draft-ietf-mmusic-data-channel-sdpneg-15.txt   draft-ietf-mmusic-data-channel-sdpneg-16.txt 
MMUSIC K. Drage MMUSIC K. Drage
Internet-Draft Unaffiliated Internet-Draft Unaffiliated
Intended status: Standards Track M. Makaraju Intended status: Standards Track M. Makaraju
Expires: June 7, 2018 Nokia Expires: June 28, 2018 Nokia
J. Stoetzer-Bradler J. Stoetzer-Bradler
R. Ejzak R. Ejzak
J. Marcon J. Marcon
Unaffiliated Unaffiliated
R. Even, Ed. R. Even, Ed.
Huawei Huawei
December 4, 2017 December 25, 2017
SDP-based Data Channel Negotiation SDP-based Data Channel Negotiation
draft-ietf-mmusic-data-channel-sdpneg-15 draft-ietf-mmusic-data-channel-sdpneg-16
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 (Stream Control Transmission Protocol), where each channels over SCTP (Stream Control Transmission Protocol), where each
data channel might be used to transport other protocols, called data channel might be used to transport other protocols, called
skipping to change at page 2, line 7 skipping to change at page 2, line 7
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 7, 2018. This Internet-Draft will expire on June 28, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 6
5. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 6 5. SDP Data Channel attributes . . . . . . . . . . . . . . . . . 6
5.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. SDP data channel attributes . . . . . . . . . . . . . . . 6
5.1.1. SDP Attribute for Data Channel Parameter Negotiation 6 5.1.1. SDP Attribute for Data Channel Parameter Negotiation 6
5.1.2. Other Media Level Attributes . . . . . . . . . . . . 10 5.1.2. Other Media Level Attributes . . . . . . . . . . . . 10
5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12 6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 12
5.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 12 6.1. Managing Stream Identifiers . . . . . . . . . . . . . . . 12
5.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13 6.2. Negotiating Data Channel Parameters . . . . . . . . . . . 13
5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14 6.3. Generating initial Offer . . . . . . . . . . . . . . . . 14
5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16 6.4. Generating SDP answer . . . . . . . . . . . . . . . . . . 15
5.2.5. Various SDP Offer/Answer Scenarios and Considerations 17 6.5. Offerer Processing of the SDP Answer . . . . . . . . . . 15
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.6. Closing a Data Channel . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 6.7. Various SDP Offer/Answer Scenarios and Considerations . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 21 8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 21 9.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 22
8.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 22 9.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 22
8.3. New Usage Level . . . . . . . . . . . . . . . . . . . . . 22 9.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 22
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 9.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 23
10. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 23 9.3. New Usage Level . . . . . . . . . . . . . . . . . . . . . 23
10.1. Changes against 'draft-ietf-mmusic-data-channel- 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
sdpneg-14' . . . . . . . . . . . . . . . . . . . . . . . 23 11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1. Changes against 'draft-ietf-mmusic-data-channel-
10.2. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-15' . . . . . . . . . . . . . . . . . . . . . . . 24
sdpneg-12' . . . . . . . . . . . . . . . . . . . . . . . 23 11.2. Changes against 'draft-ietf-mmusic-data-channel-
10.3. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-14' . . . . . . . . . . . . . . . . . . . . . . . 24
sdpneg-11' . . . . . . . . . . . . . . . . . . . . . . . 23 11.3. Changes against 'draft-ietf-mmusic-data-channel-
10.4. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-12' . . . . . . . . . . . . . . . . . . . . . . . 24
sdpneg-10' . . . . . . . . . . . . . . . . . . . . . . . 24 11.4. Changes against 'draft-ietf-mmusic-data-channel-
10.5. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-11' . . . . . . . . . . . . . . . . . . . . . . . 24
sdpneg-09' . . . . . . . . . . . . . . . . . . . . . . . 24 11.5. Changes against 'draft-ietf-mmusic-data-channel-
10.6. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-10' . . . . . . . . . . . . . . . . . . . . . . . 25
sdpneg-08' . . . . . . . . . . . . . . . . . . . . . . . 25 11.6. Changes against 'draft-ietf-mmusic-data-channel-
10.7. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-09' . . . . . . . . . . . . . . . . . . . . . . . 25
sdpneg-07' . . . . . . . . . . . . . . . . . . . . . . . 25 11.7. Changes against 'draft-ietf-mmusic-data-channel-
10.8. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-08' . . . . . . . . . . . . . . . . . . . . . . . 26
sdpneg-06' . . . . . . . . . . . . . . . . . . . . . . . 25 11.8. Changes against 'draft-ietf-mmusic-data-channel-
10.9. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-07' . . . . . . . . . . . . . . . . . . . . . . . 26
sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 25 11.9. Changes against 'draft-ietf-mmusic-data-channel-
10.10. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-06' . . . . . . . . . . . . . . . . . . . . . . . 26
sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 26 11.10. Changes against 'draft-ietf-mmusic-data-channel-
10.11. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 26
sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 27 11.11. Changes against 'draft-ietf-mmusic-data-channel-
10.12. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 27
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 28 11.12. Changes against 'draft-ietf-mmusic-data-channel-
10.13. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 28
sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 29 11.13. Changes against 'draft-ietf-mmusic-data-channel-
10.14. Changes against 'draft-ietf-mmusic-data-channel- sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 29
sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 31 11.14. Changes against 'draft-ietf-mmusic-data-channel-
10.15. Changes against 'draft-ejzak-mmusic-data-channel- sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 30
sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 34 11.15. Changes against 'draft-ietf-mmusic-data-channel-
10.16. Changes against '-01' . . . . . . . . . . . . . . . . . 35 sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 32
10.17. Changes against '-00' . . . . . . . . . . . . . . . . . 35 11.16. Changes against 'draft-ejzak-mmusic-data-channel-
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 35
11.1. Normative References . . . . . . . . . . . . . . . . . . 36 11.17. Changes against '-01' . . . . . . . . . . . . . . . . . 36
11.2. Informative References . . . . . . . . . . . . . . . . . 37 11.18. Changes against '-00' . . . . . . . . . . . . . . . . . 36
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 37
12.1. Normative References . . . . . . . . . . . . . . . . . . 37
12.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Generic Data Channel Negotiation Aspects When Not Appendix A. Generic Data Channel Negotiation Aspects When Not
Using DCEP . . . . . . . . . . . . . . . . . . . . . 37 Using DCEP . . . . . . . . . . . . . . . . . . . . . 39
A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 38 A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 39
A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 39 A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 40
A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 39 A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 40
A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 39 A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 40
A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 40 A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
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 the Stream Control Transmission data channels running on top of the Stream Control Transmission
Protocol (SCTP). RTCWeb allows applications to use data channels. Protocol (SCTP) [I-D.ietf-rtcweb-data-channel]. RTCWeb allows
RTCWeb defines an in-band Data Channel Establishment Protocol (DCEP), applications to use data channels. RTCWeb defines an in-band Data
however other in-band or out-of-band protocols may be used for Channel Establishment Protocol (DCEP)
establishing data channels. Each data channel consists of paired [I-D.ietf-rtcweb-data-protocol], however other in-band or out-of-band
SCTP streams sharing the same SCTP Stream Identifier. Data channels protocols may be used for establishing data channels. Each data
are created by endpoint applications through the WebRTC API channel consists of paired SCTP streams sharing the same SCTP Stream
(Application Programming Interface), or other users of a data channel Identifier. Data channels are created by endpoint applications
like CLUE. They can be used to transport proprietary or well-defined through the WebRTC API (Application Programming Interface), or other
protocols, which in the latter case can be signaled by the data users of a data channel like CLUE [I-D.ietf-clue-datachannel] They
channel "subprotocol" parameter, conceptually similar to the can be used to transport proprietary or well-defined protocols, which
WebSocket "subprotocol". However, apart from the "subprotocol" value in the latter case can be signaled by the data channel "subprotocol"
transmitted to the peer, RTCWeb leaves it open how endpoint parameter, conceptually similar to the WebSocket "subprotocol".
