data channel like CLUE. They can be
parameter, conceptually similar to the WebSocket "sub-protocol". used to transport proprietary or well-defined protocols, which in the
However, apart from the "sub-protocol" value transmitted to the peer, latter case can be signaled by the data channel "subprotocol"
parameter, conceptually similar to the WebSocket "subprotocol".
However, apart from the "subprotocol" value transmitted to the peer,
RTCWeb leaves it open how endpoint applications can agree on how to RTCWeb leaves it open how endpoint applications can agree on how to
instantiate a given sub-protocol on a data channel, and whether it is instantiate a given subprotocol on a data channel, and whether it is
signaled in-band using DCEP or out-of-band using a non-DCEP protocol signaled in-band using DCEP or out-of-band using a non-DCEP protocol
(or both). In particular, the SDP offer generated by the RTCweb data (or both). In particular, the SDP offer generated by the RTCweb data
channel stack includes no channel-specific information. channel stack includes no channel-specific information.
This document defines SDP offer/answer 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 subprotocols,
to enable out-of-band negotiation. to enable out-of-band negotiation.
This document makes use of MSRP in many of the examples. It does not This document makes use of MSRP (Message Session Relay Protocol) in
provide a complete specification of how to negotiate the use of a many of the examples. It does not provide a complete specification
data channel to transport MSRP. Procedures specific to each sub- of how to negotiate the use of a data channel to transport MSRP.
protocol such as MSRP will be documented elsewhere. The use of MSRP Procedures specific to each subprotocol such as MSRP are documented
in some examples is only to show how the generic procedures described elsewhere. The use of MSRP in some examples is only to show how the
herein might apply to a specific sub-protocol. generic procedures described herein might apply to a specific
subprotocol.
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:
skipping to change at page 5, line 13 skipping to change at page 5, line 22
perspective of the SDP answerer, the peer is the SDP offerer. perspective of the SDP answerer, the peer is the SDP offerer.
SCTP Stream Sequence Number (SSN): the SCTP stream sequence number SCTP Stream Sequence Number (SSN): the SCTP stream sequence number
as specified in [RFC4960]. as specified in [RFC4960].
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. Applicability Statement 4. Applicability Statement
The mechanism in this specification only applies to the Session The mechanism in this document 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. SDP Offer/Answer Negotiation 5. SDP Offer/Answer Negotiation
This section defines an SDP extension by which two clients can This section defines an SDP extension by which two clients can
negotiate data channel-specific and sub-protocol-specific parameters negotiate data channel-specific and subprotocol-specific parameters
without using DCEP [I-D.ietf-rtcweb-data-protocol]. This SDP without using DCEP [I-D.ietf-rtcweb-data-protocol]. This SDP
extension only defines usage in the context of SDP offer/answer. extension only defines usage in the context of SDP offer/answer.
Appendix A provides information how data channels work in general and Appendix A provides information how data channels work in general and
especially summarizes some key aspects, which should be considered especially summarizes some key aspects, which should be considered
for the negotiation of data channels if DCEP is not used. for the negotiation of data channels if DCEP is not used.
5.1. SDP Syntax 5.1. SDP Syntax
Two new SDP attributes are defined to support SDP offer/answer Two new SDP attributes are defined to support SDP offer/answer
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 negotiation of channel-specific parameters. The second attribute
provides for negotiation of sub-protocol-specific parameters. provides for negotiation of subprotocol-specific parameters.
5.1.1. SDP Attribute for Data Channel Parameter Negotiation 5.1.1. 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 3), 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, subprotocol, label, maximal number of
delivery, and priority. retransmissions, maximal retransmission time, order of delivery, and
priority.
The intention in exchanging these attributes is to create, on two The intention in exchanging these attributes is to create, on two
peers, without use of DCEP [I-D.ietf-rtcweb-data-protocol], matched peers, without use of DCEP [I-D.ietf-rtcweb-data-protocol], matched
pairs of oppositely directed data channels having the same set of pairs of oppositely directed data channels having the same set of
attributes. It is assumed that the data channel properties attributes. It is assumed that the data channel properties
(reliable/partially reliable, ordered/unordered) are suitable per the (reliable/partially reliable, ordered/unordered) are suitable per the
sub-protocol transport requirements. subprotocol transport requirements.
5.1.1.1. dcmap Attribute 5.1.1.1. dcmap Attribute
"a=dcmap:" is a media level attribute having following ABNF syntax. "a=dcmap:" is a media level attribute having following ABNF
(Augmented Backus-Naur Form, [RFC5234]) syntax.
Formal Syntax: Formal Syntax:
Name: dcmap Name: dcmap
Value: dcmap-value Value: dcmap-value
Usage Level: media Usage Level: media
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 / priority-opt
; Either only maxretr-opt or maxtime-opt ; Either only maxretr-opt or maxtime-opt
; is present. ; is 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 = "0" / integer
I-D.ietf-rtcweb-data-protocol> ; number of retransmissions,
; number of retransmissions ; less than 2^32,
; derived from 'Reliability Parameter' of
; [I-D.ietf-rtcweb-data-protocol]
maxtime-opt = "max-time=" maxtime-value maxtime-opt = "max-time=" maxtime-value
maxtime-value = <from-Reliability-Parameter of maxtime-value = "0" / integer
I-D.ietf-rtcweb-data-protocol> ; milliseconds,
; milliseconds ; less than 2^32,
; derived from 'Reliability Parameter' of
; [I-D.ietf-rtcweb-data-protocol]
priority-opt = "priority=" priority-value
priority-value = "0" / integer
; unsigned integer value indicating the priority of
; the data channel,
; less than 2^16,
; derived from 'Priority' of
; [I-D.ietf-rtcweb-data-protocol]
quoted-string = DQUOTE *(quoted-char / escaped-char) DQUOTE quoted-string = DQUOTE *(quoted-char / escaped-char) DQUOTE
quoted-char = SP / quoted-visible quoted-char = SP / quoted-visible
quoted-visible = %21 / %23-24 / %26-7E ; VCHAR without " or % quoted-visible = %21 / %23-24 / %26-7E ; VCHAR without " or %
escaped-char = "%" HEXDIG HEXDIG escaped-char = "%" HEXDIG HEXDIG
DQUOTE = <from-RFC5234> DQUOTE = <from-RFC5234>
integer = <from-RFC5234> integer = <from-RFC4566>
Examples: Examples:
a=dcmap:0 a=dcmap:0
a=dcmap:1 subprotocol="BFCP";max-time=60000 a=dcmap:1 subprotocol="BFCP";max-time=60000;priority=512
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;priority=128
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
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 MAY be one 'maxretr-opt' parameter or one 'maxtime-opt' parameter MAY be
present. Both MUST NOT be present. present. Both MUST NOT be present.
