draft-ietf-mmusic-data-channel-sdpneg-02.txt		draft-ietf-mmusic-data-channel-sdpneg-03.txt
	MMUSIC K. Drage, Ed.		MMUSIC K. Drage, Ed.
	Internet-Draft M. Makaraju		Internet-Draft M. Makaraju
	Intended status: Standards Track J. Stoetzer-Bradler		Intended status: Standards Track J. Stoetzer-Bradler
	Expires: October 12, 2015 Alcatel-Lucent		Expires: January 22, 2016 Alcatel-Lucent
	R. Ejzak		R. Ejzak
	J. Marcon		J. Marcon
	Unaffiliated		Unaffiliated
	April 10, 2015		July 21, 2015
	SDP-based Data Channel Negotiation		SDP-based Data Channel Negotiation
	draft-ietf-mmusic-data-channel-sdpneg-02		draft-ietf-mmusic-data-channel-sdpneg-03
	Abstract		Abstract
	The Real-Time Communication in WEB-browsers (RTCWeb) working group is		The Real-Time Communication in WEB-browsers (RTCWeb) working group is
	charged to provide protocols to support direct interactive rich		charged to provide protocols to support direct interactive rich
	communications using audio, video, and data between two peers' web-		communications using audio, video, and data between two peers' web-
	browsers. For the support of data communication, the RTCWeb working		browsers. For the support of data communication, the RTCWeb working
	group has in particular defined the concept of bi-directional data		group has in particular defined the concept of bi-directional data
	channels over SCTP, where each data channel might be used to		channels over SCTP, where each data channel might be used to
	transport other protocols, called sub-protocols. Data channel setup		transport other protocols, called sub-protocols. Data channel setup
	can be done using either the internal in-band band (also referred to		can be done using either the in-band Data Channel Establishment
	as 'internal' for the rest of the document) Data Channel		Protocol (DCEP) or using some out-of-band non-DCEP protocol. This
	Establishment Protocol or some external out-of-band simply referred
	to as 'external negotiation' in the rest of the document . This
	document specifies how the SDP offer/answer exchange can be used to		document specifies how the SDP offer/answer exchange can be used to
	achieve such an external negotiation. Even though data channels are		achieve such an out-of-band non-DCEP negotiation. Even though data
	designed for RTCWeb use initially they may be used by other protocols		channels are designed for RTCWeb use initially they may be used by
	like, but not limited to, the CLUE protocol. This document is		other protocols like, but not limited to, the CLUE protocol. This
	intended to be used wherever data channels are used.		document is intended to be used wherever data channels are used.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on October 12, 2015.		This Internet-Draft will expire on January 22, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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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 . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
	4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4		4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
	5. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 5		5. Data Channels . . . . . . . . . . . . . . . . . . . . . . . . 5
	5.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5		5.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 5
	5.2. Generic External Negotiation . . . . . . . . . . . . . . 6		5.2. Generic Non-DCEP Negotiation . . . . . . . . . . . . . . 6
	5.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6		5.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 6
	5.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6		5.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 6
	5.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 7		5.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 8
	6. SDP-based External Negotiation . . . . . . . . . . . . . . . 8		6. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 8
	6.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 8		6.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 9
	6.1.1. SDP Attribute for Data Channel Parameter Negotiation 8		6.1.1. SDP Attribute for Data Channel Parameter Negotiation 9
	6.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 8		6.1.1.1. dcmap Attribute . . . . . . . . . . . . . . . . . 9
	6.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 10		6.1.1.2. dcmap-stream-id Parameter . . . . . . . . . . . . 11
	6.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 10		6.1.1.3. label Parameter . . . . . . . . . . . . . . . . . 11
	6.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 10		6.1.1.4. subprotocol Parameter . . . . . . . . . . . . . . 11
	6.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 10		6.1.1.5. max-retr Parameter . . . . . . . . . . . . . . . 11
	6.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 11		6.1.1.6. max-time Parameter . . . . . . . . . . . . . . . 12
	6.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 11		6.1.1.7. ordered Parameter . . . . . . . . . . . . . . . . 12
	6.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 11		6.1.2. Sub-Protocol Specific Attributes . . . . . . . . . . 12
	6.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12		6.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 14
	6.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 13		6.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 14
	6.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13		6.2.2. Negotiating Data Channel Parameters . . . . . . . . . 14
	6.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14		6.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 15
	6.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16		6.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 17
	6.2.5. Various SDP Offer/Answer Scenarios and Considerations 17		6.2.5. Various SDP Offer/Answer Scenarios and Considerations 18
	7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18		7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 19
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 20		8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
	9.1. Subprotocol identifiers . . . . . . . . . . . . . . . . . 20		9.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 21
			9.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 22
	10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21		9.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 22
	11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 21		9.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 22
			10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
			11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 22
	11.1. Changes against 'draft-ietf-mmusic-data-channel-		11.1. Changes against 'draft-ietf-mmusic-data-channel-
	sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 21		sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 22
	11.2. Changes against 'draft-ietf-mmusic-data-channel-		11.2. Changes against 'draft-ietf-mmusic-data-channel-
	sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 23		sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 23
	11.3. Changes against 'draft-ejzak-mmusic-data-channel-		11.3. Changes against 'draft-ietf-mmusic-data-channel-
	sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 26		sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 25
	11.4. Changes against '-01' . . . . . . . . . . . . . . . . . 27		11.4. Changes against 'draft-ejzak-mmusic-data-channel-
	11.5. Changes against '-00' . . . . . . . . . . . . . . . . . 27		sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 28
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . 28		11.5. Changes against '-01' . . . . . . . . . . . . . . . . . 29
	12.1. Normative References . . . . . . . . . . . . . . . . . . 28		11.6. Changes against '-00' . . . . . . . . . . . . . . . . . 29
	12.2. Informative References . . . . . . . . . . . . . . . . . 28		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29		12.1. Normative References . . . . . . . . . . . . . . . . . . 30
			12.2. Informative References . . . . . . . . . . . . . . . . . 31
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
	1. Introduction		1. Introduction
	The RTCWeb working group has defined the concept of bi-directional		The RTCWeb working group has defined the concept of bi-directional
	data channels running on top of SCTP/DTLS. RTCWeb leaves it open for		data channels running on top of SCTP/DTLS. RTCWeb leaves it open for
	other applications to use data channels and its in-band or out-of-		other applications to use data channels and its in-band DCEP or out-
	band protocol for creating them. Each data channel consists of		of-band non-DCEP protocols for creating them. Each data channel
	paired SCTP streams sharing the same SCTP Stream Identifier. Data		consists of paired SCTP streams sharing the same SCTP Stream
	channels are created by endpoint applications through the WebRTC API,		Identifier. Data channels are created by endpoint applications
	or other users of data channel like CLUE, and can be used to		through the WebRTC API, or other users of data channel like CLUE, and
	transport proprietary or well-defined protocols, which in the latter		can be used to transport proprietary or well-defined protocols, which
	case can be signaled by the data channel "sub-protocol" parameter,		in the latter case can be signaled by the data channel "sub-protocol"
	conceptually similar to the WebSocket "sub-protocol". However, apart		parameter, conceptually similar to the WebSocket "sub-protocol".
	from the "sub-protocol" value transmitted to the peer, RTCWeb leaves		However, apart from the "sub-protocol" value transmitted to the peer,
	it open how endpoint applications can agree on how to instantiate a		RTCWeb leaves it open how endpoint applications can agree on how to
	given sub-protocol on a data channel, and whether it is signaled in-		instantiate a given sub-protocol on a data channel, and whether it is
	band or out-of-band (or both). In particular, the SDP offer		signaled in-band using DCEP or out-of-band using a non-DCEP protocol
	generated by the application includes no channel-specific		(or both). In particular, the SDP offer generated by the application
	information.		includes no channel-specific information.
	This document defines SDP-based out-of-band negotiation procedures to		This document defines SDP offer/answer negotiation procedures to
	establish data channels for transport of well-defined sub-protocols.		establish data channels for transport of well-defined sub-protocols,
			to enable out-of-band negotiation.
	2. Conventions		2. Conventions
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	3. Terminology		3. Terminology
	This document uses the following terms:		This document uses the following terms:
	Data channel: A WebRTC data channel as specified in		Data channel: A WebRTC data channel as specified in
	[I-D.ietf-rtcweb-data-channel].		[I-D.ietf-rtcweb-data-channel].
	Data channel stack: An entity which, upon application request,		Data channel stack: An entity which, upon application request,
	runs data channel protocol to keep track of states, sending and		runs the data channel protocol to keep track of states, sending
	receive data. If the application is browser based JavaScript		and receive data. If the application is a browser based
	application then this stack resides in the browser. If the		JavaScript application then this stack resides in the browser. If
	application is a native application then this stack resides in		the application is a native application then this stack resides in
	application and accessible to it via some sort of APIs.		the application and is accessible via some sort of APIs.
	Data channel properties: fixed properties assigned to a data		Data channel properties: Fixed properties assigned to a data
	channel at the time of its creation. Some of these properties		channel at the time of its creation. Some of these properties
	determine the way the data channel stack transmits data on this		determine the way the data channel stack transmits data on this
	channel (e.g., stream identifier, reliability, order of		channel (e.g., stream identifier, reliability, order of
	delivery...).		delivery...).