applications can agree on how to instantiate a given subprotocol on a However, apart from the "subprotocol" value transmitted to the peer,
data channel, and whether it is signaled in-band using DCEP or out- RTCWeb leaves it open how endpoint applications can agree on how to
of-band using a non-DCEP protocol (or both). In particular, the SDP instantiate a given subprotocol on a data channel, and whether it is
offer generated by the RTCweb data channel stack includes no channel- signaled in-band using DCEP or out-of-band using a non-DCEP protocol
specific information. (or both). In particular, the SDP offer generated by the RTCweb data
channel stack includes no channel-specific information.
This document defines SDP offer/answer negotiation procedures to This document defines SDP offer/answer [RFC3264] negotiation
establish data channels for transport of well-defined subprotocols, procedures to establish data channels for transport of well-defined
to enable out-of-band negotiation. These procedures are based on subprotocols, to enable out-of-band negotiation. These procedures
generic SDP offer/answer negotiation rules for SCTP based media are based on generic SDP offer/answer negotiation rules for SCTP
transport as specified in [I-D.ietf-mmusic-sctp-sdp] for the SDP "m" based media transport as specified in [I-D.ietf-mmusic-sctp-sdp] for
line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. In the future, the SDP "m" line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. In
data channels could be defined over other SCTP based protocols, such the future, data channels could be defined over other SCTP based
as SCTP over IP. However, corresponding potential other "m" line protocols, such as SCTP over IP. However, corresponding potential
proto values are not considered in this document. other "m=" line proto values are not considered in this document.
This document makes use of MSRP (Message Session Relay Protocol) and This document makes use of MSRP (Message Session Relay Protocol) and
BFCP (Binary Floor Control Protocol) in many of the examples. It BFCP (Binary Floor Control Protocol) in many of the examples. It
does not provide a complete specification of how to negotiate the use does not provide a complete specification of how to negotiate the use
of a data channel to transport MSRP. Procedures specific to each of a data channel to transport MSRP. Procedures specific to each
subprotocol such as MSRP are documented elsewhere. The use of MSRP subprotocol would have to be documented elsewhere. For MSRP they are
in some examples is only to show how the generic procedures described documented in [I-D.ietf-mmusic-msrp-usage-data-channel] . The use of
herein might apply to a specific subprotocol. MSRP in some examples is only to show how the 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 6, line 7 skipping to change at page 6, line 15
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 document 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 Data Channel attributes
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 subprotocol-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 data channel attributes
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 subprotocol-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 This section defines a new media level attribute "a=dcmap:" that
for data channels (defined in Section 3), each SDP offer and answer defines the data channel parameters for each data channel to be
includes one "a=dcmap:" attribute that defines the data channel negotiated. The attribute specifies the following parameters for a
parameters for each data channel to be negotiated. Each such data channel: SCTP stream identifier, subprotocol, label, maximal
attribute line specifies the following parameters for a data channel: number of retransmissions, maximal retransmission time, 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 this attribute 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 data channels as pairs of oppositely directed SCTP streams having the
attributes. It is assumed that the data channel properties same set of attributes. It is assumed that the data channel
(reliable/partially reliable, ordered/unordered) are suitable per the properties (reliable/partially reliable, ordered/unordered) are
subprotocol transport requirements. suitable per the 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 "a=dcmap:" is a media level attribute having following ABNF
(Augmented Backus-Naur Form, [RFC5234]) syntax. (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) ]
skipping to change at page 8, line 22 skipping to change at page 8, line 31
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].
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
association is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no association 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. If future extensions UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. If future extensions
of [I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of of [I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of
multiple SCTP associations on top of a single DTLS association, or multiple SCTP associations on top of a single DTLS association, or
how to add multiple SCTP associations to one BUNDLE group, then how 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 offer/answer based
negotiation specification. data channel 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
within the SCTP association used to form the data channel. within the SCTP association used to form the data channel.
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
skipping to change at page 9, line 15 skipping to change at page 9, line 25
Note: The empty string MAY also be explicitly used as a 'label' Note: The empty string MAY also be explicitly used as a 'label'
value, such that 'label=""' is equivalent to the 'label' parameter value, such that 'label=""' is equivalent to the 'label' parameter
not being 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 subprotocol parameter values are Section 9.1 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 an 'subprotocol' parameter is not present, then its value defaults to an
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.
skipping to change at page 10, line 22 skipping to change at page 10, line 32
The 'priority' parameter indicates the data channel's priority The 'priority' parameter indicates the data channel's priority
relative to the priorities of other data channels, which may relative to the priorities of other data channels, which may
additionally exist over the same SCTP association. The 'priority' additionally exist over the same SCTP association. The 'priority'
parameter maps to the 'Priority' parameter defined in parameter maps to the 'Priority' parameter defined in
[I-D.ietf-rtcweb-data-protocol]. The 'priority' parameter is [I-D.ietf-rtcweb-data-protocol]. The 'priority' parameter is
optional. In the absence of this parameter "priority=256" is optional. In the absence of this parameter "priority=256" is
assumed. 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 media description, each data channel declaration MAY also
other media level SDP attributes, which are either specifically be followed by other media level SDP attributes, which are either
defined for or applied to the subprotocol in use. Each of these specifically defined for or applied to the subprotocol in use. Each
attributes is represented by one new attribute line, and it includes of these attributes is represented by one new attribute line, and it
the contents of a media-level SDP attribute already defined for use includes the contents of a media-level SDP attribute already defined
with this (sub)protocol in another IETF (Internet Engineering Task for use with this (sub)protocol in another IETF (Internet Engineering
Force) document. Subprotocol specific attributes MAY also be defined Task Force) document. Subprotocol specific attributes MAY also be
for exclusive use with data channel transport, but MUST use the same defined for exclusive use with data channel transport, but MUST use
syntax described here for other subprotocol related attributes. the same syntax described here for other subprotocol related
attributes.
5.1.2.1. dcsa Attribute 5.1.2.1. dcsa Attribute
Each SDP attribute, related to the subprotocol, that would normally Each SDP attribute, related to the subprotocol, that would normally
be used to negotiate the subprotocol using SDP is replaced with an be used to negotiate the subprotocol using SDP offer/answer is
attribute of the form "a=dcsa:stream-id original-attribute", where replaced with an attribute of the form "a=dcsa:stream-id original-
dcsa stands for "data channel subprotocol attribute", stream-id is attribute", where dcsa stands for "data channel subprotocol
the SCTP stream identifier assigned to this subprotocol instance, and attribute", stream-id is the SCTP stream identifier assigned to this
original-attribute represents the contents of the subprotocol related subprotocol instance, and original-attribute represents the contents
attribute to be included. of the subprotocol related 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 subprotocol. negotiation of this instance of the subprotocol.