5.1.1.2. dcmap Multiplexing Category 5.1.1.2. dcmap Multiplexing Category
Multiplexing characteristics of SDP attributes are described in Multiplexing characteristics of SDP attributes are described in
[I-D.ietf-mmusic-sdp-mux-attributes]. Various SDP attribute [I-D.ietf-mmusic-sdp-mux-attributes]. Various SDP attribute
multiplexing categories are introduced there. multiplexing categories are introduced there.
The multiplexing category of the "a=dcmap:" attribute is SPECIAL. The multiplexing category of the "a=dcmap:" attribute is SPECIAL.
As the usage of multiple SCTP associations on top of a single DTLS As the usage of multiple SCTP associations on top of a single DTLS
connection is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no connection is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no
"a=dcmap:" attribute multiplexing rules are specified for the "a=dcmap:" attribute multiplexing rules are specified for the
UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. This document does UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. This document also
also not specify multiplexing rules for this attribute for SCTP or does not specify multiplexing rules for this attribute for SCTP or
SCTP/DTLS proto values. If future extensions of SCTP/DTLS proto values. If future extensions of
[I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of [I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of
multiple SCTP associations on top of a single DTLS connection, or how multiple SCTP associations on top of a single DTLS connection, or how
to add multiple SCTP associations to one BUNDLE group, then to add multiple SCTP associations to one BUNDLE group, then
multiplexing rules for the "a=dcmap:" attribute need to be defined as multiplexing rules for the "a=dcmap:" attribute need to be defined as
well, for instance in an extension of this SDP based data channel well, for instance in an extension of this SDP based data channel
negotiation specification. negotiation specification.
5.1.1.3. dcmap-stream-id Parameter 5.1.1.3. dcmap-stream-id Parameter
The 'dcmap-stream-id' parameter indicates the SCTP stream identifier The 'dcmap-stream-id' parameter indicates the SCTP stream identifier
skipping to change at page 8, line 48 skipping to change at page 8, line 27
5.1.1.4. label Parameter 5.1.1.4. 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 [WebRtcAPI], an RTCDataChannel object from other the WebRTC API [WebRtcAPI], an RTCDataChannel object from other
RTCDataChannel objects. This parameter maps to the 'Label' parameter RTCDataChannel objects. This parameter maps to the 'Label' parameter
defined in [I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is defined in [I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is
optional. If it is not present, then its value defaults to the empty optional. If it is not present, then its value defaults to the empty
string. string.
Note: The empty string MAY also be explicitly used as 'label' value, Note: The empty string MAY also be explicitly used as a 'label'
such that 'label=""' is equivalent to the 'label' parameter not being value, such that 'label=""' is equivalent to the 'label' parameter
present at all. [I-D.ietf-rtcweb-data-protocol] allows the not being 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.
5.1.1.5. subprotocol Parameter 5.1.1.5. subprotocol Parameter
The 'subprotocol' parameter indicates which protocol the client The 'subprotocol' parameter indicates which protocol the client
expects to exchange via the channel. This parameter maps to the expects to exchange via the channel. This parameter maps to the
'Protocol' parameter defined in [I-D.ietf-rtcweb-data-protocol]. 'Protocol' parameter defined in [I-D.ietf-rtcweb-data-protocol].
Section 8.1 specifies how new sub-protocol parameter values are Section 8.1 specifies how new subprotocol parameter values are
registered. 'Subprotocol' is an optional parameter. If the registered. 'Subprotocol' is an optional parameter. If the
'subprotocol' parameter is not present, then its value defaults to 'subprotocol' parameter is not present, then its value defaults to an
the empty string. empty string.
Note: The empty string MAY also be explicitly used as 'subprotocol' Note: The empty string MAY also be explicitly used as 'subprotocol'
value, such that 'subprotocol=""' is equivalent to the 'subprotocol' value, such that 'subprotocol=""' is equivalent to the 'subprotocol'
parameter not being present at all. [I-D.ietf-rtcweb-data-protocol] parameter not being present at all. [I-D.ietf-rtcweb-data-protocol]
allows the DATA_CHANNEL_OPEN message's 'Subprotocol' value to be an allows the DATA_CHANNEL_OPEN message's 'Subprotocol' value to be an
empty string. empty string.
5.1.1.6. max-retr Parameter 5.1.1.6. max-retr Parameter
This parameter indicates that the data channel is partially reliable. This parameter indicates that the data channel is partially reliable.
skipping to change at page 10, line 5 skipping to change at page 9, line 33
The 'ordered' parameter with value "true" indicates that the receiver The 'ordered' parameter with value "true" indicates that the receiver
MUST dispatch DATA chunks in the data channel to the upper layer 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].
5.1.1.9. priority Parameter
The 'priority' parameter indicates the data channel's priority
relative to the priorities of other data channels, which may
additionally exist over the same SCTP association. The 'priority'
parameter maps to the 'Priority' parameter defined in
[I-D.ietf-rtcweb-data-protocol]. The 'priority' parameter is
optional. In the absence of this parameter "priority=256" is
assumed.
5.1.2. Other Media Level Attributes 5.1.2. Other Media Level 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 media level SDP attributes, which are either specifically other media level SDP attributes, which are either specifically
defined for or applied to the sub-protocol in use. Each of these defined for or applied to the subprotocol in use. Each of these
attributes is represented by one new attribute line, and it includes attributes is represented by one new attribute line, and it includes
the contents of a media-level SDP attribute already defined for use the contents of a media-level SDP attribute already defined for use
with this (sub-)protocol in another IETF specification. Sub-protocol with this (sub)protocol in another IETF (Internet Engineering Task
specific attributes MAY also be defined for exclusive use with data Force) document. Subprotocol specific attributes MAY also be defined
channel transport, but SHOULD use the same syntax described here for for exclusive use with data channel transport, but SHOULD use the
other sub-protocol related attributes. same syntax described here for other subprotocol related attributes.
