--- 1/draft-ietf-mmusic-data-channel-sdpneg-15.txt 2017-12-25 02:13:09.020455257 -0800 +++ 2/draft-ietf-mmusic-data-channel-sdpneg-16.txt 2017-12-25 02:13:09.100457150 -0800 @@ -1,25 +1,25 @@ MMUSIC K. Drage Internet-Draft Unaffiliated Intended status: Standards Track M. Makaraju -Expires: June 7, 2018 Nokia +Expires: June 28, 2018 Nokia J. Stoetzer-Bradler R. Ejzak J. Marcon Unaffiliated R. Even, Ed. Huawei - December 4, 2017 + December 25, 2017 SDP-based Data Channel Negotiation - draft-ietf-mmusic-data-channel-sdpneg-15 + draft-ietf-mmusic-data-channel-sdpneg-16 Abstract The Real-Time Communication in WEB-browsers (RTCWeb) working group is charged to provide protocols to support direct interactive rich communications using audio, video, and data between two peers' web- browsers. For the support of data communication, the RTCWeb working group has in particular defined the concept of bi-directional data channels over SCTP (Stream Control Transmission Protocol), where each data channel might be used to transport other protocols, called @@ -42,147 +42,152 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference 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 (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 - 5. SDP Offer/Answer Negotiation . . . . . . . . . . . . . . . . 6 - 5.1. SDP Syntax . . . . . . . . . . . . . . . . . . . . . . . 6 + 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 + 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 6 + 5. SDP Data Channel attributes . . . . . . . . . . . . . . . . . 6 + 5.1. SDP data channel attributes . . . . . . . . . . . . . . . 6 5.1.1. SDP Attribute for Data Channel Parameter Negotiation 6 5.1.2. Other Media Level Attributes . . . . . . . . . . . . 10 - 5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 12 - 5.2.1. Managing Stream Identifiers . . . . . . . . . . . . . 12 - 5.2.2. Negotiating Data Channel Parameters . . . . . . . . . 13 - 5.2.3. Opening a Data Channel . . . . . . . . . . . . . . . 14 - 5.2.4. Closing a Data Channel . . . . . . . . . . . . . . . 16 - 5.2.5. Various SDP Offer/Answer Scenarios and Considerations 17 - 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 - 8.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 21 - 8.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 21 - 8.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 21 - 8.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 22 - 8.3. New Usage Level . . . . . . . . . . . . . . . . . . . . . 22 - 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 - 10. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 23 - 10.1. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-14' . . . . . . . . . . . . . . . . . . . . . . . 23 - - 10.2. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-12' . . . . . . . . . . . . . . . . . . . . . . . 23 - 10.3. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-11' . . . . . . . . . . . . . . . . . . . . . . . 23 - 10.4. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-10' . . . . . . . . . . . . . . . . . . . . . . . 24 - 10.5. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-09' . . . . . . . . . . . . . . . . . . . . . . . 24 - 10.6. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-08' . . . . . . . . . . . . . . . . . . . . . . . 25 - 10.7. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-07' . . . . . . . . . . . . . . . . . . . . . . . 25 - 10.8. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-06' . . . . . . . . . . . . . . . . . . . . . . . 25 - 10.9. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 25 - 10.10. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 26 - 10.11. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 27 - 10.12. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 28 - 10.13. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 29 - 10.14. Changes against 'draft-ietf-mmusic-data-channel- - sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 31 - 10.15. Changes against 'draft-ejzak-mmusic-data-channel- - sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 34 - 10.16. Changes against '-01' . . . . . . . . . . . . . . . . . 35 - 10.17. Changes against '-00' . . . . . . . . . . . . . . . . . 35 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 36 - 11.2. Informative References . . . . . . . . . . . . . . . . . 37 + 6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 12 + 6.1. Managing Stream Identifiers . . . . . . . . . . . . . . . 12 + 6.2. Negotiating Data Channel Parameters . . . . . . . . . . . 13 + 6.3. Generating initial Offer . . . . . . . . . . . . . . . . 14 + 6.4. Generating SDP answer . . . . . . . . . . . . . . . . . . 15 + 6.5. Offerer Processing of the SDP Answer . . . . . . . . . . 15 + 6.6. Closing a Data Channel . . . . . . . . . . . . . . . . . 16 + 6.7. Various SDP Offer/Answer Scenarios and Considerations . . 17 + 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 21 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 + 9.1. Subprotocol Identifiers . . . . . . . . . . . . . . . . . 22 + 9.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 22 + 9.2.1. dcmap . . . . . . . . . . . . . . . . . . . . . . . . 22 + 9.2.2. dcsa . . . . . . . . . . . . . . . . . . . . . . . . 23 + 9.3. New Usage Level . . . . . . . . . . . . . . . . . . . . . 23 + 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 + 11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 24 + 11.1. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-15' . . . . . . . . . . . . . . . . . . . . . . . 24 + 11.2. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-14' . . . . . . . . . . . . . . . . . . . . . . . 24 + 11.3. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-12' . . . . . . . . . . . . . . . . . . . . . . . 24 + 11.4. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-11' . . . . . . . . . . . . . . . . . . . . . . . 24 + 11.5. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-10' . . . . . . . . . . . . . . . . . . . . . . . 25 + 11.6. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-09' . . . . . . . . . . . . . . . . . . . . . . . 