Formal Syntax: Formal Syntax:
Name: dcsa Name: dcsa
Value: dcsa-value Value: dcsa-value
skipping to change at page 12, line 7 skipping to change at page 12, line 10
attributes are used in the same way as defined in the original attributes are used in the same way as defined in the original
subprotocol specification, also if the subprotocol is transported subprotocol specification, also if the subprotocol is transported
over a data channel and if the attribute is correspondingly embedded over a data channel and if the attribute is correspondingly embedded
in a "a=dcsa" attribute. in a "a=dcsa" attribute.
There may be cases, where the usage of a subprotocol related media There may be cases, where the usage of a subprotocol related media
level attribute depends on the subprotocol's transport protocol. In level attribute depends on the subprotocol's transport protocol. In
such cases the subprotocol related usage of the attribute is expected such cases the subprotocol related usage of the attribute is expected
to be described for the data channel transport. A data channel to be described for the data channel transport. A data channel
specific usage of a subprotocol attribute is expected to be specified specific usage of a subprotocol attribute is expected to be specified
in the same document, that registers the subprotocol's identifier for in the same document that registers the subprotocol's identifier for
data channel usage as described in Section 8.1. data channel usage as described in Section 9.1.
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
association is outside the scope of [I-D.ietf-mmusic-sctp-sdp], no association 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. If future extensions UDP/DTLS/SCTP and TCP/DTLS/SCTP proto values. If future extensions
of [I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of of [I-D.ietf-mmusic-sctp-sdp] define how to negotiate multiplexing of
multiple SCTP associations on top of a single DTLS association, or multiple SCTP associations on top of a single DTLS association, or
how to add multiple SCTP associations to one BUNDLE group, then how 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 6. SDP Offer/Answer Procedures
5.2.1. Managing Stream Identifiers 6.1. Managing Stream Identifiers
If a 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 re-determined as described above. SCTP stream identifier ownership is re-determined as described above.
This document allows simultaneous use of SDP offer/answer and DCEP This document allows simultaneous use of SDP offer/answer and DCEP
negotiation. However, an SCTP stream MUST NOT be referenced in a negotiation. However, an SCTP stream MUST NOT be referenced in a
"a=dcmap:" or "a=dcsa:" attribute of an SDP offer/answer exchange if "a=dcmap:" or "a=dcsa:" attribute of an SDP offer/answer exchange 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 offer/answer can be
negotiation. Stream id allocation per SDP offer/answer negotiation used for DCEP negotiation. Stream id allocation per SDP offer/answer
may not align with DTLS role based allocation. This could cause negotiation may not align with DTLS role based allocation. This
glare conditions when one side tries to do SDP offer/answer could cause glare conditions when one side tries to do SDP offer/
negotiation on a stream id while the other end tries to open a data answer negotiation on a stream id while the other end tries to open a
channel on the same stream id using DCEP negotiation. To avoid these data channel on the same stream id using DCEP negotiation. To avoid
glare conditions this document recommends that the data channel stack these glare conditions this document recommends that the data channel
user always selects stream ids per the above described SDP offer/ stack user always selects stream ids per the above described SDP
answer rule even when DCEP negotiation is used. To avoid glare offer/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
document. document.
5.2.2. Negotiating Data Channel Parameters 6.2. 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 a 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 a SDP receiver of such an SDP offer MUST reject the SDP offer. If a SDP
answer contains both of these parameters then the offerer MUST treat answer contains both of these parameters then the offerer MUST treat
skipping to change at page 13, line 34 skipping to change at page 13, line 36
The SDP answer SHALL echo the same subprotocol, max-retr, max-time, The SDP answer SHALL echo the same subprotocol, max-retr, max-time,
ordered parameters, if those were present in the offer, and MAY ordered parameters, if those were present in the offer, and MAY
include a label parameter. They MAY appear in any order, which could include a label parameter. They MAY appear in any order, which could
be different from the SDP offer, in the SDP answer. be different from the SDP offer, in the SDP answer.
When sending a subsequent offer or an answer, and for as long as the When sending a subsequent offer or an answer, and for as long as the
data channel is still open, the sender MUST replicate the same data channel is still open, the sender MUST replicate the same
information. information.
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 media description in the following manner, where
default and may be omitted: "ordered=true" is the default and may be omitted:
DATA_CHANNEL_RELIABLE DATA_CHANNEL_RELIABLE
ordered=true ordered=true
DATA_CHANNEL_RELIABLE_UNORDERED DATA_CHANNEL_RELIABLE_UNORDERED
ordered=false ordered=false
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT
ordered=true;max-retr=<number of retransmissions> ordered=true;max-retr=<number of retransmissions>
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED
ordered=false;max-retr=<number of retransmissions> ordered=false;max-retr=<number of retransmissions>
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED
ordered=true;max-time=<lifetime in milliseconds> ordered=true;max-time=<lifetime in milliseconds>
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED
ordered=false;max-time=<lifetime in milliseconds> ordered=false;max-time=<lifetime in milliseconds>
5.2.3. Opening a Data Channel 6.3. Generating initial Offer
The procedure for opening a data channel using SDP offer/answer The procedure for opening a data channel using SDP offer/answer
negotiation starts with the agent preparing to send an SDP offer. If negotiation starts with the agent preparing to send an SDP offer. If
a peer receives an SDP offer before starting to send a new SDP offer a peer receives an SDP offer before starting to send a new SDP offer
with data channels that are to be SDP offer/answer negotiated, or with data channels that are to be SDP offer/answer negotiated, or
loses an SDP offer glare resolution procedure in this case, it MUST loses an SDP offer glare resolution procedure in this case, it MUST
wait until the ongoing SDP offer/answer completes before resuming the wait until the ongoing SDP offer/answer completes before resuming the
SDP offer/answer negotiation procedure. SDP offer/answer negotiation procedure.
The agent that intends to send an SDP offer to create data channels The agent that intends to send an SDP offer to create data channels
through SDP offer/answer negotiation performs the following: through SDP offer/answer negotiation performs the following:
o Creates data channels using stream identifiers from the owned set o Creates data channels using stream identifiers from the owned set
(see Section 5.2.1). (see Section 6.1).
o Generates a new SDP offer. o Generates a new SDP offer.
o Determines the list of stream identifiers assigned to data o Determines the list of stream identifiers assigned to data
channels opened through SDP offer/answer negotiation. channels opened through SDP offer/answer negotiation.
o Completes the SDP offer with the "a=dcmap:" and "a=dcsa:" o Completes the SDP offer with the "a=dcmap:" and "a=dcsa:"
attributes needed, if any, for each SDP offer/answer negotiated attributes needed, if any, 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 6.2.
o If it adds "a=dcsa" attributes to the SDP offer, then it SHOULD o If it adds "a=dcsa" attributes to the SDP offer, then it SHOULD
add the subprotocol parameter to the "a=dcmap" attribute with a add the subprotocol parameter to the "a=dcmap" attribute with a
non-empty subprotocol identifier. non-empty subprotocol identifier.
o Sends the SDP offer. o Sends the SDP offer.