5.1.2.1. dcsa Attribute 5.1.2.1. dcsa Attribute
Each sub-protocol related SDP attribute that would normally be used Each subprotocol related SDP attribute that would normally be used to
to negotiate the sub-protocol using SDP is replaced with an attribute negotiate the subprotocol using SDP is replaced with an attribute of
of the form "a=dcsa:stream-id original-attribute", where dcsa stands the form "a=dcsa:stream-id original-attribute", where dcsa stands for
for "data channel sub-protocol attribute", stream-id is the SCTP "data channel subprotocol attribute", stream-id is the SCTP stream
stream identifier assigned to this sub-protocol instance, and identifier assigned to this subprotocol instance, and original-
original-attribute represents the contents of the sub-protocol attribute represents the contents of the subprotocol related
related attribute to be included. attribute to be included.
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 subprotocol.
Formal Syntax: Formal Syntax:
Name: dcsa Name: dcsa
Value: dcsa-value Value: dcsa-value
Usage Level: media Usage Level: media
Charset Dependent: no Charset Dependent: no
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 where the attribute Note that the above reference to [RFC4566] defines where the
definition can be found; it does not provide any limitation on attribute definition can be found; it does not provide any limitation
support of attributes defined in other documents in accordance with on support of attributes defined in other documents in accordance
this attribute definition. Note however that not all SDP attributes with this attribute definition. Note however that not all SDP
are suitable as "a=dcsa:" parameter. [IANA-SDP-Parameters] contains attributes are suitable as a "a=dcsa:" parameter.
the lists of IANA registered session and media level or media level [IANA-SDP-Parameters] contains the lists of IANA (Internet Assigned
Numbers Authority) registered session and media level or media level
only SDP attributes. 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 the accept-types:text/plain", which specifies that this instance of the
MSRP sub-protocol being transported on the SCTP association using the MSRP subprotocol being transported on the SCTP association using the
data channel with stream id 2 accepts plain text files. data channel with 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 subprotocol specific documents.
5.1.2.2. dcsa Multiplexing Category 5.1.2.2. dcsa Multiplexing Category
The multiplexing category of the "a=dcsa:" attribute is SPECIAL. The multiplexing category of the "a=dcsa:" attribute is SPECIAL.
As the usage of multiple SCTP associations on top of a single DTLS As the usage of multiple SCTP associations on top of a single DTLS
connection is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no connection is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no
"a=dcsa:" attribute multiplexing rules are specified for the "a=dcsa:" attribute multiplexing rules are specified for the
UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. This document does UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. This document does
also not specify multiplexing rules for this attribute for SCTP or also not specify multiplexing rules for this attribute for SCTP or
skipping to change at page 11, line 39 skipping to change at page 11, line 32
multiple SCTP associations on top of a single DTLS connection, or how multiple SCTP associations on top of a single DTLS connection, or how
to add multiple SCTP associations to one BUNDLE group, then to add multiple SCTP associations to one BUNDLE group, then
multiplexing rules for the "a=dcsa:" attribute need to be defined as multiplexing rules for the "a=dcsa:" attribute need to be defined as
well, for instance in an extension of this SDP based data channel well, for instance in an extension of this SDP based data channel
negotiation specification. negotiation specification.
5.2. Procedures 5.2. Procedures
5.2.1. Managing Stream Identifiers 5.2.1. Managing Stream Identifiers
If an SDP offer/answer exchange (could be the initial or a subsequent If a SDP offer/answer exchange (could be the initial or a subsequent
one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media
description being accepted, and if this SDP offer/answer exchange description being accepted, and if this SDP offer/answer exchange
results in the establishment of a new SCTP association, then the SDP results in the establishment of a new SCTP association, then the SDP
offerer owns the even SCTP stream ids of this new SCTP association offerer owns the even SCTP stream ids of this new SCTP association
and the answerer owns the odd SCTP stream identifiers. If this "m" and the answerer owns the odd SCTP stream identifiers. If this "m"
line is removed from the signaling session (its port number set to 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 or TCP/DTLS/ 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 even and odd SCTP based "m" line is renegotiated later on, then the even and odd
SCTP stream identifier ownership is redetermined as well as described SCTP stream identifier ownership is re-determined as described above.
above.
This specification allows simultaneous use of SDP offer/answer and This document allows simultaneous use of SDP offer/answer and DCEP
DCEP negotiation. However, an SCTP stream MUST NOT be referenced in negotiation. However, an SCTP stream MUST NOT be referenced in a
a "a=dcmap:" or "a=dcsa:" attribute of an SDP offer/answer exchange "a=dcmap:" or "a=dcsa:" attribute of an SDP offer/answer exchange if
if the associated SCTP stream has already been negotiated via DCEP. the associated SCTP stream has already been negotiated via DCEP.
Stream ids that are not currently used in SDP can be used for DCEP Stream ids that are not currently used in SDP can be used for DCEP
negotiation. Stream id allocation per SDP offer/answer negotiation negotiation. Stream id allocation per SDP offer/answer negotiation
may not align with DTLS role based allocation. This could cause may not align with DTLS role based allocation. This could cause
glare conditions when one side trying to do SDP offer/answer glare conditions when one side tries to do SDP offer/answer
negotiation on a stream id while the other end trying to open a data negotiation on a stream id while the other end tries to open a data
channel on the same stream id using DCEP negotiation. To avoid these channel on the same stream id using DCEP negotiation. To avoid these
glare conditions this specification recommends that the data channel glare conditions this document recommends that the data channel stack
stack user always selects stream ids per above described SDP offer/ user always selects stream ids per the above described SDP offer/
answer rule even when DCEP negotiation is used. To avoid glare answer rule even when DCEP negotiation is used. To avoid glare
conditions, it is possible to come up with a different stream id conditions, it is possible to come up with a different stream id
allocation scheme, but such schemes are outside the scope of this allocation scheme, but such schemes are outside the scope of this
specification. document.