25 + 11.7. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-08' . . . . . . . . . . . . . . . . . . . . . . . 26 + 11.8. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-07' . . . . . . . . . . . . . . . . . . . . . . . 26 + 11.9. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-06' . . . . . . . . . . . . . . . . . . . . . . . 26 + 11.10. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-05' . . . . . . . . . . . . . . . . . . . . . . . 26 + 11.11. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-04' . . . . . . . . . . . . . . . . . . . . . . . 27 + 11.12. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-03' . . . . . . . . . . . . . . . . . . . . . . . 28 + 11.13. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 29 + 11.14. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-01' . . . . . . . . . . . . . . . . . . . . . . . 30 + 11.15. Changes against 'draft-ietf-mmusic-data-channel- + sdpneg-00' . . . . . . . . . . . . . . . . . . . . . . . 32 + 11.16. Changes against 'draft-ejzak-mmusic-data-channel- + sdpneg-02' . . . . . . . . . . . . . . . . . . . . . . . 35 + 11.17. Changes against '-01' . . . . . . . . . . . . . . . . . 36 + 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 - Using DCEP . . . . . . . . . . . . . . . . . . . . . 37 - A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 38 - A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 39 - A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 39 - A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 39 - A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 40 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 + Using DCEP . . . . . . . . . . . . . . . . . . . . . 39 + A.1. Stream Identifier Numbering . . . . . . . . . . . . . . . 39 + A.2. Generic Data Channel Negotiation Not Using DCEP . . . . . 40 + A.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 40 + A.2.2. Opening a Data Channel . . . . . . . . . . . . . . . 40 + A.2.3. Closing a Data Channel . . . . . . . . . . . . . . . 41 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 1. Introduction The RTCWeb working group has defined the concept of bi-directional data channels running on top of the Stream Control Transmission - Protocol (SCTP). RTCWeb allows applications to use data channels. - RTCWeb defines an in-band Data Channel Establishment Protocol (DCEP), - however other in-band or out-of-band protocols may be used for - establishing data channels. Each data channel consists of paired - SCTP streams sharing the same SCTP Stream Identifier. Data channels - are created by endpoint applications through the WebRTC API - (Application Programming Interface), or other users of a data channel - like CLUE. They can be used to transport proprietary or well-defined - protocols, which in the latter case can be signaled by the data - channel "subprotocol" parameter, conceptually similar to the - WebSocket "subprotocol". However, apart from the "subprotocol" value - transmitted to the peer, RTCWeb leaves it open how endpoint - applications can agree on how to instantiate a given subprotocol on a - data channel, and whether it is signaled in-band using DCEP or out- - of-band using a non-DCEP protocol (or both). In particular, the SDP - offer generated by the RTCweb data channel stack includes no channel- - specific information. + Protocol (SCTP) [I-D.ietf-rtcweb-data-channel]. RTCWeb allows + applications to use data channels. RTCWeb defines an in-band Data + Channel Establishment Protocol (DCEP) + [I-D.ietf-rtcweb-data-protocol], however other in-band or out-of-band + protocols may be used for establishing data channels. Each data + channel consists of paired SCTP streams sharing the same SCTP Stream + Identifier. Data channels are created by endpoint applications + through the WebRTC API (Application Programming Interface), or other + users of a data channel like CLUE [I-D.ietf-clue-datachannel] They + can be used to transport proprietary or well-defined protocols, which + in the latter case can be signaled by the data channel "subprotocol" + parameter, conceptually similar to the WebSocket "subprotocol". + However, apart from the "subprotocol" value transmitted to the peer, + RTCWeb leaves it open how endpoint applications can agree on how to + instantiate a given subprotocol on a data channel, and whether it is + signaled in-band using DCEP or out-of-band using a non-DCEP protocol + (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 - establish data channels for transport of well-defined subprotocols, - to enable out-of-band negotiation. These procedures are based on - generic SDP offer/answer negotiation rules for SCTP based media - transport as specified in [I-D.ietf-mmusic-sctp-sdp] for the SDP "m" - line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. In the future, - data channels could be defined over other SCTP based protocols, such - as SCTP over IP. However, corresponding potential other "m" line - proto values are not considered in this document. + This document defines SDP offer/answer [RFC3264] negotiation + procedures to establish data channels for transport of well-defined + subprotocols, to enable out-of-band negotiation. These procedures + are based on generic SDP offer/answer negotiation rules for SCTP + based media transport as specified in [I-D.ietf-mmusic-sctp-sdp] for + the SDP "m" line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. In + the future, data channels could be defined over other SCTP based + protocols, such as SCTP over IP. However, corresponding potential + other "m=" line proto values are not considered in this document. This document makes use of MSRP (Message Session Relay Protocol) and BFCP (Binary Floor Control Protocol) in many of the examples. It does not provide a complete specification of how to negotiate the use of a data channel to transport MSRP. Procedures specific to each - subprotocol such as MSRP are documented elsewhere. The use of MSRP - in some examples is only to show how the generic procedures described - herein might apply to a specific subprotocol. + subprotocol would have to be documented elsewhere. For MSRP they are + documented in [I-D.ietf-mmusic-msrp-usage-data-channel] . The use of + MSRP in some examples is only to show how the generic procedures + described herein might apply to a specific subprotocol. 