6.4. Generating SDP answer
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, taking into account the o Parses and applies the SDP offer, taking into account the
considerations discussed in Section 5.2.5. considerations discussed in Section 6.7.
o Analyzes the channel parameters and subprotocol 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, the agent MUST create peer instances o For accepted data channels, the agent MUST create peer instances
for the data channels using the SCTP stream identifiers and for the data channels using the SCTP stream identifiers and
channel parameters contained in the SDP offer. channel parameters contained in the SDP offer.
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 6.2.
o Sends the SDP answer. o Sends the SDP answer.
6.5. Offerer Processing of 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 as described in Section 5.2.4 for o Closes any created data channels as described in Section 6.6 for
which the expected "a=dcmap:" and "a=dcsa:" attributes are not which the expected "a=dcmap:" and "a=dcsa:" attributes are not
present in the SDP answer. 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:
skipping to change at page 16, line 8 skipping to change at page 16, line 11
o At the agent sending an SDP offer to create a new SDP offer/answer o At the agent sending an SDP offer to create a new SDP offer/answer
negotiated data channel for which there is an established SCTP negotiated data channel for which there is an established SCTP
association, when it receives the SDP answer confirming acceptance association, when it receives the SDP answer confirming acceptance
of the data channel or when it begins to receive data on the data of the data channel or when it begins to receive data on the data
channel from the peer, whichever occurs first. channel from the peer, whichever occurs first.
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 6.6. 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 subprotocol 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
skipping to change at page 17, line 12 skipping to change at page 17, line 19
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 subprotocol 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 6.7. 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
association and SCTP association is negotiated and, if agreed, association 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 to be closed now. The DTLS/SCTP channels are expected to be closed now. The DTLS/SCTP
association remains open for SDP offer/answer or DCEP association remains open for SDP offer/answer or DCEP
skipping to change at page 18, line 25 skipping to change at page 18, line 30
* The receiver of such an SDP offer or answer SHOULD ignore this * The receiver of such an SDP offer or answer SHOULD ignore this
entire "a=dcsa" attribute line. entire "a=dcsa" attribute line.
SDP offer or answer has an "a=dcsa" attribute, whose subprotocol SDP offer or answer has an "a=dcsa" attribute, whose subprotocol
attribute is known, but whose subprotocol attribute semantic is attribute is known, but whose subprotocol attribute semantic is
not known for the data channel transport case. not known for the data channel transport case.
* The receiver of such an SDP offer or answer SHOULD ignore this * The receiver of such an SDP offer or answer SHOULD ignore this
entire "a=dcsa" attribute line. entire "a=dcsa" attribute line.
6. Examples 7. Examples
SDP offer: SDP offer:
m=application 10001 UDP/DTLS/SCTP webrtc-datachannel m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
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=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
a=tls-id:abc3de65cddef001be82 a=tls-id:abc3de65cddef001be82
skipping to change at page 20, line 42 skipping to change at page 21, line 42
Figure 3: Example 3 Figure 3: Example 3
The above example is a continuation of the example in Figure 2. The The above example is a continuation of the example in Figure 2. The
SDP offerer now removes the MSRP data channel with stream id 2, but SDP offerer 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 8. Security Considerations
No security considerations are envisaged beyond those already This document specifies new SDP attributes used in the negotiation of
documented in [RFC4566]. the DATA channel parameters.
8. IANA Considerations These parameter are negotiated as part of opening a SCTP channel over
8.1. Subprotocol Identifiers DTLS as specified in [I-D.ietf-mmusic-sctp-sdp]. This document do
not add any security considerations to the ones specified in the
above document
Error cases like the use of unknown parameter values or violation the
odd/even rule must be handled by closing the corresponding Data
Channel.
9. IANA Considerations
9.1. Subprotocol Identifiers
Registration of new subprotocol identifiers is performed using the Registration of new subprotocol identifiers is performed using the
existing IANA "WebSocket Subprotocol Name Registry" table. 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
skipping to change at page 21, line 31 skipping to change at page 22, line 37
"Subprotocol Definition" and "Reference" cells in the subprotocol's "Subprotocol Definition" and "Reference" cells in the subprotocol's
row of the IANA "WebSocket Subprotocol Name Registry" table should row of the IANA "WebSocket Subprotocol Name Registry" table should
contain two entries. One entry in each of these cells should refer contain two entries. One entry in each of these cells should refer
to the Websocket related subprotocol specification, and the other to the Websocket related subprotocol specification, and the other
entry should refer to the data channel related subprotocol entry should refer to the data channel related subprotocol
specification. specification.
NOTE to RFC Editor: Please replace "XXXX" with the number of this NOTE to RFC Editor: Please replace "XXXX" with the number of this
RFC. RFC.
8.2. New SDP Attributes 9.2. New SDP Attributes
8.2.1. dcmap 9.2.1. dcmap
NOTE to RFC Editor: Please replace "XXXX" with the number of this NOTE to RFC Editor: Please replace "XXXX" with the number of this
RFC. RFC.
This document defines a new SDP media-level attribute "a=dcmap:" as This document defines a new SDP media-level attribute "a=dcmap:" as
follows: follows:
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| Contact name: | MMUSIC Chairs | | Contact name: | MMUSIC Chairs |
| Contact email: | mmusic-chairs@ietf.org | | Contact email: | mmusic-chairs@ietf.org |
| Attribute name: | dcmap | | Attribute name: | dcmap |
| Attribute syntax: | As per Section 5.1.1.1 | | Attribute syntax: | As per Section 5.1.1.1 |
| Attribute semantics: | As per Section 5.1.1.1 | | Attribute semantics: | As per Section 5.1.1.1 |
| Usage level: | media | | Usage level: | media |
| Charset dependent: | No | | Charset dependent: | No |
| Purpose: | Define data channel specific parameters | | Purpose: | Define data channel specific parameters |
| Appropriate values: | As per Section 5.1.1.1 | | Appropriate values: | As per Section 5.1.1.1 |
| O/A procedures: | As per Section 5.2 | | O/A procedures: | As per Section 6 |
| Mux category: | SPECIAL. See Section 5.1.1.2 | | Mux category: | SPECIAL. See Section 5.1.1.2 |
| Reference: | RFCXXXX | | Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
8.2.2. dcsa 9.2.2. dcsa
NOTE to RFC Editor: Please replace "XXXX" with the number of this NOTE to RFC Editor: Please replace "XXXX" with the number of this
RFC. RFC.