	DCEP - Data Channel Establishment Protocol defined in		DCEP: Data Channel Establishment Protocol defined in
	[I-D.ietf-rtcweb-data-protocol].
	External negotiation: Data channel negotiation based on SDP offer/
	answer outlined in this specification.
	Internal negotiation: Data channel negotiation based on the Data
	Channel Establishment Protocol defined in
	[I-D.ietf-rtcweb-data-protocol].		[I-D.ietf-rtcweb-data-protocol].
	In-band: transmission through the peer-to-peer SCTP association.		In-band: Transmission through the peer-to-peer SCTP association.
	In-band negotiation: data channel negotiation based on the Data
	Channel Establishment Protocol defined in
	[I-D.ietf-rtcweb-data-protocol].
	Out-of-band: transmission through the application signaling path.		Out-of-band: Transmission through the application signaling path.
	Peer: From the perspective of one of the agents in a session, its		Peer: From the perspective of one of the agents in a session, its
	peer is the other agent. Specifically, from the perspective of		peer is the other agent. Specifically, from the perspective of
	the SDP offerer, the peer is the SDP answerer. From the		the SDP offerer, the peer is the SDP answerer. From the
	perspective of the SDP answerer, the peer is the SDP offerer.		perspective of the SDP answerer, the peer is the SDP offerer.
	Stream identifier: the identifier of the outbound and inbound SCTP		SCTP Stream Sequence Number (SSN): the SCTP stream sequence number
			as specified in [RFC4960].
			Stream identifier: The identifier of the outbound and inbound SCTP
	streams composing a data channel.		streams composing a data channel.
	4. Applicability Statement		4. Applicability Statement
	The mechanism in this specification only applies to the Session		The mechanism in this specification only applies to the Session
	Description Protocol (SDP) [RFC4566], when used together with the SDP		Description Protocol (SDP) [RFC4566], when used together with the SDP
	offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of		offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of
	scope of this document, and is thus undefined.		scope of this document, and is thus undefined.
	5. Data Channels		5. Data Channels
	This section summarizes how data channels work in general. Note that		This section summarizes how data channels work in general.
	the references to 'browser' here is intentional as in this specific
	example the data channel user is a Webrtc enabled browser.
	A WebRTC application creates a data channel via the data channel API,		A WebRTC application creates a data channel by providing a number of
	by providing a number of setup parameters (sub-protocol, label,		setup parameters (sub-protocol, label, reliability, order of
	reliability, order of delivery, priority). The application also		delivery, priority). The application also specifies if it wants to
	specifies if it wants to make use of the in-band negotiation using		make use of the negotiation using the DCEP
	the DCEP [I-D.ietf-rtcweb-data-protocol], or if the application		[I-D.ietf-rtcweb-data-protocol], or if the application intends to
	intends to perform an "external negotiation" using some other in-band		negotiate data channels using the SDP offer/answer protocol.
	or out-of-band mechanism.
	In any case, the SDP offer generated by the browser is per		In any case, the SDP offer generated by the browser is per
	[I-D.ietf-mmusic-sctp-sdp]. In brief, it contains one "m" line for		[I-D.ietf-mmusic-sctp-sdp]. In brief, it contains one "m" line for
	the SCTP association on top of which data channels will run, and one		the SCTP association on top of which data channels will run:
	attribute per protocol assigned to the SCTP ports:
	m=application 54111 UDP/DTLS/SCTP webrtc-datachannel		m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
	c=IN IP4 79.97.215.79		c=IN IP4 79.97.215.79
	a=max-message-size:100000		a=max-message-size:100000
	a=sctp-port 5000		a=sctp-port 5000
	a=setup:actpass		a=setup:actpass
	a=connection:new		a=connection:new
	a=fingerprint:SHA-1 \		a=fingerprint:SHA-1 \
	4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB		4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
	Note: A WebRTC browser will only use "m" line format "webrtc-		Note: A WebRTC browser will only use "m" line format "webrtc-
	datachannel", and will not use other formats in the "m" line for		datachannel", and will not use other formats in the "m" line for
	other protocols such as t38. [I-D.ietf-mmusic-sctp-sdp] supports		other protocols such as t38. [I-D.ietf-mmusic-sctp-sdp] supports
	only one SCTP association to be established on top of a DTLS session.		only one SCTP association to be established on top of a DTLS session.
	Note: This SDP syntax does not contain any channel-specific		Note: This SDP syntax does not contain any channel-specific
	information.		information.
	5.1. Stream Identifier Numbering		5.1. Stream Identifier Numbering
			[Editor's note: This entire Section 5.1 could possibly be removed as
			there is another section (Section 6.2.1) which is dedicated to SCTP
			stream id usage.]
	Independently from the requested type of negotiation, the application		Independently from the requested type of negotiation, the application
	creating a data channel can either pass to the browser the stream		creating a data channel can either pass to the browser the stream
	identifier to assign to the data channel or else let the browser pick		identifier to assign to the data channel or else let the browser pick
	one identifier from the ones unused.		one identifier from the ones unused.
	To avoid glare situations, each endpoint can moreover own an		To avoid glare situations, each endpoint can moreover own an
	exclusive set of stream identifiers, in which case an endpoint can		exclusive set of stream identifiers, in which case an endpoint can
	only create a data channel with a stream identifier it owns.		only create a data channel with a stream identifier it owns.
	Which set of stream identifiers is owned by which endpoint is		Which set of stream identifiers is owned by which endpoint is
	determined by convention or other means.		determined by convention or other means.
	For data channels negotiated in-band, one endpoint owns by		For data channels negotiated with the DCEP, one endpoint owns by
	convention the even stream identifiers, whereas the other owns the		convention the even stream identifiers, whereas the other owns the
	odd stream identifiers, as defined in		odd stream identifiers, as defined in
	[I-D.ietf-rtcweb-data-protocol].		[I-D.ietf-rtcweb-data-protocol].
	For data channels externally negotiated, no convention is defined		For data channels negotiated via some non-DCEP protocol, no
	by default.		convention is defined by default.
	5.2. Generic External Negotiation		5.2. Generic Non-DCEP Negotiation
			[Editor's note: As this document now focuses on SDP offer/answer
			negotiation only, should this entire Section 5.2 (and all its sub-
			sections) be removed? Parts of the information provided in these
			sub-sections might be moved to Section 6, Section 6.2.1 and
			Section 6.2.3 as indicated below in further editor notes. Another
			option might be to move this section and its sub-section to an
			informative appendix.]
	5.2.1. Overview		5.2.1. Overview
	In-band negotiation only provides for negotiation of data channel		DCEP negotiation only provides for negotiation of data channel
	transport parameters and does not provide for negotiation of sub-		transport parameters and does not provide for negotiation of sub-
	protocol specific parameters. External negotiation can be defined to		protocol specific parameters. Non-DCEP negotiation can be defined to
	allow negotiation of parameters beyond those handled by in-band		allow negotiation of parameters beyond those handled by DCEP
	negotiation, e.g., parameters specific to the sub-protocol		negotiation, e.g., parameters specific to the sub-protocol
	instantiated on a particular data channel. See Section 6.1.2 for an		instantiated on a particular data channel. See Section 6.1.2 for an
	example of such a parameter.		example of such a parameter.
	The following procedures are common to all methods of external		[Editor's note: The information in the preceding paragraph might be
			moved to Section 6.]
			The following procedures are common to all methods of non-DCEP
	negotiation, whether in-band (communicated using proprietary means on		negotiation, whether in-band (communicated using proprietary means on
	an already established data channel) or out-of-band (using SDP or		an already established data channel) or out-of-band (using SDP offer/
	some other protocol associated with the signaling channel).		answer or some other protocol associated with the signaling channel).
			[Editor's note: The preceding paragraph could be deleted.]
	5.2.2. Opening a Data Channel		5.2.2. Opening a Data Channel
	In the case of external negotiation, the endpoint application has the		In the case of non-DCEP negotiation, the endpoint application has the
	option to fully control the stream identifier assignments. However		option to fully control the stream identifier assignments. However
	these assignments have to coexist with the assignments controlled by		these assignments have to coexist with the assignments controlled by
	the data channel stack for the in-band negotiated data channels (if		the data channel stack for the DCEP negotiated data channels (if
	any). It is the responsibility of the application to ensure		any). It is the responsibility of the application to ensure
	consistent assignment of stream identifiers.		consistent assignment of stream identifiers.
			[Editor's note: The information in the preceding paragraph could be
			moved to Section 6.2.1.]
	When the application requests the creation of a new data channel to		When the application requests the creation of a new data channel to
	be set up via external negotiation, the data channel stack creates		be set up via non-DCEP negotiation, the data channel stack creates
	the data channel locally without sending any DATA_CHANNEL_OPEN		the data channel locally without sending any DATA_CHANNEL_OPEN
	message in-band, and sets the data channel state to Connecting if the		message in-band [Editor's note: The information in this first part of
	SCTP association is not yet established, or sets the data channel		the sentence could be moved to section 6.2.3], and sets the data
	state to Open if the SCTP association is already established. The		channel state to Connecting if the SCTP association is not yet
	side which starts external negotiation creates data channel using		established, or sets the data channel state to Open if the SCTP
	underlying data channel stack API and the data channel is put into		association is already established. The side which starts non-DCEP
	open state immediately (assuming ICE, SCTP procedures were already		negotiation creates a data channel using underlying data channel
	done). However, the application can't send data on this data channel		stack API and the data channel is put into open state immediately
	until external negotiation is complete with the peer. This is		(assuming ICE, SCTP procedures were already done). [Editor's note:
	because peer needs to be aware and accept the data channel via		The API related information could be deleted.] However, the
	external negotiation. The peer after accepting the data channel		application can't send data on this data channel until non-DCEP
	offer can start sending data immediately. This implies that the		negotiation is complete with the peer. This is because the peer
	offerer may get data channel message before external negotiation is		needs to be aware and accept the data channel via non-DCEP
	complete and the application should be ready to handle it.		negotiation. The peer after accepting the data channel offer can
			start sending data immediately. This implies that the offerer may
			get data channel sub-protocol messages before non-DCEP negotiation is
			complete and the application should be ready to handle it. [Editor's
			note: The information in these last four sentences could be moved to
			Section 6.2.3.]