2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Terminology This document uses the following terms: @@ -233,64 +238,63 @@ Stream identifier: The identifier of the outbound and inbound SCTP streams composing a data channel. 4. Applicability Statement The mechanism in this document only applies to the Session Description Protocol (SDP) [RFC4566], when used together with the SDP offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of scope of this document, and is thus undefined. -5. SDP Offer/Answer Negotiation +5. SDP Data Channel attributes This section defines an SDP extension by which two clients can negotiate data channel-specific and subprotocol-specific parameters without using DCEP [I-D.ietf-rtcweb-data-protocol]. This SDP extension only defines usage in the context of SDP offer/answer. Appendix A provides information how data channels work in general and especially summarizes some key aspects, which should be considered 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 negotiation of data channels. The first attribute provides for negotiation of channel-specific parameters. The second attribute provides for negotiation of subprotocol-specific parameters. 5.1.1. SDP Attribute for Data Channel Parameter Negotiation - Associated with the SDP "m" line that defines the SCTP association - for data channels (defined in Section 3), each SDP offer and answer - includes one "a=dcmap:" attribute that defines the data channel - parameters for each data channel to be negotiated. Each such - attribute line specifies the following parameters for a data channel: - SCTP stream identifier, subprotocol, label, maximal number of - retransmissions, maximal retransmission time, order of delivery, and - priority. + This section defines a new media level attribute "a=dcmap:" that + defines the data channel parameters for each data channel to be + negotiated. The attribute specifies the following parameters for a + data channel: SCTP stream identifier, subprotocol, label, maximal + number of 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 - pairs of oppositely directed data channels having the same set of - attributes. It is assumed that the data channel properties - (reliable/partially reliable, ordered/unordered) are suitable per the - subprotocol transport requirements. + data channels as pairs of oppositely directed SCTP streams having the + same set of attributes. It is assumed that the data channel + properties (reliable/partially reliable, ordered/unordered) are + suitable per the subprotocol transport requirements. 5.1.1.1. dcmap Attribute "a=dcmap:" is a media level attribute having following ABNF (Augmented Backus-Naur Form, [RFC5234]) syntax. Formal Syntax: Name: dcmap + Value: dcmap-value Usage Level: media Charset Dependent: no Syntax: dcmap-value = dcmap-stream-id [ SP dcmap-opt *(";" dcmap-opt) ] @@ -343,35 +347,34 @@ which contains one non-printable 'escaped-char' character (the tabulator character). Within an 'a=dcmap:' attribute line's 'dcmap-opt' value either only one 'maxretr-opt' parameter or one 'maxtime-opt' parameter MAY be present. Both MUST NOT be present. 5.1.1.2. dcmap Multiplexing Category Multiplexing characteristics of SDP attributes are described in - [I-D.ietf-mmusic-sdp-mux-attributes]. Various SDP attribute - multiplexing categories are introduced there. + [I-D.ietf-mmusic-sdp-mux-attributes]. The multiplexing category of the "a=dcmap:" attribute is SPECIAL. 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 "a=dcmap:" attribute multiplexing rules are specified for the 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 multiple SCTP associations on top of a single DTLS association, or how to add multiple SCTP associations to one BUNDLE group, then multiplexing rules for the "a=dcmap:" attribute need to be defined as - well, for instance in an extension of this SDP based data channel - negotiation specification. + well, for instance in an extension of this SDP offer/answer based + data channel negotiation specification. 5.1.1.3. dcmap-stream-id Parameter The 'dcmap-stream-id' parameter indicates the SCTP stream identifier within the SCTP association used to form the data channel. 5.1.1.4. label Parameter The 'label' parameter indicates the name of the channel. It represents a label that can be used to distinguish, in the context of @@ -384,21 +387,21 @@ Note: The empty string MAY also be explicitly used as a 'label' value, such that 'label=""' is equivalent to the 'label' parameter 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. 5.1.1.5. subprotocol Parameter The 'subprotocol' parameter indicates which protocol the client expects to exchange via the channel. This parameter maps to the '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 'subprotocol' parameter is not present, then its value defaults to an empty string. Note: The empty string MAY also be explicitly used as 'subprotocol' value, such that 'subprotocol=""' is equivalent to the 'subprotocol' parameter not being present at all. [I-D.ietf-rtcweb-data-protocol] allows the DATA_CHANNEL_OPEN message's 'Subprotocol' value to be an empty string. @@ -440,39 +443,40 @@ The 'priority' parameter indicates the data channel's priority relative to the priorities of other data channels, which may additionally exist over the same SCTP association. The 'priority' parameter maps to the 'Priority' parameter defined in [I-D.ietf-rtcweb-data-protocol]. The 'priority' parameter is optional. In the absence of this parameter "priority=256" is assumed. 