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:
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| Contact name: | MMUSIC Chairs | | Contact name: | MMUSIC Chairs |
| Contact email: | mmusic-chairs@ietf.org | | Contact email: | mmusic-chairs@ietf.org |
| Attribute name: | dcsa | | Attribute name: | dcsa |
| Attribute syntax: | As per Section 5.1.2.1 | | Attribute syntax: | As per Section 5.1.2.1 |
| Attribute semantics: | As per Section 5.1.2.1 | | Attribute semantics: | As per Section 5.1.2.1 |
| Usage level: | media | | Usage level: | media |
| Charset dependent: | No | | Charset dependent: | No |
| Purpose: | Define data channel subprotocol specific | | Purpose: | Define data channel subprotocol specific |
| | attributes | | | attributes |
| Appropriate values: | As per Section 5.1.2.1 | | Appropriate values: | As per Section 5.1.2.1 |
| O/A procedures: | As per Section 5.2 | | O/A procedures: | As per Section 6 |
| Mux category: | SPECIAL. See Section 5.1.2.2 | | Mux category: | SPECIAL. See Section 5.1.2.2 |
| Reference: | RFCXXXX | | Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
8.3. New Usage Level 9.3. New Usage Level
This document introduces a new "Data Channel Subprotocol Attribute" This document introduces a new "Data Channel Subprotocol Attribute"
(dcsa) usage level to the SDP to the IANA SDP att-field registry. (dcsa) usage level of the SDP media description to the IANA SDP att-
SDP attributes that are defined for use at the dcsa usage level only field registry. SDP attributes that are defined for use at the dcsa
SHALL use the dcsa usage level when registering the attribute. If usage level only SHALL use the dcsa usage level when registering the
existing media attributes are used in a datachannel subprotocol attribute. If existing media attributes are used in a datachannel
specific way (Section 5.1.2.1), then a new dcsa usage level MUST be subprotocol specific way (Section 5.1.2.1), then a new dcsa usage
defined for the existing media attribute. Where the SDP attribute is level MUST be defined for the existing media attribute. Where the
applicable to a particular subprotocol/s this SHALL also be SDP attribute is applicable to a particular subprotocol/s this SHALL
registered by indicating the applicable subprotocol identifiers (see also be registered by indicating the applicable subprotocol
Section 8.1) along with the dcsa usage level. E.g. identifiers (see Section 9.1) along with the dcsa usage level. E.g.
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
| ... | ... | | ... | ... |
| Usage level: | dcsa(MSRP) | | Usage level: | dcsa(MSRP) |
| ... | ... | | ... | ... |
+-----------------------+-------------------------------------------+ +-----------------------+-------------------------------------------+
9. Acknowledgments 10. Acknowledgments
The authors wish to acknowledge the borrowing of ideas from other The authors wish to acknowledge the borrowing of ideas from other
internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley
and Gavin Llewellyn, and to thank Flemming Andreasen, Roni Even, and Gavin Llewellyn, and to thank Flemming Andreasen, Roni Even,
Christian Groves, Gunnar Hellstrom, Christer Holmberg, Paul Kyzivat, Christian Groves, Gunnar Hellstrom, Christer Holmberg, Paul Kyzivat,
Jonathan Lennox, Uwe Rauschenbach and Roman Shpount for their Jonathan Lennox, Uwe Rauschenbach and Roman Shpount for their
invaluable comments. invaluable comments.
10. CHANGE LOG 11. CHANGE LOG
10.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-14' 11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-15'
o Editorial changes separate sections for offer/answer procedures.
o Update security section.
11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-14'
o Change "dtls-id" to "tls-id" and assign 20 octet long values o Change "dtls-id" to "tls-id" and assign 20 octet long values
o Remove of RFC4566bis draft from list of normative references. o Remove of RFC4566bis draft from list of normative references.
10.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-12' 11.3. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-12'
o Modification of Keith's address information. o Modification of Keith's address information.
10.3. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-11' 11.4. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-11'
o dcmap-stream-id syntax change to limit size to 5 digits. o dcmap-stream-id syntax change to limit size to 5 digits.
o Add missing 'x' prefix to quoted-visible syntax. o Add missing 'x' prefix to quoted-visible syntax.
o Align SDP offerer and answerer handling when both max-retr and o Align SDP offerer and answerer handling when both max-retr and
max-time are present. max-time are present.
o Use of TEST-NET-1 ip addresses in examples. o Use of TEST-NET-1 ip addresses in examples.
o Add missing a=dtls-id in one example. o Add missing a=dtls-id in one example.
10.4. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-10' 11.5. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-10'
o Removal of the "a=connection" attribute lines from all SDP o Removal of the "a=connection" attribute lines from all SDP
examples. examples.
10.5. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-09' 11.6. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-09'
o In the introduction: o In the introduction:
* Replacement of the sentence "The RTCWeb working group has * Replacement of the sentence "The RTCWeb working group has
defined the concept of bi-directional data channels running on defined the concept of bi-directional data channels running on
top of SCTP/DTLS (SCTP over the Datagram Transport Layer top of SCTP/DTLS (SCTP over the Datagram Transport Layer
Security protocol)" with "The RTCWeb working group has defined Security protocol)" with "The RTCWeb working group has defined
the concept of bi-directional data channels running on top of the concept of bi-directional data channels running on top of
the Stream Control Transmission Protocol (SCTP)". the Stream Control Transmission Protocol (SCTP)".
skipping to change at page 24, line 38 skipping to change at page 25, line 40
values are not considered in this document." values are not considered in this document."
o Replacement of "DTLS connection" with "DTLS association" o Replacement of "DTLS connection" with "DTLS association"
throughout the document. throughout the document.
o In sections Section 5.1.1.2 and Section 5.1.2.2 removal of the o In sections Section 5.1.1.2 and Section 5.1.2.2 removal of the
sentences "This document also does not specify multiplexing rules sentences "This document also does not specify multiplexing rules
for this attribute for SCTP or SCTP/DTLS proto values". for this attribute for SCTP or SCTP/DTLS proto values".
o In the text related to "Subsequent SDP answer" in section o In the text related to "Subsequent SDP answer" in section
Section 5.2.5 replacement of "The DTLS/SCTP association remains Section 6.7 replacement of "The DTLS/SCTP association remains open
open ..." with "The SCTP association remains open ...". ..." with "The SCTP association remains open ...".
o In the text after the second SDP answer in section Section 6 o In the text after the second SDP answer in section Section 7
replacement of "... (after SCTP/DTLS association is setup)" with replacement of "... (after SCTP/DTLS association is setup)" with
"... (after the SCTP association is set up)". "... (after the SCTP association is set up)".
o Addition of [I-D.ietf-mmusic-dtls-sdp] to the list of informative o Addition of [I-D.ietf-mmusic-dtls-sdp] to the list of informative
references. references.
o Addition of "a=dtls-id" attribute lines to the SDP offer/answer o Addition of "a=dtls-id" attribute lines to the SDP offer/answer
examples in Section 6. examples in Section 7.
10.6. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-08' 11.7. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-08'
o Addition of definition of "data channel subprotocol" to Section 3 o Addition of definition of "data channel subprotocol" to Section 3
as proposed on the MMUSIC list, https://www.ietf.org/mail- as proposed on the MMUSIC list, https://www.ietf.org/mail-
archive/web/mmusic/current/msg15827.html. archive/web/mmusic/current/msg15827.html.
o Addition of RFC4566bis draft to list of normative references. o Addition of RFC4566bis draft to list of normative references.
o Updates of tables in Section 8.2.1 and Section 8.2.2 as per o Updates of tables in Section 9.2.1 and Section 9.2.2 as per
section 8.2.4 of RFC4566bis draft. section 8.2.4 of RFC4566bis draft.
o Addition of new Section 8.3. o Addition of new Section 9.3.