5.2.2. Negotiating Data Channel Parameters 5.2.2. 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 "a=dcmap:" attribute line. Conveying a partially reliable data
channel is achieved by including only one of 'max-retr' or 'max- channel is achieved by including only one of 'max-retr' or 'max-
time'. By definition max-retr and max-time are mutually exclusive, time'. By definition max-retr and max-time are mutually exclusive,
so at most one of them MAY be present in the "a=dcmap:" attribute so at most one of them MAY be present in the "a=dcmap:" attribute
line. If an SDP offer contains both of these parameters then the line. If a SDP offer contains both of these parameters then the
receiver of such an SDP offer MUST reject the SDP offer. If an SDP receiver of such an SDP offer MUST reject the SDP offer. If a SDP
answer contains both of these parameters then the offerer MAY treat answer contains both of these parameters then the offerer MAY treat
it as an error and MAY assume the associated SDP offer/answer failed it as an error and MAY assume the associated SDP offer/answer failed
and MAY take appropriate recovery actions. These recovery options and MAY take appropriate recovery actions. These recovery options
are outside the scope of this specification. are outside the scope of this document.
The SDP answer SHALL echo the same sub-protocol, 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.
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, where "ordered=true" is the mapped to SDP in the following manner, where "ordered=true" is the
skipping to change at page 14, line 9 skipping to change at page 14, line 9
data channel, as described in Section 5.1 and in Section 5.2.2. data channel, as described in Section 5.1 and in Section 5.2.2.
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 subprotocol 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 Generates an SDP answer. o Generates an SDP answer.
o Completes the SDP answer with the "a=dcmap:" and optional o Completes the SDP answer with the "a=dcmap:" and optional
"a=dcsa:" attributes needed for each SDP offer/answer negotiated "a=dcsa:" attributes needed for each SDP offer/answer negotiated
data channel, as described in Section 5.1 and in Section 5.2.2. data channel, as described in Section 5.1 and in Section 5.2.2.
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 for which the expected "a=dcmap:" o Closes any created data channels as described in Section 5.2.4 for
and "a=dcsa:" attributes are not present in the SDP answer. which the expected "a=dcmap:" and "a=dcsa:" attributes are not
present in the SDP answer.
o Applies the SDP answer. o Applies the SDP answer.
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 instantiated. For confirmation that the data channel at the peer is instantiated. For
WebRTC, this is when both data channel stacks have channel parameters WebRTC, this is when both data channel stacks have channel 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 SCTP association is established SCTP association, as soon as the SCTP association is
skipping to change at page 15, line 14 skipping to change at page 15, line 14
Note: DCEP is not used, that is neither the SDP offerer nor the SDP Note: DCEP is not used, that is neither the SDP offerer nor the SDP
answerer send an in-band DCEP DATA_CHANNEL_OPEN message. answerer send an in-band DCEP DATA_CHANNEL_OPEN message.
5.2.4. Closing a Data Channel 5.2.4. 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
negotiated via SDP offer/answer, the data channel stack always negotiated via SDP offer/answer, the data channel stack always
performs an SCTP 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 subprotocol 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
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 the answerer MUST close those data channels whose offer then the answerer MUST close those data channels whose
skipping to change at page 16, line 5 skipping to change at page 16, line 5
then the client SHOULD generate an SDP offer which excludes this then the client SHOULD generate an SDP offer which excludes this
closed data channel. closed data channel.
The application MUST also close any data channel that was negotiated The application MUST also close any data channel that was negotiated
via SDP offer/answer, for which the stream identifiers are not listed via SDP offer/answer, for which the stream identifiers are not listed
in an incoming SDP offer. in an incoming SDP offer.
A closed data channel using local close (SCTP SSN 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 subprotocol 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 SSN reset of both incoming and outgoing streams is completed). SCTP SSN reset of both incoming and outgoing streams is completed).
This restriction is to avoid the race conditions between arrival of This restriction is to avoid the race conditions between arrival of
"SDP offer which reuses stream" with "SCTP SSN reset which closes "SDP offer which reuses stream" with "SCTP SSN reset which closes
outgoing stream" at the peer. outgoing stream" at the peer.
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 5.2.5. 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 SDP offer/answer 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 SDP offer/answer or DCEP 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 "a=dcmap:" * Initial SDP answer: Either the peer does not support "a=dcmap:"
attributes or it rejected all the data channels. In either attributes or it rejected all the data channels. In either
case the offerer closes all the SDP offer/answer negotiated case the offerer closes all the SDP offer/answer negotiated
data channels that were open at the time of initial offer. The data channels that were open at the time of initial offer. The
DTLS connection and SCTP association will still be setup. DTLS connection and SCTP association will still be setup.
* Subsequent SDP answer: All the SDP offer/answer 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 SDP offer/answer or DCEP negotiation of remains open for future SDP offer/answer or DCEP negotiation of
data channels. data channels.
SDP offer or answer has no "a=dcmap:" attributes but has "a=dcsa:"
attributes.
* This is considered an error case. In this case the receiver of
such an SDP offer or answer SHOULD ignore the "a=dcsa:"
attributes and SHOULD process the SDP offer or answer as per
above case 'SDP offer has no "a=dcmap:" attributes' or case
'SDP answer has no "a=dcmap:" attributes'.
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 subprotocol
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 subprotocol
parameters to convey in the SDP answer. The number of parameters to convey in the SDP answer. The number of
"a=dcsa:" attributes in the SDP answer does not have to match "a=dcsa:" attributes in the SDP answer does not have to match
the number of "a=dcsa:" attributes in the SDP offer. the number of "a=dcsa:" attributes in the SDP offer.
6. Examples 6. 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
skipping to change at page 18, line 35 skipping to change at page 18, line 35
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 the SDP offer contains data channels for BFCP In the above example the SDP offer contains data channels for BFCP
and MSRP sub-protocols. The SDP answer rejected BFCP and accepted (Binary Floor Control Protocol) and MSRP subprotocols. The SDP
MSRP. So, the offerer should close the data channel for BFCP and answer rejected BFCP and accepted MSRP. So, the offerer closes the
both offerer and answerer may start using the MSRP data channel data channel for BFCP and both offerer and answerer may start using
(after SCTP/DTLS association is setup). The data channel with stream the MSRP data channel (after SCTP/DTLS association is setup). The
id 0 is free and can be used for future DCEP or SDP offer/answer data channel with stream id 0 is free and can be used for future DCEP
negotiation. or SDP offer/answer negotiation.