5.1.2. Other Media Level Attributes - In the SDP, each data channel declaration MAY also be followed by - other media level SDP attributes, which are either specifically - defined for or applied to the subprotocol in use. Each of these - attributes is represented by one new attribute line, and it includes - the contents of a media-level SDP attribute already defined for use - with this (sub)protocol in another IETF (Internet Engineering Task - Force) document. Subprotocol specific attributes MAY also be defined - for exclusive use with data channel transport, but MUST use the same - syntax described here for other subprotocol related attributes. + In the SDP media description, each data channel declaration MAY also + be followed by other media level SDP attributes, which are either + specifically defined for or applied to the subprotocol in use. Each + of these attributes is represented by one new attribute line, and it + includes the contents of a media-level SDP attribute already defined + for use with this (sub)protocol in another IETF (Internet Engineering + Task Force) document. Subprotocol specific attributes MAY also be + defined for exclusive use with data channel transport, but MUST use + the same syntax described here for other subprotocol related + attributes. 5.1.2.1. dcsa Attribute Each SDP attribute, related to the subprotocol, that would normally - be used to negotiate the subprotocol using SDP is replaced with an - attribute of the form "a=dcsa:stream-id original-attribute", where - dcsa stands for "data channel subprotocol attribute", stream-id is - the SCTP stream identifier assigned to this subprotocol instance, and - original-attribute represents the contents of the subprotocol related - attribute to be included. + be used to negotiate the subprotocol using SDP offer/answer is + replaced with an attribute of the form "a=dcsa:stream-id original- + attribute", where dcsa stands for "data channel subprotocol + attribute", stream-id is the SCTP stream identifier assigned to this + subprotocol instance, and original-attribute represents the contents + of the subprotocol related attribute to be included. The same syntax applies to any other SDP attribute required for negotiation of this instance of the subprotocol. Formal Syntax: Name: dcsa Value: dcsa-value @@ -514,71 +518,71 @@ attributes are used in the same way as defined in the original subprotocol specification, also if the subprotocol is transported over a data channel and if the attribute is correspondingly embedded in a "a=dcsa" attribute. There may be cases, where the usage of a subprotocol related media level attribute depends on the subprotocol's transport protocol. In such cases the subprotocol related usage of the attribute is expected to be described for the data channel transport. A data channel specific usage of a subprotocol attribute is expected to be specified - in the same document, that registers the subprotocol's identifier for - data channel usage as described in Section 8.1. + in the same document that registers the subprotocol's identifier for + data channel usage as described in Section 9.1. 5.1.2.2. dcsa Multiplexing Category The multiplexing category of the "a=dcsa:" attribute is SPECIAL. 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 "a=dcsa:" attribute multiplexing rules are specified for the 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 multiple SCTP associations on top of a single DTLS association, or how to add multiple SCTP associations to one BUNDLE group, then multiplexing rules for the "a=dcsa:" attribute need to be defined as well, for instance in an extension of this SDP based data channel 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 one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media description being accepted, and if this SDP offer/answer exchange results in the establishment of a new SCTP association, then the SDP offerer owns the even SCTP stream ids of this new SCTP association and the answerer owns the odd SCTP stream identifiers. If this "m" line is removed from the signaling session (its port number set to zero), and if usage of this or of a new UDP/DTLS/SCTP or TCP/DTLS/ SCTP based "m" line is renegotiated later on, then the even and odd SCTP stream identifier ownership is re-determined as described above. This document allows simultaneous use of SDP offer/answer and DCEP negotiation. However, an SCTP stream MUST NOT be referenced in a "a=dcmap:" or "a=dcsa:" attribute of an SDP offer/answer exchange if the associated SCTP stream has already been negotiated via DCEP. - Stream ids that are not currently used in SDP can be used for DCEP - negotiation. Stream id allocation per SDP offer/answer negotiation - may not align with DTLS role based allocation. This could cause - glare conditions when one side tries to do SDP offer/answer - negotiation on a stream id while the other end tries to open a data - channel on the same stream id using DCEP negotiation. To avoid these - glare conditions this document recommends that the data channel stack - user always selects stream ids per the above described SDP offer/ - answer rule even when DCEP negotiation is used. To avoid glare + Stream ids that are not currently used in SDP offer/answer can be + used for DCEP negotiation. Stream id allocation per SDP offer/answer + negotiation may not align with DTLS role based allocation. This + could cause glare conditions when one side tries to do SDP offer/ + answer negotiation on a stream id while the other end tries to open a + data channel on the same stream id using DCEP negotiation. To avoid + these glare conditions this document recommends that the data channel + stack user always selects stream ids per the 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 id allocation scheme, but such schemes are outside the scope of this document. -5.2.2. Negotiating Data Channel Parameters +6.2. Negotiating Data Channel Parameters Conveying a reliable data channel is achieved by including neither 'max-retr' nor 'max-time' in corresponding SDP offer's or answer's "a=dcmap:" attribute line. Conveying a partially reliable data channel is achieved by including only one of 'max-retr' or 'max- 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 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 