	If the peer rejects the data channel part of the offer then it		If the peer rejects the data channel part of the offer then it
	doesn't have to do anything as the data channel was not created using		doesn't have to do anything as the data channel was not created using
	the stack. The offerer on the other hand needs to close the data		the stack. The offerer on the other hand needs to close the data
	channel that was opened by invoking relevant data channel stack API		channel that was opened by invoking relevant data channel stack API
	procedures.		procedures.
			[Editor's note: The information in the preceding paragraph could be
			moved to Section 6.2.3 (to a new bullet point there).]
	It is also worth noting that a data channel stack implementation may		It is also worth noting that a data channel stack implementation may
	not provide any API to create and close data channels; instead the		not provide any API to create and close data channels; instead the
	data channels are used on the fly as needed just by communicating via		data channels are used on the fly as needed just by communicating via
	external means or by even having some local configuration/assumptions		non-DCEP means or by even having some local configuration/assumptions
	on both the peers.		on both the peers.
	The application then externally negotiates the data channel		[Editor's note: The preceding paragraph could be deleted.]
	properties and sub-protocol properties with the peer's application.
			The application then negotiates the data channel properties and sub-
			protocol properties with the peer's application using a mechanism
			different from DCEP.
			[Editor's note: The preceding paragraph could be deleted.]
	[ASSUMPTION] The peer MUST then symmetrically create a data channel		[ASSUMPTION] The peer MUST then symmetrically create a data channel
	with these negotiated data channel properties. This is the only way		with these negotiated data channel properties. This is the only way
	for the peer's data channel stack to know which properties to apply		for the peer's data channel stack to know which properties to apply
	when transmitting data on this channel. The data channel stack MUST		when transmitting data on this channel. [Editor's note: The previous
	allow data channel creation with any non-conflicting stream		sentence could be deleted.] The data channel stack MUST allow data
	identifier so that both peers can create the data channel with the		channel creation with any non-conflicting stream identifier so that
	same stream identifier.		both peers can create the data channel with the same stream
			identifier. [Editor's note: The information in this sentence could
			be moved to Section 6.2.3.]
	In case the external negotiation is correlated with an SDP offer/		In case the non-DCEP negotiation is correlated with an SDP offer/
	answer exchange that establishes the SCTP association, the SCTP		answer exchange that establishes the SCTP association, the SCTP
	initialization completion triggers a callback from the data channel		initialization completion triggers a callback from the data channel
	stack to an application on both the ends to change the data channel		stack to an application on both the ends to change the data channel
	state from Connecting to Open. The details of this interface is		state from Connecting to Open. The details of this interface is
	specific to the data channel user application. Browser based		specific to the data channel user application. Browser based
	applications (could include hybrid apps) will use [WebRtcAPI], while		applications (could include hybrid apps) will use [WebRtcAPI], while
	native applications use a compatible API, which is yet to be		native applications use a compatible API, which is yet to be
	specified. See Section 6.2.3 for details on when the data channel		specified. See Section 6.2.3 for details on when the data channel
	stack can assume the data channel is open, and on when the		stack can assume the data channel is open, and on when the
	application can assume the data channel is open.		application can assume the data channel is open.
			[Editor's note: The preceding paragraph could be deleted.]
	5.2.3. Closing a Data Channel		5.2.3. Closing a Data Channel
	When the application requests the closing of an externally negotiated		When the application requests the closing of a non-DCEP negotiated
	data channel, the data channel stack always performs an in-band SSN		data channel, the data channel stack always performs an SCTP SSN
	reset for this channel.		reset for this channel.
	Depending upon the method used for external negotiation and the sub-		[Editor's note: The preceding paragraph could be deleted.]
			Depending upon the method used for non-DCEP negotiation and the sub-
	protocol associated with the data channel, the closing might in		protocol associated with the data channel, the closing might in
	addition be signaled to the peer via external negotiation.		addition be signaled to the peer via non-DCEP negotiation.
	6. SDP-based External Negotiation		[Editor's note: The preceding paragraph could be deleted.]
	This section defines a method of external negotiation by which two		6. SDP Offer/Answer Negotiation
			This section defines a method of non-DCEP negotiation by which two
	clients can negotiate data channel-specific and sub-protocol-specific		clients can negotiate data channel-specific and sub-protocol-specific
	parameters, using the out-of-band SDP offer/answer exchange. This		parameters, using the out-of-band SDP offer/answer exchange. This
	SDP extension can only be used with SDP offer/answer model.		SDP extension can only be used with the SDP offer/answer model.
	6.1. SDP Syntax		6.1. SDP Syntax
	Two new SDP attributes are defined to support external negotiation of		Two new SDP attributes are defined to support SDP offer/answer
	data channels. The first attribute provides for negotiation of		negotiation of data channels. The first attribute provides for
	channel-specific parameters. The second attribute provides for		negotiation of channel-specific parameters. The second attribute
	negotiation of sub-protocol-specific parameters.		provides for negotiation of sub-protocol-specific parameters.
	6.1.1. SDP Attribute for Data Channel Parameter Negotiation		6.1.1. SDP Attribute for Data Channel Parameter Negotiation
	Associated with the SDP "m" line that defines the SCTP association		Associated with the SDP "m" line that defines the SCTP association
	for data channels (defined in Section 4), each SDP offer and answer		for data channels (defined in Section 4), each SDP offer and answer
	includes one "a=dcmap:" attribute that defines the data channel		includes one "a=dcmap:" attribute that defines the data channel
	parameters for each data channel to be negotiated. Each such		parameters for each data channel to be negotiated. Each such
	attribute line specifies the following parameters for a data channel:		attribute line specifies the following parameters for a data channel:
	SCTP stream identifier, sub-protocol, label, reliability, order of		SCTP stream identifier, sub-protocol, label, reliability, order of
	delivery, and priority.		delivery, and priority.
	The intention of exchanging these attributes is to create data		The intention of exchanging these attributes is to create data
	channels on both the peers with the same set of attributes without		channels on both the peers with the same set of attributes without
	actually using [I-D.ietf-rtcweb-data-protocol]. It is assumed that		actually using the DCEP [I-D.ietf-rtcweb-data-protocol]. It is
	the data channel properties (reliable/partially reliable, ordered/		assumed that the data channel properties (reliable/partially
	unordered) are suitable per the sub-protocol transport requirements.		reliable, ordered/unordered) are suitable per the sub-protocol
			transport requirements.
	6.1.1.1. dcmap Attribute		6.1.1.1. dcmap Attribute
	"a=dcmap:" is a media level attribute having following ABNF syntax.		"a=dcmap:" is a media level attribute having following ABNF syntax.
	Formal Syntax:		Formal Syntax:
	Name: dcmap		Name: dcmap
	Value: dcmap-value		Value: dcmap-value
	skipping to change at page 10, line 9		skipping to change at page 11, line 9
	a=dcmap:0		a=dcmap:0
	a=dcmap:1 subprotocol="BFCP";max-time=60000		a=dcmap:1 subprotocol="BFCP";max-time=60000
	a=dcmap:2 subprotocol="MSRP";ordered=true;label="MSRP"		a=dcmap:2 subprotocol="MSRP";ordered=true;label="MSRP"
	a=dcmap:3 label="Label 1";ordered=false;max-retr=5		a=dcmap:3 label="Label 1";ordered=false;max-retr=5
	a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000;max-retr=3		a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000;max-retr=3
	Note: The last example (a=dcmap:4) shows a 'label' parameter value		Note: The last example (a=dcmap:4) shows a 'label' parameter value
	which contains one non-printable 'escaped-char' character (the		which contains one non-printable 'escaped-char' character (the
	tabulator character).		tabulator character).
	Within an 'a=dcmap' attribute line's 'dcmap-opt' value either only		Within an 'a=dcmap' attribute line's 'dcmap-opt' value either only
	one 'maxretr-opt' parameter or one 'maxtime-opt' parameter is		one 'maxretr-opt' parameter or one 'maxtime-opt' parameter MAY be
	present. Both MUST NOT be present.		present. Both MUST NOT be present.
	6.1.1.2. dcmap-stream-id Parameter		6.1.1.2. dcmap-stream-id Parameter
	The 'dcmap-stream-id' parameter indicates the SCTP stream identifier		The 'dcmap-stream-id' parameter indicates the SCTP stream identifier
	within the SCTP association used to form the data channel.		within the SCTP association used to form the data channel.