10.7. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-07' 11.8. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-07'
o Addition of two new paragraphs to Section 5.1.2.1 regarding o Addition of two new paragraphs to Section 5.1.2.1 regarding
subprotocol attribute relationship with transport protocol. subprotocol attribute relationship with transport protocol.
o Addition of a note to Section 8.1 regarding subprotocols o Addition of a note to Section 9.1 regarding subprotocols
simultaneously defined for data channel and Websocket usage. simultaneously defined for data channel and Websocket usage.
o Addition of two further SDP offer/answer considerations to o Addition of two further SDP offer/answer considerations to
Section 5.2.5 regarding unknown subprotocol attributes and known Section 6.7 regarding unknown subprotocol attributes and known
subprotocol attributes with unknown data channel transport related subprotocol attributes with unknown data channel transport related
semantic. semantic.
10.8. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-06' 11.9. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-06'
o Changes addressing Christian Groves's WGLC review comments raised o Changes addressing Christian Groves's WGLC review comments raised
in http://www.ietf.org/mail-archive/web/mmusic/current/ in http://www.ietf.org/mail-archive/web/mmusic/current/
msg15357.html and http://www.ietf.org/mail- msg15357.html and http://www.ietf.org/mail-
archive/web/mmusic/current/msg15359.html. archive/web/mmusic/current/msg15359.html.
10.9. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-05' 11.10. 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 9.2.1 and Section 9.2.2 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 subprotocol being transported ...". that this instance of the MSRP subprotocol being transported ...".
skipping to change at page 26, line 28 skipping to change at page 27, line 28
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".
10.10. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-04' 11.11. 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 9.1 specifies how new
subprotocol 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
normative references. normative references.
o Addition of dcmap attribute specific IANA registration o Addition of dcmap attribute specific IANA registration
Section 8.2.1. Section 9.2.1.
o Addition of dcsa attribute specific IANA registration o Addition of dcsa attribute specific IANA registration
Section 8.2.2. Section 9.2.2.
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.
10.11. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-03' 11.12. 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".
skipping to change at page 28, line 20 skipping to change at page 29, line 20
[I-D.ietf-rtcweb-data-protocol]" with "The intention in exchanging [I-D.ietf-rtcweb-data-protocol]" with "The intention in exchanging
these attributes is to create, on two peers, without use of DCEP these attributes is to create, on two peers, without use of DCEP
[I-D.ietf-rtcweb-data-protocol], matched pairs of oppositely [I-D.ietf-rtcweb-data-protocol], matched pairs of oppositely
directed data channels having the same set of attributes". directed data channels having the same set of attributes".
o In Section 5.1.1.6 replacement of "The 'max-retr' parameter o In Section 5.1.1.6 replacement of "The 'max-retr' parameter
indicates the maximal number a user message will be retransmitted" indicates the maximal number a user message will be retransmitted"
with "The 'max-retr' parameter indicates the maximal number of with "The 'max-retr' parameter indicates the maximal number of
times a user message will be retransmitted". times a user message will be retransmitted".
o In Section 5.2.1 replacement of "However, an SDP offer/answer o In Section 6.1 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 7 addition of the previously missing
colons to the "a=sctp-port" attribute lines. colons to the "a=sctp-port" attribute lines.
10.12. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02' 11.13. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02'
o Move of reference draft-ietf-rtcweb-jsep from the list of o Move of reference draft-ietf-rtcweb-jsep from the list of
normative references to the list of informative references. normative references to the list of informative references.
Remover in -07 since not referenced Remover in -07 since not referenced
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
skipping to change at page 29, line 16 skipping to change at page 30, line 16
"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
terms. terms.
o In Section 5.2.1 replacement of sentence "However, a single stream o In Section 6.1 replacement of sentence "However, a single stream
is managed using one method at a time." with "However, an SDP is managed using one method at a time." with "However, an SDP
offer/answer exchange MUST NOT be initiated if the associated SCTP offer/answer exchange MUST NOT be initiated if the associated SCTP
stream is already negotiated via DCEP". stream is already negotiated via DCEP".
o In Section 5.2.2 replacement of sentence "By definition max-retr o In Section 6.2 replacement of sentence "By definition max-retr and
and max-time are mutually exclusive, so only one of them can be max-time are mutually exclusive, so only one of them can be
present in a=dcmap" with "By definition max-retr and max-time are present in a=dcmap" with "By definition max-retr and max-time are
mutually exclusive, so at most one of them MAY be present in mutually exclusive, so at most one of them MAY be present in
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.
10.13. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01' 11.14. 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 9.1 "Subprotocol identifiers" as
subsection of the "IANA Considerations" related Section 8. Also subsection of the "IANA Considerations" related Section 9. Also
removal of the temporary note "To be completed. As [I-D.ietf- removal of the temporary note "To be completed. As [I-D.ietf-
rtcweb-data-protocol] this document should refer to IANA's rtcweb-data-protocol] this document should refer to IANA's
WebSocket Subprotocol Name Registry defined in [RFC6455]" WebSocket Subprotocol Name Registry defined in [RFC6455]"
o In Section 5.2.2: o In Section 6.2:
* In the first paragraph replacement of the sentence "If an SDP * In the first paragraph replacement of the sentence "If an SDP
offer contains both of these parameters then such an SDP offer offer contains both of these parameters then such an SDP offer
will be rejected." with "If an SDP offer contains both of these will be rejected." with "If an SDP offer contains both of these
parameters then the receiver of such an SDP offer MUST reject parameters then the receiver of such an SDP offer MUST reject
the SDP offer." the SDP offer."
* In the second paragraph capitalization of "shall" and "may" * In the second paragraph capitalization of "shall" and "may"
such that both sentences now read: "The SDP answer SHALL echo such that both sentences now read: "The SDP answer SHALL echo
the same subprotocol, max-retr, max-time, ordered parameters, the same subprotocol, max-retr, max-time, ordered parameters,
skipping to change at page 30, line 20 skipping to change at page 31, line 20
different from the SDP offer, in the SDP answer." different from the SDP offer, in the SDP answer."
* In the third paragraph replacement of the sentence "The same * In the third paragraph replacement of the sentence "The same
information MUST be replicated without changes in any information MUST be replicated without changes in any
subsequent offer or answer, as long as the data channel is subsequent offer or answer, as long as the data channel is
still opened at the time of offer or answer generation." with still opened at the time of offer or answer generation." with
"When sending a subsequent offer or an answer, and for as long "When sending a subsequent offer or an answer, and for as long
as the data channel is still open, the sender MUST replicate as the data channel is still open, the sender MUST replicate
the same information.". the same information.".
o In Section 5.2.2 the mapping of data channel types defined in o In Section 6.2 the mapping of data channel types defined in
[I-D.ietf-rtcweb-data-protocol] to the SDP "a=dcmap" attribute [I-D.ietf-rtcweb-data-protocol] to the SDP "a=dcmap" attribute
parameters were illustrated using example "a=dcmap" attribute parameters were illustrated using example "a=dcmap" attribute
lines. Replacement of these example "a=dcmap" attribute lines lines. Replacement of these example "a=dcmap" attribute lines
with just the "a=dcmap" attribute parameters being relevant for with just the "a=dcmap" attribute parameters being relevant for
the channel type. the channel type.
o In Section 5.2.5 the description of bullet point "SDP offer has no o In Section 6.7 the description of bullet point "SDP offer has no
a=dcmap attributes - Initial SDP offer:" was "Initial SDP offer: a=dcmap attributes - Initial SDP offer:" was "Initial SDP offer:
No data channel negotiated yet." Replacement of this description No data channel negotiated yet." Replacement of this description
with "Initial SDP offer: No data channel is negotiated yet. The with "Initial SDP offer: No data channel is negotiated yet. The
DTLS connection and SCTP association is negotiated and, if agreed, DTLS 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]."