Continuing on the earlier example in Figure 1. Continuing the example in Figure 2.
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
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 33 skipping to change at page 19, line 33
a=setup:passive a=setup:passive
a=connection:existing a=connection:existing
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 2. 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 accepts opens a new MSRP data channel with stream id 4. The answerer accepts
the entire offer. As a result the offerer closes the earlier the entire offer. As a result the offerer closes the earlier
negotiated MSRP related data channel and both offerer and answerer negotiated MSRP related data channel and both offerer and answerer
may start using new the MSRP related data channel. may start using new the MSRP related data channel.
7. Security Considerations 7. 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 8. IANA Considerations
8.1. Subprotocol Identifiers 8.1. Subprotocol Identifiers
Registration of new sub-protocol identifiers is performed using the Registration of new subprotocol identifiers is performed using the
existing IANA table "WebSocket Subprotocol Name Registry". existing IANA "WebSocket Subprotocol Name Registry" table.
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.
skipping to change at page 21, line 10 skipping to change at page 21, line 10
RFC. RFC.
This document defines a new SDP media-level attribute "a=dcsa:" as This document defines a new SDP media-level attribute "a=dcsa:" as
follows: follows:
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
| Attribute name: | dcsa | | Attribute name: | dcsa |
| Type of attribute: | media | | Type of attribute: | media |
| Mux category: | SPECIAL | | Mux category: | SPECIAL |
| Charset Dependent: | No | | Charset Dependent: | No |
| Purpose: | Define data channel sub-protocol specific | | Purpose: | Define data channel subprotocol specific |
| | attributes | | | attributes |
| Appropriate values: | As defined in Section 5.1.2 | | Appropriate values: | As defined in Section 5.1.2.1 |
| Contact name: | MMUSIC Chairs | | Contact name: | MMUSIC Chairs |
| Contact e-mail: | mmusic-chairs@ietf.org | | Contact e-mail: | mmusic-chairs@ietf.org |
| Reference: | RFCXXXX | | Reference: | RFCXXXX |
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
9. Acknowledgments 9. 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 Roni Even, Christian Groves, Gunnar and Gavin Llewellyn, and to thank Roni Even, Christian Groves, Gunnar
Hellstrom, Christer Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe Hellstrom, Christer Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe
Rauschenbach for their invaluable comments. Rauschenbach for their invaluable comments.
10. CHANGE LOG 10. CHANGE LOG
10.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-05' 10.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-06'
o Changes addressing Christian Grove's WGLC review comments raised
in http://www.ietf.org/mail-archive/web/mmusic/current/
msg15357.html and http://www.ietf.org/mail-
archive/web/mmusic/current/msg15359.html.
10.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-05'
o In IANA registration Section 8.2.1 and Section 8.2.2 replacement o In IANA registration Section 8.2.1 and Section 8.2.2 replacement
of contact name and e-mail address with "MMUSIC Chairs" and of contact name and e-mail address with "MMUSIC Chairs" and
"mmusic-chairs@ietf.org". "mmusic-chairs@ietf.org".
o In Section 5.1.2.1 replacement of "Thus in the example above, the o In Section 5.1.2.1 replacement of "Thus in the example above, the
original attribute line "a=accept- types:text/plain" is original attribute line "a=accept- types:text/plain" is
represented by the attribute line "a=dcsa:2 accept-types:text/ represented by the attribute line "a=dcsa:2 accept-types:text/
plain", which specifies that this instance of MSRP being plain", which specifies that this instance of MSRP being
transported on the SCTP association using the data channel with transported on the SCTP association using the data channel with
stream id 2 accepts plain text files." with "... which specifies stream id 2 accepts plain text files." with "... which specifies
that this instance of the MSRP sub-protocol being transported that this instance of the MSRP subprotocol being transported ...".
...".
o The last paragraph of Section 5.1.2.1 started with "Note: This o The last paragraph of Section 5.1.2.1 started with "Note: This
document does not provide a complete specification ...". Removal document does not provide a complete specification ...". Removal
of "Note:" and move of this paragraph to the introduction in of "Note:" and move of this paragraph to the introduction in
Section 1 as last paragraph. Section 1 as last paragraph.
o Section 5.1.2's headline was "Sub-Protocol Specific Attributes". o Section 5.1.2's headline was "Subprotocol Specific Attributes".
Change of this headline to "Other Media Level Attributes" and Change of this headline to "Other Media Level Attributes" and
adaptations of the first paragraph of this section and the first adaptations of the first paragraph of this section and the first
paragraph of Section 5.1.2.1 in order to clarify that not only paragraph of Section 5.1.2.1 in order to clarify that not only
those attributes may be encapsulated in a "dcsa" attribute, which those attributes may be encapsulated in a "dcsa" attribute, which
are specifically defined for the sub-protocol, but that also other are specifically defined for the subprotocol, but that also other
attributes may be encapsulated if they are related to the specific attributes may be encapsulated if they are related to the specific
sub-protocol instance. subprotocol instance.
o Move of the last but one paragraph of Section 5.1.2.1 starting o Move of the last but one paragraph of Section 5.1.2.1 starting
with "The same syntax applies to ..." right in front of the formal with "The same syntax applies to ..." right in front of the formal
syntax definition of the "dcsa" attribute. syntax definition of the "dcsa" attribute.
o Modifications of the text in Section 5.1.1.2 and Section 5.1.2.2 o Modifications of the text in Section 5.1.1.2 and Section 5.1.2.2
in order not to explicitly restrict usage of the "a=dcmap:" and in order not to explicitly restrict usage of the "a=dcmap:" and
"a=dcsa:" attributes to "m" lines with proto values "UDP/DTLS/ "a=dcsa:" attributes to "m" lines with proto values "UDP/DTLS/
SCTP" or "TCP/DTLS/SCTP". SCTP" or "TCP/DTLS/SCTP".