	6.1.1.3. label Parameter		6.1.1.3. label Parameter
	The 'label' parameter indicates the name of the channel. It		The 'label' parameter indicates the name of the channel. It
	represents a label that can be used to distinguish, in the context of		represents a label that can be used to distinguish, in the context of
	the WebRTC API, an RTCDataChannel object from other RTCDataChannel		the WebRTC API [WebRtcAPI], an RTCDataChannel object from other
	objects. This parameter maps to the 'Label' parameter defined in		RTCDataChannel objects. This parameter maps to the 'Label' parameter
	[I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is optional.		defined in [I-D.ietf-rtcweb-data-protocol]. The 'label' parameter is
	If it is not present, then its value defaults to the empty string.		optional. If it is not present, then its value defaults to the empty
			string.
	Note: The empty string may also be explicitly used as 'label' value,		Note: The empty string MAY also be explicitly used as 'label' value,
	such that 'label=""' is equivalent to the 'label' parameter not being		such that 'label=""' is equivalent to the 'label' parameter not being
	present at all. [I-D.ietf-rtcweb-data-protocol] allows the		present at all. [I-D.ietf-rtcweb-data-protocol] allows the
	DATA_CHANNEL_OPEN message's 'Label' value to be an empty string.		DATA_CHANNEL_OPEN message's 'Label' value to be an empty string.
	6.1.1.4. subprotocol Parameter		6.1.1.4. subprotocol Parameter
	The 'subprotocol' parameter indicates which protocol the client		The 'subprotocol' parameter indicates which protocol the client
	expects to exchange via the channel. 'Subprotocol' is an optional		expects to exchange via the channel. 'Subprotocol' is an optional
	parameter. If the 'subprotocol' parameter is not present, then its		parameter. If the 'subprotocol' parameter is not present, then its
	value defaults to the empty string.		value defaults to the empty string.
	6.1.1.5. max-retr Parameter		6.1.1.5. max-retr Parameter
	This parameter indicates that the data channel is partially reliable.		This parameter indicates that the data channel is partially reliable.
	The 'max-retr' parameter indicates the max times a user message will		The 'max-retr' parameter indicates the maximal number a user message
	be retransmitted. The max-retr parameter is optional. If the max-		will be retransmitted. The max-retr parameter is optional. If the
	retr parameter is not present, then the maximal number of		max-retr parameter is not present, then the maximal number of
	retransmissions is determined as per the generic SCTP retransmission		retransmissions is determined as per the generic SCTP retransmission
	rules as specified in [RFC4960]. This parameter maps to the 'Number		rules as specified in [RFC4960]. This parameter maps to the 'Number
	of RTX' parameter defined in [I-D.ietf-rtcweb-data-protocol].		of RTX' parameter defined in [I-D.ietf-rtcweb-data-protocol].
	6.1.1.6. max-time Parameter		6.1.1.6. max-time Parameter
	This parameter indicates that the data channel is partially reliable.		This parameter indicates that the data channel is partially reliable.
	A user message will no longer be transmitted or retransmitted after a		A user message will no longer be transmitted or retransmitted after a
	specified life-time given in milliseconds in the 'max-time'		specified life-time given in milliseconds in the 'max-time'
	parameter. The max-time parameter is optional. If the max-time		parameter. The max-time parameter is optional. If the max-time
	skipping to change at page 12, line 24		skipping to change at page 13, line 24
	Syntax:		Syntax:
	dcsa-value = stream-id SP attribute		dcsa-value = stream-id SP attribute
	attribute = <from-RFC4566>		attribute = <from-RFC4566>
	Example:		Example:
	a=dcsa:2 accept-types:text/plain		a=dcsa:2 accept-types:text/plain
	Note that the above reference to RFC 4566 defines were the attribute		Note that the above reference to RFC 4566 defines where the attribute
	definition can be found; it does not provide any limitation on		definition can be found; it does not provide any limitation on
	support of attributes defined in other documents in accordance with		support of attributes defined in other documents in accordance with
	this attribute definition.		this attribute definition. Note however that not all SDP attributes
			are suitable as "a=dcsa:" parameter. [IANA-SDP-Parameters] contains
			the lists of IANA registered session and media level or media level
			only SDP attributes.
	Thus in the example above, the original attribute line "a=accept-		Thus in the example above, the original attribute line "a=accept-
	types:text/plain" is represented by the attribute line "a=dcsa:2		types:text/plain" is represented by the attribute line "a=dcsa:2
	accept-types:text/plain", which specifies that this instance of MSRP		accept-types:text/plain", which specifies that this instance of MSRP
	being transported on the sctp association using the data channel with		being transported on the SCTP association using the data channel with
	stream id 2 accepts plain text files.		stream id 2 accepts plain text files.
	As opposed to the data channel "a=dcmap:" attribute parameters, these		As opposed to the data channel "a=dcmap:" attribute parameters, these
	parameters are subject to offer/answer negotiation following the		parameters are subject to offer/answer negotiation following the
	procedures defined in the sub-protocol specific documents.		procedures defined in the sub-protocol specific documents.
	The same syntax applies to any other SDP attribute required for		The same syntax applies to any other SDP attribute required for
	negotiation of this instance of the sub-protocol.		negotiation of this instance of the sub-protocol.
	Note: This document does not provide a complete specification of how		Note: This document does not provide a complete specification of how
	skipping to change at page 13, line 4		skipping to change at page 14, line 6
	The same syntax applies to any other SDP attribute required for		The same syntax applies to any other SDP attribute required for
	negotiation of this instance of the sub-protocol.		negotiation of this instance of the sub-protocol.
	Note: This document does not provide a complete specification of how		Note: This document does not provide a complete specification of how
	to negotiate the use of a data channel to transport MSRP. Procedures		to negotiate the use of a data channel to transport MSRP. Procedures
	specific to each sub-protocol such as MSRP will be documented		specific to each sub-protocol such as MSRP will be documented
	elsewhere. The use of MSRP is only an example of how the generic		elsewhere. The use of MSRP is only an example of how the generic
	procedures described herein might apply to a specific sub-protocol.		procedures described herein might apply to a specific sub-protocol.
	6.2. Procedures		6.2. Procedures
	6.2.1. Managing Stream Identifiers		6.2.1. Managing Stream Identifiers
	If an SDP offer / answer exchange (could be the initial or a		If an SDP offer/answer exchange (could be the initial or a subsequent
	subsequent one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based		one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media
	media description being accepted, and if this SDP offer / answer		description being accepted, and if this SDP offer/answer exchange
	exchange results in the establishment of a new SCTP association, then		results in the establishment of a new SCTP association, then the SDP
	the SDP offerer owns the even SCTP stream ids of this new SCTP		offerer owns the even SCTP stream ids of this new SCTP association
	association and the answerer owns the odd SCTP stream identifiers.		and the answerer owns the odd SCTP stream identifiers. If this "m"
	If this "m" line is removed from the signaling session (its port		line is removed from the signaling session (its port number set to
	number set to zero), and if usage of this or of a new UDP/DTLS/SCTP		zero), and if usage of this or of a new UDP/DTLS/SCTP or TCP/DTLS/
	or TCP/DTLS/SCTP based "m" line is renegotiated later on, then the		SCTP based "m" line is renegotiated later on, then the even and odd
	even and odd SCTP stream identifier ownership is redetermined as well		SCTP stream identifier ownership is redetermined as well as described
	as described above.		above.
	This specification allows simultaneous use of external and internal		This specification allows simultaneous use of SDP offer/answer and
	negotiation. However, a single stream is managed using one method at		DCEP negotiation. However, an SDP offer/answer exchange MUST NOT be
	a time. Stream ids that are not currently used in SDP can be used		initiated if the associated SCTP stream is already negotiated via
	for internal negotiation. Stream id allocation per SDP based		DCEP. Stream ids that are not currently used in SDP can be used for
	external negotiation may not align with DTLS role based allocation.		DCEP negotiation. Stream id allocation per SDP offer/answer
	This could cause glare conditions when one side trying to do external		negotiation may not align with DTLS role based allocation. This
	negotiation on a stream id while the other end trying to open a data		could cause glare conditions when one side trying to do SDP offer/
	channel on the same stream id using internal negotiation. To avoid		answer negotiation on a stream id while the other end trying to open
	these glare conditions this specification recommends that the data		a data channel on the same stream id using DCEP negotiation. To
	channel stack user always selects stream ids per above described SDP		avoid these glare conditions this specification recommends that the
	offer / answer rule even when internal negotiation is used. To avoid		data channel stack user always selects stream ids per above described
			SDP offer/answer rule even when DCEP negotiation is used. To avoid
	glare conditions, it is possible to come up with a different stream		glare conditions, it is possible to come up with a different stream
	id allocation scheme, but such schemes are outside the scope of this		id allocation scheme, but such schemes are outside the scope of this
	specification.		specification.