answer contains both of these parameters then the offerer MUST treat @@ -589,95 +593,99 @@ The SDP answer SHALL echo the same subprotocol, max-retr, max-time, ordered parameters, if those were present in the offer, and MAY include a label parameter. They MAY appear in any order, which could be different from the SDP offer, in the SDP answer. When sending a subsequent offer or an answer, and for as long as the data channel is still open, the sender MUST replicate the same information. Data channel types defined in [I-D.ietf-rtcweb-data-protocol] are - mapped to SDP in the following manner, where "ordered=true" is the - default and may be omitted: + mapped to SDP media description in the following manner, where + "ordered=true" is the default and may be omitted: DATA_CHANNEL_RELIABLE ordered=true DATA_CHANNEL_RELIABLE_UNORDERED ordered=false DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT ordered=true;max-retr= DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED ordered=false;max-retr= DATA_CHANNEL_PARTIAL_RELIABLE_TIMED ordered=true;max-time= DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED ordered=false;max-time= -5.2.3. Opening a Data Channel +6.3. Generating initial Offer The procedure for opening a data channel using SDP offer/answer 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 with data channels that are to be SDP offer/answer negotiated, or loses an SDP offer glare resolution procedure in this case, it MUST wait until the ongoing SDP offer/answer completes before resuming the SDP offer/answer negotiation procedure. The agent that intends to send an SDP offer to create data channels through SDP offer/answer negotiation performs the following: 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 Determines the list of stream identifiers assigned to data channels opened through SDP offer/answer negotiation. o Completes the SDP offer with the "a=dcmap:" and "a=dcsa:" 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 add the subprotocol parameter to the "a=dcmap" attribute with a non-empty subprotocol identifier. o Sends the SDP offer. +6.4. Generating SDP answer + The peer receiving such an SDP offer performs the following: 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 determine whether to accept each offered data channel. o For accepted data channels, the agent MUST create peer instances for the data channels using the SCTP stream identifiers and channel parameters contained in the SDP offer. o Generates an SDP answer. o Completes the SDP answer with the "a=dcmap:" and optional "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. +6.5. Offerer Processing of the SDP Answer + 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 present in the SDP answer. o Applies the SDP answer. Each agent application MUST wait to send data until it has confirmation that the data channel at the peer is instantiated. For WebRTC, this is when both data channel stacks have channel parameters instantiated. This occurs: @@ -692,21 +700,21 @@ 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 association, when it receives the SDP answer confirming acceptance of the data channel or when it begins to receive data on the data channel from the peer, whichever occurs first. Note: DCEP is not used, that is neither the SDP offerer nor the SDP 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 negotiated via SDP offer/answer, the data channel stack always performs an SCTP SSN reset for this channel. It is specific to the subprotocol whether this closing MUST in 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 new SDP offer which excludes the "a=dcmap:" and "a=dcsa:" attribute @@ -745,21 +753,21 @@ 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 channel. This can only be done via new SDP offer/answer, describing the new subprotocol and its attributes, only after the corresponding data channel close acknowledgement is received from the peer (i.e. SCTP SSN reset of both incoming and outgoing streams is completed). This restriction is to avoid the race conditions between arrival of "SDP offer which reuses stream" with "SCTP SSN reset which closes 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. * Initial SDP offer: No data channel is negotiated yet. The DTLS association and SCTP association is negotiated and, if agreed, established as per [I-D.ietf-mmusic-sctp-sdp]. * Subsequent SDP offer: All the SDP offer/answer negotiated data channels are expected to be closed now. The DTLS/SCTP association remains open for SDP offer/answer or DCEP @@ -805,22 +813,21 @@ * The receiver of such an SDP offer or answer SHOULD ignore this entire "a=dcsa" attribute line. SDP offer or answer has an "a=dcsa" attribute, whose subprotocol attribute is known, but whose subprotocol attribute semantic is not known for the data channel transport case. * The receiver of such an SDP offer or answer SHOULD ignore this entire "a=dcsa" attribute line. -6. Examples - +7. Examples SDP offer: m=application 10001 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 192.0.2.1 a=max-message-size:100000 a=sctp-port:5000 a=setup:actpass a=fingerprint:SHA-1 \ 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB a=tls-id:abc3de65cddef001be82 @@ -918,27 +925,36 @@ Figure 3: Example 3 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 opens a new MSRP data channel with stream id 4. The answerer accepts the entire offer. As a result the offerer closes the earlier negotiated MSRP related data channel and both offerer and answerer may start using new the MSRP related data channel. -7. Security Considerations +8. Security Considerations - No security considerations are envisaged beyond those already - documented in [RFC4566]. + This document specifies new SDP attributes used in the negotiation of + the DATA channel parameters. -8. IANA Considerations -8.1. Subprotocol Identifiers + These parameter are negotiated as part of opening a SCTP channel over + 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 existing IANA "WebSocket Subprotocol Name Registry" table. The following text