o In Section 5.2.5 in both bullet points related to "Subsequent SDP o In Section 6.7 in both bullet points related to "Subsequent SDP
offer" and "Subsequent SDP answer" replacement of "All the offer" and "Subsequent SDP answer" replacement of "All the
externally negotiated data channels must be closed now." with "All externally negotiated data channels must be closed now." with "All
the externally negotiated data channels are expected to be closed the externally negotiated data channels are expected to be closed
now.". now.".
o In Appendix A.2.2's sixth paragraph beginning with "[ASSUMPTION]" o In Appendix A.2.2's sixth paragraph beginning with "[ASSUMPTION]"
replacement of the two occurrences of "must" with "MUST". replacement of the two occurrences of "must" with "MUST".
o In Section 5.1.1.1 in the definition of the ABNF rule "dcmap-opt" o In Section 5.1.1.1 in the definition of the ABNF rule "dcmap-opt"
there was a comment saying that "Either only maxretr-opt or there was a comment saying that "Either only maxretr-opt or
skipping to change at page 31, line 13 skipping to change at page 32, line 13
NOT be present." NOT be present."
o In Section 5.1.1.8 replacement of the first sentence "The o In Section 5.1.1.8 replacement of the first sentence "The
'ordered' parameter with value "true" indicates that DATA chunks 'ordered' parameter with value "true" indicates that DATA chunks
in the channel MUST be dispatched to the upper layer by the in the channel MUST be dispatched to the upper layer by the
receiver while preserving the order." with "The 'ordered' receiver while preserving the order." with "The 'ordered'
parameter with value "true" indicates that the receiver MUST parameter with value "true" indicates that the receiver MUST
dispatch DATA chunks in the data channel to the upper layer while dispatch DATA chunks in the data channel to the upper layer while
preserving the order.". preserving the order.".
o In Section 5.2.3's first paragraph replacement of the one o In Section 6.3's first paragraph replacement of the one occurrence
occurrence of "must" with "..., it MUST wait until ...". of "must" with "..., it MUST wait until ...".
o In Section 5.2.4: o In Section 6.6:
* In the second paragraph replacement of "must" with "... whether * In the second paragraph replacement of "must" with "... whether
this closing MUST in addition ..." this closing MUST in addition ..."
* In the third paragraph replacement of the sentence "The port * In the third paragraph replacement of the sentence "The port
value for the "m" line SHOULD NOT be changed (e.g., to zero) value for the "m" line SHOULD NOT be changed (e.g., to zero)
when closing a data channel ..." with "The offerer SHOULD NOT when closing a data channel ..." with "The offerer SHOULD NOT
change the port value for the "m" line (e.g., to zero) when change the port value for the "m" line (e.g., to zero) when
closing a data channel ...". closing a data channel ...".
skipping to change at page 31, line 42 skipping to change at page 32, line 42
* 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."
10.14. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00' 11.15. 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 33, line 5 skipping to change at page 34, line 5
rule with name "escaped" was defined. Renamed that rule's name to rule with name "escaped" was defined. Renamed that rule's name to
"escaped-char". "escaped-char".
o Insertion of a dedicated note right after the "a=dcmap:4" o Insertion of a dedicated note right after the "a=dcmap:4"
attribute example in Section 5.1.1.1 regarding the non-printable attribute example in Section 5.1.1.1 regarding the non-printable
"escaped-char" character within the "label" value. "escaped-char" character within the "label" value.
o In Section 5.1.2's second paragraph replacement of "sctp stream o In Section 5.1.2's second paragraph replacement of "sctp stream
identifier" with "SCTP stream identifier". identifier" with "SCTP stream identifier".
o In first paragraph of Section 5.2.1 replacement of first two o In first paragraph of Section 6.1 replacement of first two
sentences 'For the SDP-based external negotiation described in sentences 'For the SDP-based external negotiation described in
this document, the initial offerer based "SCTP over DTLS" owns by this document, the initial offerer based "SCTP over DTLS" owns by
convention the even stream identifiers whereas the initial convention the even stream identifiers whereas the initial
answerer owns the odd stream identifiers. This ownership is answerer owns the odd stream identifiers. This ownership is
invariant for the whole lifetime of the signaling session, e.g. it invariant for the whole lifetime of the signaling session, e.g. it
does not change if the initial answerer sends a new offer to the does not change if the initial answerer sends a new offer to the
initial offerer.' with 'If an SDP offer/answer exchange (could be initial offerer.' with 'If an SDP offer/answer exchange (could be
the initial or a subsequent one) results in a UDP/DTLS/SCTP or the initial or a subsequent one) results in a UDP/DTLS/SCTP or
TCP/DTLS/SCTP based media description being accepted, and if this TCP/DTLS/SCTP based media description being accepted, and if this
SDP offer/answer exchange results in the establishment of a new SDP offer/answer exchange results in the establishment of a new
SCTP association, then the SDP offerer owns the even SCTP stream SCTP association, then the SDP offerer owns the even SCTP stream
ids of this new SCTP association and the answerer owns the odd ids of this new SCTP association and the answerer owns the odd
SCTP stream identifiers. If this "m" line is removed from the SCTP stream identifiers. If this "m" line is removed from the
signaling session (its port number set to zero), and if usage of signaling session (its port number set to zero), and if usage of
this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is
renegotiated later on, then the even and odd SCTP stream renegotiated later on, then the even and odd SCTP stream
identifier ownership is redetermined as well as described above.' identifier ownership is redetermined as well as described above.'
o In Section 5.2.3 the first action of an SDP answerer, when o In Section 6.3 the first action of an SDP answerer, when receiving
receiving an SDP offer, was described as "Applies the SDP offer. an SDP offer, was described as "Applies the SDP offer. Note that
Note that the browser ignores data channel specific attributes in the browser ignores data channel specific attributes in the SDP."
the SDP." Replacement of these two sentences with "Parses and Replacement of these two sentences with "Parses and applies the
applies the SDP offer. Note that the typical parser normally SDP offer. Note that the typical parser normally ignores unknown
ignores unknown SDP attributes, which includes data channel SDP attributes, which includes data channel related attributes."
related attributes."
o In Section 5.2.3 the second sentence of the third SDP answerer o In Section 6.3 the second sentence of the third SDP answerer
action was "Note that the browser is asked to create data channels action was "Note that the browser is asked to create data channels
with stream identifiers not "owned" by the agent.". Replacement with stream identifiers not "owned" by the agent.". Replacement
of this sentence with "Note that the agent is asked to create data of this sentence with "Note that the agent is asked to create data
channels with SCTP stream identifiers contained in the SDP offer channels with SCTP stream identifiers contained in the SDP offer
if the SDP offer is accepted." if the SDP offer is accepted."