	6.2.2. Negotiating Data Channel Parameters		6.2.2. Negotiating Data Channel Parameters
	Conveying a reliable data channel is achieved by including neither		Conveying a reliable data channel is achieved by including neither
	'max-retr' nor 'max-time' in corresponding SDP offer's or answer's		'max-retr' nor 'max-time' in corresponding SDP offer's or answer's
	a=dcmap attribute line. Conveying a partially reliable data channel		a=dcmap attribute line. Conveying a partially reliable data channel
	is achieved by including only one of 'max-retr' or 'max-time'. By		is achieved by including only one of 'max-retr' or 'max-time'. By
	definition max-retr and max-time are mutually exclusive, so only one		definition max-retr and max-time are mutually exclusive, so at most
	of them can be present in a=dcmap. If an SDP offer contains both of		one of them MAY be present in a=dcmap. If an SDP offer contains both
	these parameters then the receiver of such an SDP offer MUST reject		of these parameters then the receiver of such an SDP offer MUST
	the SDP offer. If an SDP answer contains both of these parameters		reject the SDP offer. If an SDP answer contains both of these
	then the offerer MAY treat it as an error and MAY assume the		parameters then the offerer MAY treat it as an error and MAY assume
	associated SDP offer/answer failed and MAY take appropriate recovery		the associated SDP offer/answer failed and MAY take appropriate
	actions. These recovery options are outside the scope of this		recovery actions. These recovery options are outside the scope of
	specification.		this specification.
	The SDP answer SHALL echo the same subprotocol, max-retr, max-time,		The SDP answer SHALL echo the same subprotocol, max-retr, max-time,
	ordered parameters, if those were present in the offer, and MAY		ordered parameters, if those were present in the offer, and MAY
	include a label parameter. They MAY appear in any order, which could		include a label parameter. They MAY appear in any order, which could
	be different from the SDP offer, in the SDP answer.		be different from the SDP offer, in the SDP answer.
	When sending a subsequent offer or an answer, and for as long as the		When sending a subsequent offer or an answer, and for as long as the
	data channel is still open, the sender MUST replicate the same		data channel is still open, the sender MUST replicate the same
	information.		information.
	skipping to change at page 14, line 33		skipping to change at page 15, line 38
	ordered=false;max-retr=<number of retransmissions>		ordered=false;max-retr=<number of retransmissions>
	DATA_CHANNEL_PARTIAL_RELIABLE_TIMED		DATA_CHANNEL_PARTIAL_RELIABLE_TIMED
	ordered=true;max-time=<lifetime in milliseconds>		ordered=true;max-time=<lifetime in milliseconds>
	DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED		DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED
	ordered=false;max-time=<lifetime in milliseconds>		ordered=false;max-time=<lifetime in milliseconds>
	6.2.3. Opening a Data Channel		6.2.3. Opening a Data Channel
	The procedure for opening a data channel using external negotiation		The procedure for opening a data channel using SDP offer/answer
	starts with the agent preparing to send an SDP offer. If a peer		negotiation starts with the agent preparing to send an SDP offer. If
	receives an SDP offer before getting to send a new SDP offer with		a peer receives an SDP offer before starting to send a new SDP offer
	data channels that are to be externally negotiated, or loses an SDP		with data channels that are to be SDP offer/answer negotiated, or
	offer glare resolution procedure in this case, it MUST wait until the		loses an SDP offer glare resolution procedure in this case, it MUST
	ongoing SDP offer/answer completes before resuming the external		wait until the ongoing SDP offer/answer completes before resuming the
	negotiation procedure.		SDP offer/answer negotiation procedure.
	The agent that intends to send an SDP offer to create data channels		The agent that intends to send an SDP offer to create data channels
	through SDP-based external negotiation performs the following:		through SDP offer/answer negotiation performs the following:
	o Creates data channels using stream identifiers from the owned set		o Creates data channels using stream identifiers from the owned set
	(see Section 6.2.1).		(see Section 6.2.1).
	o As described in Section 5.2.2, if the SCTP association is not yet		o Generates a new SDP offer.
	established, then the newly created data channels are in the
	Connecting state, else if the SCTP association is already
	established, then the newly created data channels are in the Open
	state.
	o Generates a new SDP offer. In the case of browser based
	applications the browser generates the offer via the createOffer()
	API call [I-D.ietf-rtcweb-jsep].
	o Determines the list of stream identifiers assigned to data		o Determines the list of stream identifiers assigned to data
	channels opened through external negotiation.		channels opened through SDP offer/answer negotiation.
	o Completes the SDP offer with the dcmap and dcsa attributes needed,		o Completes the SDP offer with the dcmap and dcsa attributes needed,
	if any, for each externally-negotiated data channel, as described		if any, for each SDP offer/answer negotiated data channel, as
	in Section 6.1 and in Section 6.2.2.		described in Section 6.1 and in Section 6.2.2.
	o Sends the SDP offer.		o Sends the SDP offer.
	The peer receiving such an SDP offer performs the following:		The peer receiving such an SDP offer performs the following:
	o Parses and applies the SDP offer. Note that the typical parser		o Parses and applies the SDP offer. Note that the typical parser
	normally ignores unknown SDP attributes, which includes data		normally ignores unknown SDP attributes, which includes data
	channel related attributes.		channel related attributes.
	o Analyzes the channel parameters and sub-protocol attributes to		o Analyzes the channel parameters and sub-protocol attributes to
	determine whether to accept each offered data channel.		determine whether to accept each offered data channel.
	o For accepted data channels, it creates peer instances for the data		o For accepted data channels, it creates peer instances for the data
	channels with the agent using the channel parameters described in		channels with the agent using the channel parameters described in
	the SDP offer. Note that the agent is asked to create data		the SDP offer. Note that the agent is asked to create data
	channels with SCTP stream identifiers contained in the SDP offer		channels with SCTP stream identifiers contained in the SDP offer
	if the SDP offer is accepted.		if the SDP offer is accepted.
	o As described in Section 5.2.2, if the SCTP association is not yet
	established, then the newly created data channels are in the
	Connecting state, else if the SCTP association is already
	established, then the newly created data channels are in the Open
	state.
	o Generates an SDP answer.		o Generates an SDP answer.
	o Completes the SDP answer with the dcmap and optional dcsa		o Completes the SDP answer with the dcmap and optional dcsa
	attributes needed for each externally-negotiated data channel, as		attributes needed for each SDP offer/answer negotiated data
	described in Section 6.1 and in Section 6.2.2.		channel, as described in Section 6.1 and in Section 6.2.2.
	o Sends the SDP answer.		o Sends the SDP answer.
	The agent receiving such an SDP answer performs the following:		The agent receiving such an SDP answer performs the following:
	o Closes any created data channels (whether in Connecting or Open		o Closes any created data channels for which the expected dcmap and
	state) for which the expected dcmap and dcsa attributes are not		dcsa attributes are not present in the SDP answer.
	present in the SDP answer.
	o Applies the SDP answer.		o Applies the SDP answer.
	Any data channels in Connecting state are transitioned to the Open
	state when the SCTP association is established.
	Each agent application MUST wait to send data until it has		Each agent application MUST wait to send data until it has
	confirmation that the data channel at the peer is in the Open state.		confirmation that the data channel at the peer is instantiated. For
	For WebRTC, this is when both data channel stacks have channel		WebRTC, this is when both data channel stacks have channel parameters
	parameters instantiated. This occurs:		instantiated. This occurs:
	o At both peers when a data channel is created without an		o At both peers when a data channel is created without an
	established SCTP association, as soon as the data channel stacks		established SCTP association, as soon as the SCTP association is
	report that the data channel transitions to the Open state from		successfully established.
	the Connecting state.
	o At the agent receiving an SDP offer for which there is an		o At the agent receiving an SDP offer for which there is an
	established SCTP association, as soon as it creates an externally		established SCTP association, as soon as it creates an SDP offer/
	negotiated data channel in the Open state based on information		answer negotiated data channel based on information signaled in
	signaled in the SDP offer.		the SDP offer.
	o At the agent sending an SDP offer to create a new externally		o At the agent sending an SDP offer to create a new SDP offer/answer
	negotiated data channel for which there is an established SCTP		negotiated data channel for which there is an established SCTP
	association, when it receives the SDP answer confirming acceptance		association, when it receives the SDP answer confirming acceptance
	of the data channel or when it begins to receive data on the data		of the data channel or when it begins to receive data on the data
	channel from the peer, whichever occurs first.		channel from the peer, whichever occurs first.
	6.2.4. Closing a Data Channel		6.2.4. Closing a Data Channel
	When the application requests the closing of a data channel that was		When the application requests the closing of a data channel that was
	externally negotiated, the data channel stack always performs an in-		negotiated via SDP offer/answer, the data channel stack always
	band SSN reset for this channel.		performs an SCTP SSN reset for this channel.
	It is specific to the sub-protocol whether this closing MUST in		It is specific to the sub-protocol whether this closing MUST in
	addition be signaled to the peer via a new SDP offer/answer exchange.		addition be signaled to the peer via a new SDP offer/answer exchange.
	The intention to close a data channel can be signaled by sending a		The intention to close a data channel can be signaled by sending a
	new SDP offer which excludes the "a=dcmap:" and "a=dcsa:" attribute		new SDP offer which excludes the "a=dcmap:" and "a=dcsa:" attribute
	lines for the data channel. The offerer SHOULD NOT change the port		lines for the data channel. The offerer SHOULD NOT change the port
	value for the "m" line (e.g. to zero) when closing a data channel		value for the "m" line (e.g. to zero) when closing a data channel
	(unless all data channels are being closed and the SCTP association		(unless all data channels are being closed and the SCTP association
	is no longer needed), since this would close the SCTP association and		is no longer needed), since this would close the SCTP association and
	skipping to change at page 17, line 17		skipping to change at page 17, line 51
	If a new SDP offer/answer is used to close data channels then the		If a new SDP offer/answer is used to close data channels then the
	data channel(s) SHOULD only be closed by the answerer/offerer after a		data channel(s) SHOULD only be closed by the answerer/offerer after a
	successful SDP answer is sent/received.		successful SDP answer is sent/received.