should be added following the title of the table. "This table also includes subprotocol identifiers specified for usage within a WebRTC data channel." The following reference should be added to under the heading @@ -951,128 +967,134 @@ "Subprotocol Definition" and "Reference" cells in the subprotocol's row of the IANA "WebSocket Subprotocol Name Registry" table should contain two entries. One entry in each of these cells should refer to the Websocket related subprotocol specification, and the other entry should refer to the data channel related subprotocol specification. NOTE to RFC Editor: Please replace "XXXX" with the number of this 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 RFC. This document defines a new SDP media-level attribute "a=dcmap:" as follows: +-----------------------+-------------------------------------------+ | Contact name: | MMUSIC Chairs | | Contact email: | mmusic-chairs@ietf.org | | Attribute name: | dcmap | | Attribute syntax: | As per Section 5.1.1.1 | | Attribute semantics: | As per Section 5.1.1.1 | | Usage level: | media | | Charset dependent: | No | | Purpose: | Define data channel specific parameters | | 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 | | Reference: | RFCXXXX | +-----------------------+-------------------------------------------+ -8.2.2. dcsa +9.2.2. dcsa NOTE to RFC Editor: Please replace "XXXX" with the number of this RFC. This document defines a new SDP media-level attribute "a=dcsa:" as follows: +-----------------------+-------------------------------------------+ | Contact name: | MMUSIC Chairs | | Contact email: | mmusic-chairs@ietf.org | | Attribute name: | dcsa | | Attribute syntax: | As per Section 5.1.2.1 | | Attribute semantics: | As per Section 5.1.2.1 | | Usage level: | media | | Charset dependent: | No | | Purpose: | Define data channel subprotocol specific | | | attributes | | 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 | | Reference: | RFCXXXX | +-----------------------+-------------------------------------------+ -8.3. New Usage Level +9.3. New Usage Level This document introduces a new "Data Channel Subprotocol Attribute" - (dcsa) usage level to the SDP to the IANA SDP att-field registry. - SDP attributes that are defined for use at the dcsa usage level only - SHALL use the dcsa usage level when registering the attribute. If - existing media attributes are used in a datachannel subprotocol - specific way (Section 5.1.2.1), then a new dcsa usage level MUST be - defined for the existing media attribute. Where the SDP attribute is - applicable to a particular subprotocol/s this SHALL also be - registered by indicating the applicable subprotocol identifiers (see - Section 8.1) along with the dcsa usage level. E.g. + (dcsa) usage level of the SDP media description to the IANA SDP att- + field registry. SDP attributes that are defined for use at the dcsa + usage level only SHALL use the dcsa usage level when registering the + attribute. If existing media attributes are used in a datachannel + subprotocol specific way (Section 5.1.2.1), then a new dcsa usage + level MUST be defined for the existing media attribute. Where the + SDP attribute is applicable to a particular subprotocol/s this SHALL + also be registered by indicating the applicable subprotocol + identifiers (see Section 9.1) along with the dcsa usage level. E.g. +-----------------------+-------------------------------------------+ | ... | ... | | Usage level: | dcsa(MSRP) | | ... | ... | +-----------------------+-------------------------------------------+ -9. Acknowledgments +10. Acknowledgments The authors wish to acknowledge the borrowing of ideas from other internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley and Gavin Llewellyn, and to thank Flemming Andreasen, Roni Even, Christian Groves, Gunnar Hellstrom, Christer Holmberg, Paul Kyzivat, Jonathan Lennox, Uwe Rauschenbach and Roman Shpount for their 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 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. -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 Add missing 'x' prefix to quoted-visible syntax. o Align SDP offerer and answerer handling when both max-retr and max-time are present. o Use of TEST-NET-1 ip addresses in examples. 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 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: * Replacement of the sentence "The RTCWeb working group has defined the concept of bi-directional data channels running on top of SCTP/DTLS (SCTP over the Datagram Transport Layer Security protocol)" with "The RTCWeb working group has defined the concept of bi-directional data channels running on top of the Stream Control Transmission Protocol (SCTP)". @@ -1086,69 +1108,69 @@ values are not considered in this document." o Replacement of "DTLS connection" with "DTLS association" throughout the document. 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 for this attribute for SCTP or SCTP/DTLS proto values". o In the text related to "Subsequent SDP answer" in section - Section 5.2.5 replacement of "The DTLS/SCTP association remains - open ..." with "The SCTP association remains open ...". + Section 6.7 replacement of "The DTLS/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 "... (after the SCTP association is set up)". o Addition of [I-D.ietf-mmusic-dtls-sdp] to the list of informative references. 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 as proposed on the MMUSIC list, https://www.ietf.org/mail- archive/web/mmusic/current/msg15827.html. 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. - 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 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. 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 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 in http://www.ietf.org/mail-archive/web/mmusic/current/ msg15357.html and http://www.ietf.org/mail- archive/web/mmusic/current/msg15359.html. -10.9. 