o In Section 5.2.4 the third paragraph began with "A data channel o In Section 6.6 the third paragraph began with "A data channel can
can be closed by sending a new SDP offer which excludes the dcmap be closed by sending a new SDP offer which excludes the dcmap and
and dcsa attribute lines for the data channel. The port value for dcsa attribute lines for the data channel. The port value for the
the m line SHOULD NOT be changed (e.g., to zero) when closing a m line SHOULD NOT be changed (e.g., to zero) when closing a data
data channel (unless all data channels are being closed and the channel (unless all data channels are being closed and the SCTP
SCTP association is no longer needed), since this would close the association is no longer needed), since this would close the SCTP
SCTP association and impact all of the data channels. If the association and impact all of the data channels. If the answerer
answerer accepts the SDP offer then it MUST also exclude the accepts the SDP offer then it MUST also exclude the corresponding
corresponding attribute lines in the answer. ..." Replacement of attribute lines in the answer. ..." Replacement of this part with
this part with "The intention to close a data channel can be "The intention to close a data channel can be signaled by sending
signaled by sending a new SDP offer which excludes the "a=dcmap:" a new SDP offer which excludes the "a=dcmap:" and "a=dcsa:"
and "a=dcsa:" attribute lines for the data channel. The port attribute lines for the data channel. The port value for the "m"
value for the "m" line SHOULD NOT be changed (e.g., to zero) when line SHOULD NOT be changed (e.g., to zero) when closing a data
closing a data channel (unless all data channels are being closed channel (unless all data channels are being closed and the SCTP
and the SCTP association is no longer needed), since this would association is no longer needed), since this would close the SCTP
close the SCTP association and impact all of the data channels. association and impact all of the data channels. If the answerer
If the answerer accepts the SDP offer then it MUST close those accepts the SDP offer then it MUST close those data channels whose
data channels whose "a=dcmap:" and "a=dcsa:" attribute lines were "a=dcmap:" and "a=dcsa:" attribute lines were excluded from the
excluded from the received SDP offer, unless those data channels received SDP offer, unless those data channels were already
were already closed, and it MUST also exclude the corresponding closed, and it MUST also exclude the corresponding attribute lines
attribute lines in the answer." in the answer."
o In Section 5.2.4 the hanging text after the third paragraph was o In Section 6.6 the hanging text after the third paragraph was
"This delayed close is to handle cases where a successful SDP "This delayed close is to handle cases where a successful SDP
answer is not received, in which case the state of session should answer is not received, in which case the state of session should
be kept per the last successful SDP offer/answer." Replacement of be kept per the last successful SDP offer/answer." Replacement of
this sentence with "This delayed closure is RECOMMENDED in order this sentence with "This delayed closure is RECOMMENDED in order
to handle cases where a successful SDP answer is not received, in to handle cases where a successful SDP answer is not received, in
which case the state of the session SHOULD be kept per the last which case the state of the session SHOULD be kept per the last
successful SDP offer/answer." successful SDP offer/answer."
o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects
Section 5.1.1 contained already procedural descriptions related to Section 5.1.1 contained already procedural descriptions related to
data channel reliability negotiation. Creation of new data channel reliability negotiation. Creation of new Section 6.2
Section 5.2.2 and moval of reliability negotiation related text to and moval of reliability negotiation related text to this new
this new section. section.
10.15. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02' 11.16. 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 35, line 30 skipping to change at page 36, line 28
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.
10.16. Changes against '-01' 11.17. 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.
10.17. Changes against '-00' 11.18. Changes against '-00'
o Revisions to identify difference between internal and external o Revisions to identify difference between internal and external
negotiation and their usage. negotiation and their usage.
o Introduction of more generic terminology, e.g. "application" o Introduction of more generic terminology, e.g. "application"
instead of "browser". instead of "browser".
o Clarification of how "max-retr and max-time affect the usage of o Clarification of how "max-retr and max-time affect the usage of
unreliable and reliable WebRTC data channels. unreliable and reliable WebRTC data channels.
o Updates of examples to take into account the SDP syntax changes o Updates of examples to take into account the SDP syntax changes
introduced with draft-ietf-mmusic-sctp-sdp-07. introduced with draft-ietf-mmusic-sctp-sdp-07.
o Removal of the SCTP port number from the a=dcmap and a=dcsa o Removal of the SCTP port number from the a=dcmap and a=dcsa
attributes as this is now contained in the a=sctp-port attribute, attributes as this is now contained in the a=sctp-port attribute,
and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP
association on top of the DTLS connection. association on top of the DTLS connection.
11. References 12. References
11.1. Normative References 12.1. Normative References
[I-D.ietf-mmusic-sctp-sdp] [I-D.ietf-mmusic-sctp-sdp]
Holmberg, C., Shpount, R., Loreto, S., and G. Camarillo, Holmberg, C., Shpount, R., Loreto, S., and G. Camarillo,
"Session Description Protocol (SDP) Offer/Answer "Session Description Protocol (SDP) Offer/Answer
Procedures For Stream Control Transmission Protocol (SCTP) Procedures For Stream Control Transmission Protocol (SCTP)
over Datagram Transport Layer Security (DTLS) Transport.", over Datagram Transport Layer Security (DTLS) Transport.",
draft-ietf-mmusic-sctp-sdp-26 (work in progress), April draft-ietf-mmusic-sctp-sdp-26 (work in progress), April
2017. 2017.
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
skipping to change at page 37, line 5 skipping to change at page 38, line 5
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>. July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>. <https://www.rfc-editor.org/info/rfc5234>.
11.2. Informative References 12.2. Informative References
[I-D.ietf-clue-datachannel]
Holmberg, C., "CLUE Protocol data channel", draft-ietf-
clue-datachannel-14 (work in progress), August 2016.
[I-D.ietf-mmusic-dtls-sdp] [I-D.ietf-mmusic-dtls-sdp]
Holmberg, C. and R. Shpount, "Session Description Protocol Holmberg, C. and R. Shpount, "Session Description Protocol
(SDP) Offer/Answer Considerations for Datagram Transport (SDP) Offer/Answer Considerations for Datagram Transport
Layer Security (DTLS) and Transport Layer Security (TLS)", Layer Security (DTLS) and Transport Layer Security (TLS)",
draft-ietf-mmusic-dtls-sdp-32 (work in progress), October draft-ietf-mmusic-dtls-sdp-32 (work in progress), October
2017. 2017.
[I-D.ietf-mmusic-msrp-usage-data-channel]
Drage, K., Makaraju, M., Stoetzer-Bradler, J., Ejzak, R.,
and J. Marcon, "MSRP over Data Channels", draft-ietf-
mmusic-msrp-usage-data-channel-07 (work in progress),
September 2017.
[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.
[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/
skipping to change at page 38, line 48 skipping to change at page 40, line 13
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.
Note:For data channels negotiated with the DCEP, one endpoint owns Note:For data channels negotiated with the DCEP, one endpoint owns
by convention the even stream identifiers, whereas the other owns by convention the even stream identifiers, whereas the other owns
the odd stream identifiers, as defined in the odd stream identifiers, as defined in
[I-D.ietf-rtcweb-data-protocol]. [I-D.ietf-rtcweb-data-protocol].
Note:For data channels negotiated via some protocol different from Note:For data channels negotiated via different protocol 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 transport parameters and does not provide for negotiation of
subprotocol specific parameters. DCEP-less data channel negotiation subprotocol specific parameters. DCEP-less data channel negotiation
can be defined to allow negotiation of parameters beyond those can be defined to allow negotiation of parameters beyond those
 End of changes. 101 change blocks. 
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