	This delayed closure is RECOMMENDED in order to handle cases where		This delayed closure is RECOMMENDED in order to handle cases where
	a successful SDP answer is not received, in which case the state		a successful SDP answer is not received, in which case the state
	of the session SHOULD be kept per the last successful SDP offer/		of the session SHOULD be kept per the last successful SDP offer/
	answer.		answer.
	If a client receives a data channel close indication (due to inband		If a client receives a data channel close indication (due to inband
	SSN reset or some other reason) without associated SDP offer then the		SCTP SSN reset or some other reason) without associated SDP offer
	client SHOULD generate an SDP offer which excludes this closed data		then the client SHOULD generate an SDP offer which excludes this
	channel.		closed data channel.
	The application MUST also close any data channel that was externally		The application MUST also close any data channel that was negotiated
	negotiated, for which the stream identifiers are not listed in an		via SDP offer/answer, for which the stream identifiers are not listed
	incoming SDP offer.		in an incoming SDP offer.
	A closed data channel using local close (SCTP reset), without an		A closed data channel using local close (SCTP SSN reset), without an
	additional SDP offer/answer to close it, may be reused for a new data		additional SDP offer/answer to close it, may be reused for a new data
	channel. This can only be done via new SDP offer/answer, describing		channel. This can only be done via new SDP offer/answer, describing
	the new sub-protocol and its attributes, only after the corresponding		the new sub-protocol and its attributes, only after the corresponding
	data channel close acknowledgement is received from the peer (i.e.		data channel close acknowledgement is received from the peer (i.e.
	SCTP reset of both incoming and outgoing streams is completed). This		SCTP SSN reset of both incoming and outgoing streams is completed).
	restriction is to avoid the race conditions between arrival of "SDP		This restriction is to avoid the race conditions between arrival of
	offer which reuses stream" with "SCTP reset which closes outgoing		"SDP offer which reuses stream" with "SCTP SSN reset which closes
	stream" at the peer		outgoing stream" at the peer.
	6.2.5. Various SDP Offer/Answer Scenarios and Considerations		6.2.5. Various SDP Offer/Answer Scenarios and Considerations
	SDP offer has no a=dcmap attributes		SDP offer has no a=dcmap attributes
	* Initial SDP offer: No data channel is negotiated yet. The DTLS		* Initial SDP offer: No data channel is negotiated yet. The DTLS
	connection and SCTP association is negotiated and, if agreed,		connection and SCTP association is negotiated and, if agreed,
	established as per [I-D.ietf-mmusic-sctp-sdp].		established as per [I-D.ietf-mmusic-sctp-sdp].
	* Subsequent SDP offer: All the externally negotiated data		* Subsequent SDP offer: All the SDP offer/answer negotiated data
	channels are expected be closed now. The DTLS/SCTP association		channels are expected be closed now. The DTLS/SCTP association
	remains open for external or internal negotiation of data		remains open for SDP offer/answer or DCEP negotiation of data
	channels.		channels.
	SDP answer has no a=dcmap attributes		SDP answer has no a=dcmap attributes
	* Initial SDP answer: Either the peer does not support dcmap		* Initial SDP answer: Either the peer does not support dcmap
	attributes or it rejected all the data channels. In either		attributes or it rejected all the data channels. In either
	case offerer closes all the externally negotiated data channels		case the offerer closes all the SDP offer/answer negotiated
	that were open at the time of initial offer. The DTLS/SCTP		data channels that were open at the time of initial offer. The
	association will still be setup.		DTLS connection and SCTP association will still be setup.
	* Subsequent SDP answer: All the externally negotiated data		* Subsequent SDP answer: All the SDP offer/answer negotiated data
	channels are expected be closed now. The DTLS/SCTP association		channels are expected be closed now. The DTLS/SCTP association
	remains open for future external or internal negotiation of		remains open for future SDP offer/answer or DCEP negotiation of
	data channels.		data channels.
	SDP offer has no a=dcsa attributes for a data channel.		SDP offer has no a=dcsa attributes for a data channel.
	* This is allowed and indicates there are no sub-protocol		* This is allowed and indicates there are no sub-protocol
	parameters to convey.		parameters to convey.
	SDP answer has no a=dcsa attributes for a data channel.		SDP answer has no a=dcsa attributes for a data channel.
	* This is allowed and indicates there are no sub-protocol		* This is allowed and indicates there are no sub-protocol
	skipping to change at page 19, line 5		skipping to change at page 19, line 40
	a=setup:passive		a=setup:passive
	a=connection:new		a=connection:new
	a=fingerprint:SHA-1 \		a=fingerprint:SHA-1 \
	5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA		5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
	Figure 1: Example 1		Figure 1: Example 1
	In the above example the SDP answerer rejected the data channel with		In the above example the SDP answerer rejected the data channel with
	stream id 0 either for explicit reasons or because it does not		stream id 0 either for explicit reasons or because it does not
	understand the a=dcmap attribute. As a result the offerer will close		understand the a=dcmap attribute. As a result the offerer will close
	the data channel created with the external negotiation option. The		the data channel created with the SDP offer/answer negotiation
	SCTP association will still be setup over DTLS. At this point the		option. The SCTP association will still be setup over DTLS. At this
	offerer or the answerer may use internal negotiation to open data		point the offerer or the answerer may use DCEP negotiation to open
	channels.		data channels.
	SDP offer:		SDP offer:
	m=application 10001 UDP/DTLS/SCTP webrtc-datachannel		m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
	c=IN IP4 10.10.10.1		c=IN IP4 10.10.10.1
	a=max-message-size:100000		a=max-message-size:100000
	a=sctp-port 5000		a=sctp-port 5000
	a=setup:actpass		a=setup:actpass
	a=connection:new		a=connection:new
	a=fingerprint:SHA-1 \		a=fingerprint:SHA-1 \
	4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB		4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
	skipping to change at page 19, line 39		skipping to change at page 20, line 34
	a=setup:passive		a=setup:passive
	a=connection:new		a=connection:new
	a=fingerprint:SHA-1 \		a=fingerprint:SHA-1 \
	5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA		5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
	a=dcmap:2 subprotocol="MSRP";label="MSRP"		a=dcmap:2 subprotocol="MSRP";label="MSRP"
	a=dcsa:2 accept-types:message/cpim text/plain		a=dcsa:2 accept-types:message/cpim text/plain
	a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc		a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc
	Figure 2: Example 2		Figure 2: Example 2
	In the above example SDP offer contains data channels for BFCP and		In the above example the SDP offer contains data channels for BFCP
	MSRP sub-protocols. SDP answer rejected BFCP and accepted MSRP. So,		and MSRP sub-protocols. The SDP answer rejected BFCP and accepted
	the offerer should close the data channel for BFCP and both offerer		MSRP. So, the offerer should close the data channel for BFCP and
	and answerer may start using MSRP data channel (after SCTP/DTLS		both offerer and answerer may start using the MSRP data channel
	association is setup). The data channel with stream id 0 is free and		(after SCTP/DTLS association is setup). The data channel with stream
	can be used for future internal or external negotiation.		id 0 is free and can be used for future DCEP or SDP offer/answer
			negotiation.
	Continuing on the earlier example in Figure 1.		Continuing on the earlier example in Figure 1.
	Subsequent SDP offer:		Subsequent SDP offer:
	m=application 10001 UDP/DTLS/SCTP webrtc-datachannel		m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
	c=IN IP4 10.10.10.1		c=IN IP4 10.10.10.1
	a=max-message-size:100000		a=max-message-size:100000
	a=sctp-port 5000		a=sctp-port 5000
	a=setup:actpass		a=setup:actpass
	a=connection:existing		a=connection:existing
	skipping to change at page 20, line 35		skipping to change at page 21, line 35
	a=fingerprint:SHA-1 \		a=fingerprint:SHA-1 \
	5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA		5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
	a=dcmap:4 subprotocol="MSRP";label="MSRP"		a=dcmap:4 subprotocol="MSRP";label="MSRP"
	a=dcsa:4 accept-types:message/cpim text/plain		a=dcsa:4 accept-types:message/cpim text/plain
	a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc		a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc
	Figure 3: Example 3		Figure 3: Example 3
	The above example is a continuation of the example in Figure 1. The		The above example is a continuation of the example in Figure 1. The
	SDP offer now removes the MSRP data channel with stream id 2, but		SDP offer now removes the MSRP data channel with stream id 2, but
	opens a new MSRP data channel with stream id 4. The answerer		opens a new MSRP data channel with stream id 4. The answerer accepts
	accepted the entire offer. As a result the offerer closes the		the entire offer. As a result the offerer closes the earlier
	earlier negotiated MSRP related data channel and both offerer and		negotiated MSRP related data channel and both offerer and answerer
	answerer may start using new the MSRP related data channel.		may start using new the MSRP related data channel.
	8. Security Considerations		8. Security Considerations
	No security considerations are envisaged beyond those already		No security considerations are envisaged beyond those already
	documented in [RFC4566]		documented in [RFC4566].