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 "mmusic-chairs@ietf.org". o In Section 5.1.2.1 replacement of "Thus in the example above, the original attribute line "a=accept- types:text/plain" is represented by the attribute line "a=dcsa:2 accept-types:text/ plain", which specifies that this instance of MSRP being transported on the SCTP association using the data channel with stream id 2 accepts plain text files." with "... which specifies that this instance of the MSRP subprotocol being transported ...". @@ -1169,62 +1191,62 @@ 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 syntax definition of the "dcsa" attribute. 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 "a=dcsa:" attributes to "m" lines with proto values "UDP/DTLS/ 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 'subprotocol' parameter indicates which protocol the client expects to exchange via the channel. 'Subprotocol' is an optional parameter. If the 'subprotocol' parameter is not present, then its value defaults to the empty string." Replacement of this paragraph with following two paragraphs: * The 'subprotocol' parameter indicates which protocol the client expects to exchange via the channel. This parameter maps to 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 an optional parameter. If the 'subprotocol' parameter is not present, then its value defaults to the empty string. * Note: The empty string MAY also be explicitly used as 'subprotocol' value, such that 'subprotocol=""' is equivalent to the 'subprotocol' parameter not being present at all. [I-D.ietf-rtcweb-data-protocol] allows the DATA_CHANNEL_OPEN message's 'Subprotocol' value to be an empty string. o Addition of [I-D.ietf-mmusic-sdp-mux-attributes] to list the of normative references. o Addition of dcmap attribute specific IANA registration - Section 8.2.1. + Section 9.2.1. 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 dcmap SDP attribute. This section and the new "a=dcsa:" attribute related mux category section are similar to the "Mux Category" sections of the "a=sctp-port:" and "a=max-message-size:" attributes in [I-D.ietf-mmusic-sctp-sdp]. o Addition of new Section 5.1.2.2 describing the mux category of the 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 applications to use data channels and its in-band DCEP or out-of- 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 protocols for creating them". Additionally replacement of "In particular, the SDP offer generated by the application includes no channel-specific information" with "... generated by the RTCweb data channel stack includes no channel-specific information". @@ -1258,31 +1280,31 @@ [I-D.ietf-rtcweb-data-protocol]" with "The intention in exchanging these attributes is to create, on two peers, without use of DCEP [I-D.ietf-rtcweb-data-protocol], matched pairs of oppositely directed data channels having the same set of attributes". o In Section 5.1.1.6 replacement of "The 'max-retr' parameter indicates the maximal number a user message will be retransmitted" with "The 'max-retr' parameter indicates the maximal number of 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 already negotiated via DCEP" with "However, an SCTP stream MUST NOT be referenced in a dcmap or dcsa attribute of an SDP offer/ answer exchange if the associated SCTP stream has already been 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. -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 normative references to the list of informative references. Remover in -07 since not referenced 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 @@ -1299,50 +1321,50 @@ "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 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 offer/answer exchange MUST NOT be initiated if the associated SCTP stream is already negotiated via DCEP". - o In Section 5.2.2 replacement of sentence "By definition max-retr - and max-time are mutually exclusive, so only one of them can be + o In Section 6.2 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 5 of draft- 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 Addition of new Section 8.1 "Subprotocol identifiers" as - subsection of the "IANA Considerations" related Section 8. Also + o Addition of new Section 9.1 "Subprotocol identifiers" as + subsection of the "IANA Considerations" related Section 9. Also removal of the temporary note "To be completed. As [I-D.ietf- rtcweb-data-protocol] this document should refer to IANA's WebSocket Subprotocol Name Registry defined in [RFC6455]" - o In Section 5.2.2: + o In Section 6.2: * In the first paragraph replacement of the sentence "If an SDP offer contains both of these parameters then such an SDP offer will be rejected." with "If an SDP offer contains both of these parameters then the receiver of such an SDP offer MUST reject the SDP offer." * In the second paragraph capitalization of "shall" and "may" such that both sentences now read: "The SDP answer SHALL echo the same subprotocol, max-retr, max-time, ordered parameters, @@ -1351,35 +1373,35 @@ different from the SDP offer, in the SDP answer." * In the third paragraph replacement of the sentence "The same information MUST be replicated without changes in any subsequent offer or answer, as long as the data channel is still opened at the time of offer or answer generation." with "When sending a subsequent offer or an answer, and for as long as the data channel is still open, the sender MUST replicate the same information.". - o In Section 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 parameters were illustrated using example "a=dcmap" attribute lines. Replacement of these example "a=dcmap" attribute lines with just the "a=dcmap" attribute parameters being relevant for the channel type. - o In Section 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: No data channel negotiated yet." Replacement of this description with "Initial SDP offer: No data channel is negotiated yet. The DTLS connection and SCTP association is negotiated and, if agreed, established as per [I-D.ietf-mmusic-sctp-sdp]." - o In Section 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 externally negotiated