10.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-04' 10.3. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-04'
o In Section 5.1.1.5 the first (and only) paragraph was "The o In Section 5.1.1.5 the first (and only) paragraph was "The
'subprotocol' parameter indicates which protocol the client '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 parameter. If the 'subprotocol' parameter is not present, then
its value defaults to the empty string." Replacement of this its value defaults to the empty string." Replacement of this
paragraph with following two paragraphs: paragraph with following two paragraphs:
* The 'subprotocol' parameter indicates which protocol the client * The 'subprotocol' parameter indicates which protocol the client
expects to exchange via the channel. This parameter maps to expects to exchange via the channel. This parameter maps to
the 'Protocol' parameter defined in the 'Protocol' parameter defined in
[I-D.ietf-rtcweb-data-protocol]. Section 8.1 specifies how new [I-D.ietf-rtcweb-data-protocol]. Section 8.1 specifies how new
sub-protocol parameter values are registered. 'Subprotocol' is subprotocol parameter values are registered. 'Subprotocol' is
an optional parameter. If the 'subprotocol' parameter is not an optional parameter. If the 'subprotocol' parameter is not
present, then its value defaults to the empty string. present, then its value defaults to the empty string.
* Note: The empty string MAY also be explicitly used as * Note: The empty string MAY also be explicitly used as
'subprotocol' value, such that 'subprotocol=""' is equivalent 'subprotocol' value, such that 'subprotocol=""' is equivalent
to the 'subprotocol' parameter not being present at all. to the 'subprotocol' parameter not being present at all.
[I-D.ietf-rtcweb-data-protocol] allows the DATA_CHANNEL_OPEN [I-D.ietf-rtcweb-data-protocol] allows the DATA_CHANNEL_OPEN
message's 'Subprotocol' value to be an empty string. message's 'Subprotocol' value to be an empty string.
o Addition of [I-D.ietf-mmusic-sdp-mux-attributes] to list the of o Addition of [I-D.ietf-mmusic-sdp-mux-attributes] to list the of
skipping to change at page 23, line 10 skipping to change at page 23, line 17
o Addition of new Section 5.1.1.2 describing the mux category of the o Addition of new Section 5.1.1.2 describing the mux category of the
dcmap SDP attribute. This section and the new "a=dcsa:" attribute dcmap SDP attribute. This section and the new "a=dcsa:" attribute
related mux category section are similar to the "Mux Category" related mux category section are similar to the "Mux Category"
sections of the "a=sctp-port:" and "a=max-message-size:" sections of the "a=sctp-port:" and "a=max-message-size:"
attributes in [I-D.ietf-mmusic-sctp-sdp]. attributes in [I-D.ietf-mmusic-sctp-sdp].
o Addition of new Section 5.1.2.2 describing the mux category of the o Addition of new Section 5.1.2.2 describing the mux category of the
dcsa SDP attribute. dcsa SDP attribute.
10.3. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-03' 10.4. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-03'
o In Section 1 replacement of "RTCWeb leaves it open for other o In Section 1 replacement of "RTCWeb leaves it open for other
applications to use data channels and its in-band DCEP or out-of- applications to use data channels and its in-band DCEP or out-of-
band non-DCEP protocols for creating them" with "... to use data band non-DCEP protocols for creating them" with "... to use data
channels and its in-band DCEP or other in-band or out-of-band channels and its in-band DCEP or other in-band or out-of-band
protocols for creating them". Additionally replacement of "In protocols for creating them". Additionally replacement of "In
particular, the SDP offer generated by the application includes no particular, the SDP offer generated by the application includes no
channel-specific information" with "... generated by the RTCweb channel-specific information" with "... generated by the RTCweb
data channel stack includes no channel-specific information". data channel stack includes no channel-specific information".
o Move of former section 5 ("Data Channels") to new Appendix A and o Move of former section 5 ("Data Channels") to new Appendix A and
removal of JavaScript API specific discussions from this moved removal of JavaScript API specific discussions from this moved
text (like mentioning of data channel stack specific states). text (like mentioning of data channel stack specific states).
Therefore former section 6 ("SDP Offer/Answer Negotiation") is now Therefore former section 6 ("SDP Offer/Answer Negotiation") is now
Section 5. Section 5.
o In Section 5: o In Section 5:
* Relacement of Section 5's first paragraph "This section defines * Relacement of Section 5's first paragraph "This section defines
a method of non-DCEP negotiation by which two clients can a method of non-DCEP negotiation by which two clients can
negotiate data channel-specific and sub-protocol-specific negotiate data channel-specific and subprotocol-specific
parameters, using the out-of-band SDP offer/answer exchange. parameters, using the out-of-band SDP offer/answer exchange.
This SDP extension can only be used with the SDP offer/answer This SDP extension can only be used with the SDP offer/answer
model." with "This section defines an SDP extension by which model." with "This section defines an SDP extension by which
two clients can negotiate data channel-specific and sub- two clients can negotiate data channel-specific and
protocol-specific parameters without using DCEP subprotocol-specific parameters without using DCEP
[I-D.ietf-rtcweb-data-protocol]. This SDP extension only [I-D.ietf-rtcweb-data-protocol]. This SDP extension only
defines usage in the context of SDP offer/answer." defines usage in the context of SDP offer/answer."
* Addition of new paragraph: "Appendix A provides information how * Addition of new paragraph: "Appendix A provides information how
data channels work in general and especially summarizes some data channels work in general and especially summarizes some
key aspects, which should be considered for the negotiation of key aspects, which should be considered for the negotiation of
data channels if DCEP is not used." data channels if DCEP is not used."
o In Section 5.1.1 replacement of "The intention of exchanging these o In Section 5.1.1 replacement of "The intention of exchanging these
attributes is to create data channels on both the peers with the attributes is to create data channels on both the peers with the
skipping to change at page 24, line 20 skipping to change at page 24, line 28
o In Section 5.2.1 replacement of "However, an SDP offer/answer o In Section 5.2.1 replacement of "However, an SDP offer/answer
exchange MUST NOT be initiated if the associated SCTP stream is exchange MUST NOT be initiated if the associated SCTP stream is
already negotiated via DCEP" with "However, an SCTP stream MUST already negotiated via DCEP" with "However, an SCTP stream MUST
NOT be referenced in a dcmap or dcsa attribute of an SDP offer/ NOT be referenced in a dcmap or dcsa attribute of an SDP offer/
answer exchange if the associated SCTP stream has already been answer exchange if the associated SCTP stream has already been
negotiated via DCEP". negotiated via DCEP".
o In the examples in Section 6 addition of the previously missing o In the examples in Section 6 addition of the previously missing
colons to the "a=sctp-port" attribute lines. colons to the "a=sctp-port" attribute lines.