	9. IANA Considerations		9. IANA Considerations
	9.1. Subprotocol identifiers		9.1. Subprotocol Identifiers
	Registration of new subprotocol identifiers is performed using the		Registration of new subprotocol identifiers is performed using the
	existing IANA table "WebSocket Subprotocol Name Registry".		existing IANA table "WebSocket Subprotocol Name Registry".
	The following text should be added following the title of the table.		The following text should be added following the title of the table.
	"This table also includes subprotocol identifiers specified for usage		"This table also includes subprotocol identifiers specified for usage
	within a WebRTC data channel."		within a WebRTC data channel."
	The following reference should be added to under the heading		The following reference should be added to under the heading
	reference: "RFC XXXX".		reference: "RFC XXXX".
	This document assigns no new values to this table.		This document assigns no new values to this table.
	NOTE to RFC Editor: Please replace "XXXX" with the number of this		NOTE to RFC Editor: Please replace "XXXX" with the number of this
	RFC.		RFC.
			9.2. New SDP Attributes
			9.2.1. dcmap
			[Editor's note: This section still needs to be completed.]
			9.2.2. dcsa
			[Editor's note: This section still needs to be completed.]
	10. Acknowledgments		10. Acknowledgments
	The authors wish to acknowledge the borrowing of ideas from other		The authors wish to acknowledge the borrowing of ideas from other
	internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley		internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley
	and Gavin Llewellyn, and to thank Christian Groves, Christer		and Gavin Llewellyn, and to thank Roni Even, Christian Groves,
	Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe Rauschenbach for		Christer Holmberg, Paul Kyzivat, Jonathan Lennox, and Uwe
	their invaluable comments.		Rauschenbach for their invaluable comments.
	11. CHANGE LOG		11. CHANGE LOG
	11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01'		11.1. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-02'
			o Move of reference [I-D.ietf-rtcweb-jsep] from the list of
			normative references to the list of informative references.
			o Addition of [IANA-SDP-Parameters] to the list of informative
			references and addition of following two sentences to the first
			paragraph after the ABNF definition: "Note however that not all
			SDP attributes are suitable as "a=dcsa:" parameter.
			[IANA-SDP-Parameters] contains the lists of IANA registered
			session and media level or media level only SDP attributes."
			o In the introduction replacement of last sentence "This document
			defines SDP-based out-of-band negotiation procedures to establish
			data channels for transport of well-defined sub-protocols" with
			"This document defines SDP offer/answer negotiation procedures to
			establish data channels for transport of well-defined sub-
			protocols, to enable out-of-band negotiation".
			o Throughout the document replacement of "external negotiation" with
			"SDP offer/answer negotiation" and removal of term "external
			negotiation" from the terminology list in Section 3.
			o Throughout the document replacement of "internal negotiation" with
			"DCEP" and removal of terms "internal negotiation" and "in-band
			negotiation" from the terminology list in Section 3.
			o Addition of "SCTP Stream Sequence Number (SSN)" to the list of
			terms.
			o In Section 6.2.1 replacement of sentence "However, a single stream
			is managed using one method at a time." with "However, an SDP
			offer/answer exchange MUST NOT be initiated if the associated SCTP
			stream is already negotiated via DCEP".
			o In Section 6.2.2 replacement of sentence "By definition max-retr
			and max-time are mutually exclusive, so only one of them can be
			present in a=dcmap" with "By definition max-retr and max-time are
			mutually exclusive, so at most one of them MAY be present in
			a=dcmap".
			o Move of reference [WebRtcAPI] from list of normative references to
			list of informative references.
			o Removal of almost all text parts, which discussed JavaScript or
			other API specific aspects. Such API specific aspects were mainly
			discussed in sub-sections of Section 5 and Section 6.
			11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-01'
	o New Section 4 regarding applicability to SDP offer/answer only.		o New Section 4 regarding applicability to SDP offer/answer only.
	o Addition of new Section 9.1 "Subprotocol identifiers" as		o Addition of new Section 9.1 "Subprotocol identifiers" as
	subsection of the "IANA Considerations" related Section 9. Also		subsection of the "IANA Considerations" related Section 9. Also
	removal of the temporary note "To be completed. As [I-D.ietf-		removal of the temporary note "To be completed. As [I-D.ietf-
	rtcweb-data-protocol] this document should refer to IANA's		rtcweb-data-protocol] this document should refer to IANA's
	WebSocket Subprotocol Name Registry defined in [RFC6455]."		WebSocket Subprotocol Name Registry defined in [RFC6455]."
	o In Section 6.2.2:		o In Section 6.2.2:
	skipping to change at page 23, line 31		skipping to change at page 25, line 44
	* In the last but one paragraph replacement of "must" with "The		* In the last but one paragraph replacement of "must" with "The
	application MUST also close...".		application MUST also close...".
	o In Section 6.1.2 addition of following note after the formal		o In Section 6.1.2 addition of following note after the formal
	definition of the 'a=dcsa' attribute: "Note that the above		definition of the 'a=dcsa' attribute: "Note that the above
	reference to RFC 4566 defines were the attribute definition can be		reference to RFC 4566 defines were the attribute definition can be
	found; it does not provide any limitation on support of attributes		found; it does not provide any limitation on support of attributes
	defined in other documents in accordance with this attribute		defined in other documents in accordance with this attribute
	definition."		definition."
	11.2. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00'		11.3. Changes against 'draft-ietf-mmusic-data-channel-sdpneg-00'
	o In Section 3 "WebRTC data channel" was defined as "A bidirectional		o In Section 3 "WebRTC data channel" was defined as "A bidirectional
	channel consisting of paired SCTP outbound and inbound streams."		channel consisting of paired SCTP outbound and inbound streams."
	Replacement of this definition with "Data channel: A WebRTC data		Replacement of this definition with "Data channel: A WebRTC data
	channel as specified in [I-D.ietf-rtcweb-data-channel]", and		channel as specified in [I-D.ietf-rtcweb-data-channel]", and
	consistent usage of "data channel" in the remainder of the		consistent usage of "data channel" in the remainder of the
	document including the document's headline."		document including the document's headline."
	o In Section 5 removal of following note: 'OPEN ISSUE: The syntax in		o In Section 5 removal of following note: 'OPEN ISSUE: The syntax in
	[I-D.ietf-mmusic-sctp-sdp] may change as that document progresses.		[I-D.ietf-mmusic-sctp-sdp] may change as that document progresses.
	skipping to change at page 24, line 48		skipping to change at page 27, line 15
	o In Section 6.1.2's second paragraph replacement of "sctp stream		o In Section 6.1.2's second paragraph replacement of "sctp stream
	identifier" with "SCTP stream identifier".		identifier" with "SCTP stream identifier".
	o In first paragraph of Section 6.2.1 replacement of first two		o In first paragraph of Section 6.2.1 replacement of first two
	sentences 'For the SDP-based external negotiation described in		sentences 'For the SDP-based external negotiation described in
	this document, the initial offerer based "SCTP over DTLS" owns by		this document, the initial offerer based "SCTP over DTLS" owns by
	convention the even stream identifiers whereas the initial		convention the even stream identifiers whereas the initial
	answerer owns the odd stream identifiers. This ownership is		answerer owns the odd stream identifiers. This ownership is
	invariant for the whole lifetime of the signaling session, e.g. it		invariant for the whole lifetime of the signaling session, e.g. it
	does not change if the initial answerer sends a new offer to the		does not change if the initial answerer sends a new offer to the
	initial offerer.' with 'If an SDP offer / answer exchange (could		initial offerer.' with 'If an SDP offer/answer exchange (could be
	be the initial or a subsequent one) results in a UDP/DTLS/SCTP or		the initial or a subsequent one) results in a UDP/DTLS/SCTP or
	TCP/DTLS/SCTP based media description being accepted, and if this		TCP/DTLS/SCTP based media description being accepted, and if this
	SDP offer / answer exchange results in the establishment of a new		SDP offer/answer exchange results in the establishment of a new
	SCTP association, then the SDP offerer owns the even SCTP stream		SCTP association, then the SDP offerer owns the even SCTP stream
	ids of this new SCTP association and the answerer owns the odd		ids of this new SCTP association and the answerer owns the odd
	SCTP stream identifiers. If this "m" line is removed from the		SCTP stream identifiers. If this "m" line is removed from the
	signaling session (its port number set to zero), and if usage of		signaling session (its port number set to zero), and if usage of
	this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is		this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is
	renegotiated later on, then the even and odd SCTP stream		renegotiated later on, then the even and odd SCTP stream
	identifier ownership is redetermined as well as described above.'		identifier ownership is redetermined as well as described above.'
	o In Section 6.2.3 the first action of an SDP answerer, when		o In Section 6.2.3 the first action of an SDP answerer, when
	receiving an SDP offer, was described as "Applies the SDP offer.		receiving an SDP offer, was described as "Applies the SDP offer.
	skipping to change at page 26, line 16		skipping to change at page 28, line 30
	to handle cases where a successful SDP answer is not received, in		to handle cases where a successful SDP answer is not received, in
	which case the state of the session SHOULD be kept per the last		which case the state of the session SHOULD be kept per the last
	successful SDP offer/answer."		successful SDP offer/answer."
	o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects		o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects
	Section 6.1.1 contained already procedural descriptions related to		Section 6.1.1 contained already procedural descriptions related to
	data channel reliability negotiation. Creation of new		data channel reliability negotiation. Creation of new
	Section 6.2.2 and moval of reliability negotiation related text to		Section 6.2.2 and moval of reliability negotiation related text to
	this new section.		this new section.
	11.3. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02'		11.4. Changes against 'draft-ejzak-mmusic-data-channel-sdpneg-02'
	o Removal of note "[ACTION ITEM]" from section "subprotocol		o Removal of note "[ACTION ITEM]" from section "subprotocol
	parameter". As [I-D.ietf-rtcweb-data-protocol] this document		parameter". As [I-D.ietf-rtcweb-data-protocol] this document
	should refer to IANA's WebSocket Subprotocol Name Registry defined		should refer to IANA's WebSocket Subprotocol Name Registry defined
	in [RFC6455].		in [RFC6455].
	o In whole document, replacement of "unreliable" with "partially		o In whole document, replacement of "unreliable" with "partially
	reliable", which is used in [I-D.ietf-rtcweb-data-channel] and in		reliable", which is used in [I-D.ietf-rtcweb-data-channel] and in
	[I-D.ietf-rtcweb-data-protocol] in most places.		[I-D.ietf-rtcweb-data-protocol] in most places.
	skipping to change at page 27, line 19		skipping to change at page 29, line 32
	o In the "Examples" section, in the first two SDP offer examples in		o In the "Examples" section, in the first two SDP offer examples in
	the a=dcmap attribute lines 'label="BGCP"' was replaced with		the a=dcmap attribute lines 'label="BGCP"' was replaced with
	'label="BFCP"'.		'label="BFCP"'.
	o In all examples, the "m" line proto value "DTLS/SCTP" was replaced		o In all examples, the "m" line proto value "DTLS/SCTP" was replaced
	with "UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were		with "UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were
	replaced with "a=max-message-size" attribute lines, as per draft-		replaced with "a=max-message-size" attribute lines, as per draft-
	ietf-mmusic-sctp-sdp-12.		ietf-mmusic-sctp-sdp-12.
	11.4. Changes against '-01'		11.5. Changes against '-01'
	o Formal syntax for dcmap and dcsa attribute lines.		o Formal syntax for dcmap and dcsa attribute lines.
	o Making subprotocol as an optional parameter in dcmap.		o Making subprotocol as an optional parameter in dcmap.
	o Specifying disallowed parameter combinations for max-time and max-		o Specifying disallowed parameter combinations for max-time and max-
	retr.		retr.
	o Clarifications on WebRTC data channel close procedures.		o Clarifications on WebRTC data channel close procedures.
	11.5. Changes against '-00'		11.6. Changes against '-00'
	o Revisions to identify difference between internal and external		o Revisions to identify difference between internal and external
	negotiation and their usage.		negotiation and their usage.
	o Introduction of more generic terminology, e.g. "application"		o Introduction of more generic terminology, e.g. "application"
	instead of "browser".		instead of "browser".
	o Clarification of how "max-retr and max-time affect the usage of		o Clarification of how "max-retr and max-time affect the usage of
	unreliable and reliable WebRTC data channels.		unreliable and reliable WebRTC data channels.
	skipping to change at page 28, line 10		skipping to change at page 30, line 21
	o Removal of the SCTP port number from the a=dcmap and a=dcsa		o Removal of the SCTP port number from the a=dcmap and a=dcsa
	attributes as this is now contained in the a=sctp-port attribute,		attributes as this is now contained in the a=sctp-port attribute,
	and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP		and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP
	association on top of the DTLS connection.		association on top of the DTLS connection.
	12. References		12. References
	12.1. Normative References		12.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<http://www.rfc-editor.org/info/rfc2119>.
	[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session		[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
	Description Protocol", RFC 4566, July 2006.		Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
			July 2006, <http://www.rfc-editor.org/info/rfc4566>.
	[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model		[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
	with Session Description Protocol (SDP)", RFC 3264, June		with Session Description Protocol (SDP)", RFC 3264,
	2002.		DOI 10.17487/RFC3264, June 2002,
			<http://www.rfc-editor.org/info/rfc3264>.
	[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
	Specifications: ABNF", STD 68, RFC 5234, January 2008.
	[I-D.ietf-rtcweb-jsep]		[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
	Uberti, J., Jennings, C., and E. Rescorla, "Javascript		Specifications: ABNF", STD 68, RFC 5234,
	Session Establishment Protocol", draft-ietf-rtcweb-jsep-09		DOI 10.17487/RFC5234, January 2008,
	(work in progress), March 2015.		<http://www.rfc-editor.org/info/rfc5234>.
	[I-D.ietf-rtcweb-data-channel]		[I-D.ietf-rtcweb-data-channel]
	Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data		Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
	Channels", draft-ietf-rtcweb-data-channel-13 (work in		Channels", draft-ietf-rtcweb-data-channel-13 (work in
	progress), January 2015.		progress), January 2015.
	[I-D.ietf-mmusic-sctp-sdp]		[I-D.ietf-mmusic-sctp-sdp]
	Holmberg, C., Loreto, S., and G. Camarillo, "Stream		Holmberg, C., Loreto, S., and G. Camarillo, "Stream
	Control Transmission Protocol (SCTP)-Based Media Transport		Control Transmission Protocol (SCTP)-Based Media Transport
	in the Session Description Protocol (SDP)", draft-ietf-		in the Session Description Protocol (SDP)", draft-ietf-
	mmusic-sctp-sdp-14 (work in progress), March 2015.		mmusic-sctp-sdp-14 (work in progress), March 2015.
	[WebRtcAPI]
	Bergkvist, A., Burnett, D., Jennings, C., and A.
	Narayanan, "WebRTC 1.0: Real-time Communication Between
	Browsers", World Wide Web Consortium WD-webrtc-20130910,
	September 2013,
	<http://www.w3.org/TR/2013/WD-webrtc-20130910/>.
	12.2. Informative References		12.2. Informative References
	[I-D.ietf-rtcweb-data-protocol]		[I-D.ietf-rtcweb-data-protocol]
	Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel		Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel
	Establishment Protocol", draft-ietf-rtcweb-data-		Establishment Protocol", draft-ietf-rtcweb-data-
	protocol-09 (work in progress), January 2015.		protocol-09 (work in progress), January 2015.
	[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC		[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
	4960, September 2007.		RFC 4960, DOI 10.17487/RFC4960, September 2007,
			<http://www.rfc-editor.org/info/rfc4960>.
	[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message		[RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
	Session Relay Protocol (MSRP)", RFC 4975, September 2007.		"The Message Session Relay Protocol (MSRP)", RFC 4975,
			DOI 10.17487/RFC4975, September 2007,
			<http://www.rfc-editor.org/info/rfc4975>.
	[RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions		[RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
	for the Message Sessions Relay Protocol (MSRP)", RFC 4976,		for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
	September 2007.		DOI 10.17487/RFC4976, September 2007,
			<http://www.rfc-editor.org/info/rfc4976>.
	[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,		[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
	and P. Kyzivat, "A Session Description Protocol (SDP)		and P. Kyzivat, "A Session Description Protocol (SDP)
	Offer/Answer Mechanism to Enable File Transfer", RFC 5547,		Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
	May 2009.		DOI 10.17487/RFC5547, May 2009,
			<http://www.rfc-editor.org/info/rfc5547>.
	[RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model		[RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model
	for the Message Session Relay Protocol (MSRP)", RFC 6135,		for the Message Session Relay Protocol (MSRP)", RFC 6135,
	February 2011.		DOI 10.17487/RFC6135, February 2011,
			<http://www.rfc-editor.org/info/rfc6135>.
	[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC		[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
	6455, December 2011.		RFC 6455, DOI 10.17487/RFC6455, December 2011,
			<http://www.rfc-editor.org/info/rfc6455>.
	[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection		[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
	Establishment for Media Anchoring (CEMA) for the Message		Establishment for Media Anchoring (CEMA) for the Message
	Session Relay Protocol (MSRP)", RFC 6714, August 2012.		Session Relay Protocol (MSRP)", RFC 6714,
			DOI 10.17487/RFC6714, August 2012,
			<http://www.rfc-editor.org/info/rfc6714>.
			[I-D.ietf-rtcweb-jsep]
			Uberti, J., Jennings, C., and E. Rescorla, "Javascript
			Session Establishment Protocol", draft-ietf-rtcweb-jsep-11
			(work in progress), July 2015.
			[IANA-SDP-Parameters]
			"Session Description Protocol (SDP) Parameters", Internet
			Assigned Numbers Authority Protocol Assignments Session
			Description Protocol (SDP) Parameters,
			<http://www.iana.org/assignments/sdp-parameters/
			sdp-parameters.xhtml>.
			[WebRtcAPI]
			Bergkvist, A., Burnett, D., Jennings, C., and A.
			Narayanan, "WebRTC 1.0: Real-time Communication Between
			Browsers", World Wide Web Consortium WD-webrtc-20150210,
			February 2015,
			<http://www.w3.org/TR/2015/WD-webrtc-20150210/>.
	Authors' Addresses		Authors' Addresses
	Keith Drage (editor)		Keith Drage (editor)
	Alcatel-Lucent		Alcatel-Lucent
	Quadrant, Stonehill Green, Westlea		Quadrant, Stonehill Green, Westlea
	Swindon		Swindon
	UK		UK
	Email: keith.drage@alcatel-lucent.com		Email: keith.drage@alcatel-lucent.com
End of changes. 109 change blocks.
	307 lines changed or deleted		408 lines changed or added
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