10.4. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02' 10.5. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02'
o Move of reference [I-D.ietf-rtcweb-jsep] from the list of o Move of reference [I-D.ietf-rtcweb-jsep] from the list of
normative references to the list of informative references. normative references to the list of informative references.
o Addition of [IANA-SDP-Parameters] to the list of informative o Addition of [IANA-SDP-Parameters] to the list of informative
references and addition of following two sentences to the first references and addition of following two sentences to the first
paragraph after the ABNF definition: "Note however that not all paragraph after the ABNF definition: "Note however that not all
SDP attributes are suitable as "a=dcsa:" parameter. SDP attributes are suitable as "a=dcsa:" parameter.
[IANA-SDP-Parameters] contains the lists of IANA registered [IANA-SDP-Parameters] contains the lists of IANA registered
session and media level or media level only SDP attributes." session and media level or media level only SDP attributes."
o In the introduction replacement of last sentence "This document o In the introduction replacement of last sentence "This document
defines SDP-based out-of-band negotiation procedures to establish defines SDP-based out-of-band negotiation procedures to establish
data channels for transport of well-defined sub-protocols" with data channels for transport of well-defined subprotocols" with
"This document defines SDP offer/answer negotiation procedures to "This document defines SDP offer/answer negotiation procedures to
establish data channels for transport of well-defined sub- establish data channels for transport of well-defined
protocols, to enable out-of-band negotiation". subprotocols, to enable out-of-band negotiation".
o Throughout the document replacement of "external negotiation" with o Throughout the document replacement of "external negotiation" with
"SDP offer/answer negotiation" and removal of term "external "SDP offer/answer negotiation" and removal of term "external
negotiation" from the terminology list in Section 3. negotiation" from the terminology list in Section 3.
o Throughout the document replacement of "internal negotiation" with o Throughout the document replacement of "internal negotiation" with
"DCEP" and removal of terms "internal negotiation" and "in-band "DCEP" and removal of terms "internal negotiation" and "in-band
negotiation" from the terminology list in Section 3. negotiation" from the terminology list in Section 3.
o Addition of "SCTP Stream Sequence Number (SSN)" to the list of o Addition of "SCTP Stream Sequence Number (SSN)" to the list of
skipping to change at page 25, line 21 skipping to change at page 25, line 31
a=dcmap". a=dcmap".
o Move of reference [WebRtcAPI] from list of normative references to o Move of reference [WebRtcAPI] from list of normative references to
list of informative references. list of informative references.
o Removal of almost all text parts, which discussed JavaScript or o Removal of almost all text parts, which discussed JavaScript or
other API specific aspects. Such API specific aspects were mainly other API specific aspects. Such API specific aspects were mainly
discussed in sub-sections of Section 5 and Section 5 of draft- discussed in sub-sections of Section 5 and Section 5 of draft-
ietf-mmusic-data-channel-sdpneg-02. ietf-mmusic-data-channel-sdpneg-02.
10.5. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01' 10.6. 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 8.1 "Subprotocol identifiers" as o Addition of new Section 8.1 "Subprotocol identifiers" as
subsection of the "IANA Considerations" related Section 8. Also subsection of the "IANA Considerations" related Section 8. 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 5.2.2: o In Section 5.2.2:
skipping to change at page 27, line 29 skipping to change at page 27, line 36
* 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 5.1.2 addition of following note after the formal o In Section 5.1.2 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."
10.6. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00' 10.7. 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 27, line 51 skipping to change at page 28, line 11
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 5.1.1 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 5.1.1.1. 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 subprotocol 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 subprotocol."
o In Section 5.1.1 removal of following note: "Note: This attribute o In Section 5.1.1 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 5.1.1.1: "dcmap is a media level attribute having
following ABNF syntax:" following ABNF syntax:"
skipping to change at page 30, line 14 skipping to change at page 30, line 22
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 5.1.1 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 5.2.2 and moval of reliability negotiation related text to
this new section. this new section.
10.7. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02' 10.8. 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 31, line 16 skipping to change at page 31, line 24
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.
10.8. Changes against '-01' 10.9. 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.
10.9. Changes against '-00' 10.10. 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 33, line 5 skipping to change at page 33, line 9
[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., Ed., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007, RFC 4960, DOI 10.17487/RFC4960, September 2007,
<http://www.rfc-editor.org/info/rfc4960>. <http://www.rfc-editor.org/info/rfc4960>.
[RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
"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
for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
DOI 10.17487/RFC4976, September 2007,
<http://www.rfc-editor.org/info/rfc4976>.
[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
and P. Kyzivat, "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
DOI 10.17487/RFC5547, May 2009,
<http://www.rfc-editor.org/info/rfc5547>.
[RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model
for the Message Session Relay Protocol (MSRP)", RFC 6135,
DOI 10.17487/RFC6135, February 2011,
<http://www.rfc-editor.org/info/rfc6135>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011,
<http://www.rfc-editor.org/info/rfc6455>.
[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message
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-12
(work in progress), October 2015.
[IANA-SDP-Parameters] [IANA-SDP-Parameters]
"Session Description Protocol (SDP) Parameters", Internet "Session Description Protocol (SDP) Parameters", Internet
Assigned Numbers Authority Protocol Assignments Session Assigned Numbers Authority Protocol Assignments Session
Description Protocol (SDP) Parameters, Description Protocol (SDP) Parameters,
<http://www.iana.org/assignments/sdp-parameters/ <http://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xhtml>. sdp-parameters.xhtml>.
[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
skipping to change at page 34, line 20 skipping to change at page 33, line 31
<http://www.w3.org/TR/2015/WD-webrtc-20150210/>. <http://www.w3.org/TR/2015/WD-webrtc-20150210/>.
Appendix A. Generic Data Channel Negotiation Aspects When Not Using Appendix A. Generic Data Channel Negotiation Aspects When Not Using
DCEP DCEP
This appendix summarizes how data channels work in general and This appendix summarizes how data channels work in general and
discusses some key aspects, which should be considered for the out- discusses some key aspects, which should be considered for the out-
of-band negotiation of data channels if DCEP is not used. of-band negotiation of data channels if DCEP is not used.
A WebRTC application creates a data channel by providing a number of A WebRTC application creates a data channel by providing a number of
setup parameters (sub-protocol, label, reliability, order of setup parameters (subprotocol, label, maximal number of
delivery, priority). The application also specifies if it wants to retransmissions, maximal retransmission time, order of delivery,
make use of the negotiation using the DCEP priority). The application also specifies if it wants to make use of
[I-D.ietf-rtcweb-data-protocol], or if the application intends to the negotiation using the DCEP [I-D.ietf-rtcweb-data-protocol], or if
negotiate data channels using the SDP offer/answer protocol. the application intends to negotiate data channels using the SDP
offer/answer protocol.
In any case, the SDP offer generated by the application is per In any case, the SDP offer generated by the application 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: the SCTP association on top of which data channels will run:
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 application will only use "m" line format "webrtc- Note: A WebRTC application 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 only one SCTP association to be established on top of a DTLS
association. association.
Note: Above SDP media description does not contain any channel- Note: The above SDP media description does not contain any channel-
specific information. specific information.
A.1. Stream Identifier Numbering A.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 data channel stack the creating a data channel can either pass to the data channel stack the
stream identifier to assign to the data channel or else let the data stream identifier to assign to the data channel or else let the data
channel stack pick one identifier from the ones unused. channel stack pick one identifier from the unused ones.
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 with the DCEP, 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
skipping to change at page 35, line 27 skipping to change at page 34, line 38
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
For data channels negotiated via some protocol different from For data channels negotiated via some protocol different from
DCEP, no convention is defined by default. DCEP, no convention is defined by default.
A.2. Generic Data Channel Negotiation Not Using DCEP A.2. Generic Data Channel Negotiation Not Using DCEP
A.2.1. Overview A.2.1. Overview
DCEP 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
protocol specific parameters. DCEP-less data channel negotiation can subprotocol specific parameters. DCEP-less data channel negotiation
be defined to allow negotiation of parameters beyond those handled by can be defined to allow negotiation of parameters beyond those
DCEP, e.g., parameters specific to the sub-protocol instantiated on a handled by DCEP, e.g., parameters specific to the subprotocol
particular data channel. instantiated on a particular data channel.
The following procedures are common to all methods of data channel The following procedures are common to all methods of data channel
negotiation not using DCEP, whether in-band (communicated using negotiation not using DCEP, whether in-band (communicated using
proprietary means on an already established data channel) or out-of- proprietary means on an already established data channel) or out-of-
band (using SDP offer/answer or some other protocol associated with band (using SDP offer/answer or some other protocol associated with
the signaling channel). the signaling channel).
A.2.2. Opening a Data Channel A.2.2. Opening a Data Channel
In the case of DCEP-less negotiation, the endpoint application has In the case of DCEP-less negotiation, the endpoint application has
the option to fully control the stream identifier assignments. the option to fully control the stream identifier assignments.
However these assignments have to coexist with the assignments However these assignments have to coexist with the assignments
controlled by the data channel stack for the DCEP negotiated data controlled by the data channel stack for the DCEP negotiated data
channels (if any). It is the responsibility of the application to channels (if any). It is the responsibility of the application to
ensure consistent assignment of stream identifiers. ensure 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 DCEP-less negotiation, the data channel stack creates be set up via DCEP-less 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. However, even if the ICE, DTLS and SCTP procedures message in-band. However, even if the ICE (Interactive Connectivity
were already successfully completed, the application can't send data Establishment), DTLS and SCTP procedures were already successfully
on this data channel until the negotiation is complete with the peer. completed, the application can't send data on this data channel until
This is because the peer needs to be aware of and accept the usage of the negotiation is complete with the peer. This is because the peer
this data channel. The peer, after accepting the data channel offer, needs to be aware of and accept the usage of this data channel. The
can start sending data immediately. This implies that the offerer peer, after accepting the data channel offer, can start sending data
may receive data channel sub-protocol messages before the negotiation immediately. This implies that the offerer may receive data channel
is complete and the application should be ready to handle it. subprotocol messages before the negotiation is complete and the
application should be ready to handle it.
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.
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 may be used on the fly as needed just by communicating data channels may be used on the fly as needed just by communicating
via non-DCEP means or by even having some local configuration/ via non-DCEP means or by even having some local configuration/
assumptions on both the peers. assumptions on both the peers.
The application then negotiates the data channel properties and sub- The application then negotiates the data channel properties and
protocol properties with the peer's application using a mechanism subprotocol properties with the peer's application using a mechanism
different from DCEP. different from DCEP.
The peer then symmetrically creates a data channel with these The peer then symmetrically creates a data channel with these
negotiated data channel properties. This is the only way for the negotiated data channel properties. This is the only way for the
peer's data channel stack to know which properties to apply when peer's data channel stack to know which properties to apply when
transmitting data on this channel. The data channel stack must allow transmitting data on this channel. The data channel stack must allow
data channel creation with any non-conflicting stream identifier so data channel creation with any non-conflicting stream identifier so
that both peers can create the data channel with the same stream that both peers can create the data channel with the same stream
identifier. identifier.
A.2.3. Closing a Data Channel A.2.3. Closing a Data Channel
When the application requests the closing of a data channel When the application requests the closing of a data channel
negotiated without DCEP, the data channel stack always performs an negotiated without DCEP, the data channel stack always performs an
SCTP SSN reset for this channel. SCTP SSN reset for this channel.
Depending upon the method used for DCEP-less negotiation and the sub- Depending upon the method used for DCEP-less negotiation and the
protocol associated with the data channel, the closing might in subprotocol associated with the data channel, the closing might in
addition be signaled to the peer via SDP offer/answer negotiation. addition be signaled to the peer via SDP offer/answer negotiation.
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
Maridi R. Makaraju (Raju) Maridi R. Makaraju (Raju)
Alcatel-Lucent Alcatel-Lucent
 End of changes. 102 change blocks. 
217 lines changed or deleted 232 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/