data channels must be closed now." with "All the externally negotiated data channels are expected to be closed now.". o In Appendix A.2.2's sixth paragraph beginning with "[ASSUMPTION]" 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" there was a comment saying that "Either only maxretr-opt or @@ -1391,24 +1413,24 @@ NOT be present." o In Section 5.1.1.8 replacement of the first sentence "The 'ordered' parameter with value "true" indicates that DATA chunks in the channel MUST be dispatched to the upper layer by the receiver while preserving the order." with "The 'ordered' parameter with value "true" indicates that the receiver MUST dispatch DATA chunks in the data channel to the upper layer while preserving the order.". - o In Section 5.2.3's first paragraph replacement of the one - occurrence of "must" with "..., it MUST wait until ...". + o In Section 6.3's first paragraph replacement of the one occurrence + 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 this closing MUST in addition ..." * In the third paragraph replacement of the sentence "The port value for the "m" line SHOULD NOT be changed (e.g., to zero) when closing a data channel ..." with "The offerer SHOULD NOT change the port value for the "m" line (e.g., to zero) when closing a data channel ...". @@ -1420,21 +1442,21 @@ * In the last but one paragraph replacement of "must" with "The application MUST also close...". o In Section 5.1.2 addition of following note after the formal definition of the 'a=dcsa' attribute: "Note that the above reference to RFC 4566 defines were the attribute definition can be found; it does not provide any limitation on support of attributes defined in other documents in accordance with this attribute definition." -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 channel consisting of paired SCTP outbound and inbound streams." Replacement of this definition with "Data channel: A WebRTC data channel as specified in [I-D.ietf-rtcweb-data-channel]", and consistent usage of "data channel" in the remainder of the document including the document's headline." 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. @@ -1480,92 +1502,91 @@ rule with name "escaped" was defined. Renamed that rule's name to "escaped-char". o Insertion of a dedicated note right after the "a=dcmap:4" attribute example in Section 5.1.1.1 regarding the non-printable "escaped-char" character within the "label" value. o In Section 5.1.2's second paragraph replacement of "sctp stream 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 this document, the initial offerer based "SCTP over DTLS" owns by convention the even stream identifiers whereas the initial answerer owns the odd stream identifiers. This ownership is 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 initial offerer.' with 'If an SDP offer/answer exchange (could be the initial or a subsequent one) results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media description being accepted, and if this SDP offer/answer exchange results in the establishment of a new SCTP association, then the SDP offerer owns the even SCTP stream ids of this new SCTP association and the answerer owns the odd SCTP stream identifiers. If this "m" line is removed from the signaling session (its port number set to zero), and if usage of this or of a new UDP/DTLS/SCTP or TCP/DTLS/SCTP based "m" line is renegotiated later on, then the even and odd SCTP stream identifier ownership is redetermined as well as described above.' - o In Section 5.2.3 the first action of an SDP answerer, when - receiving an SDP offer, was described as "Applies the SDP offer. - Note that the browser ignores data channel specific attributes in - the SDP." Replacement of these two sentences with "Parses and - applies the SDP offer. Note that the typical parser normally - ignores unknown SDP attributes, which includes data channel - related attributes." + o In Section 6.3 the first action of an SDP answerer, when receiving + an SDP offer, was described as "Applies the SDP offer. Note that + the browser ignores data channel specific attributes in the SDP." + Replacement of these two sentences with "Parses and applies the + SDP offer. Note that the typical parser normally ignores unknown + SDP attributes, which includes data channel 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 with stream identifiers not "owned" by the agent.". Replacement of this sentence with "Note that the agent is asked to create data channels with SCTP stream identifiers contained in the SDP offer if the SDP offer is accepted." - o In Section 5.2.4 the third paragraph began with "A data channel - can be closed by sending a new SDP offer which excludes the dcmap - and dcsa attribute lines for the data channel. The port value for - the m line SHOULD NOT be changed (e.g., to zero) when closing a - data channel (unless all data channels are being closed and the - SCTP association is no longer needed), since this would close the - SCTP association and impact all of the data channels. If the - answerer accepts the SDP offer then it MUST also exclude the - corresponding attribute lines in the answer. ..." Replacement of - this part with "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 lines for the data channel. The port - value for the "m" line SHOULD NOT be changed (e.g., to zero) when - closing a data channel (unless all data channels are being closed - and the SCTP association is no longer needed), since this would - close the SCTP association and impact all of the data channels. - If the answerer accepts the SDP offer then it MUST close those - data channels whose "a=dcmap:" and "a=dcsa:" attribute lines were - excluded from the received SDP offer, unless those data channels - were already closed, and it MUST also exclude the corresponding - attribute lines in the answer." + o In Section 6.6 the third paragraph began with "A data channel can + be closed by sending a new SDP offer which excludes the dcmap and + dcsa attribute lines for the data channel. The port value for the + m line SHOULD NOT be changed (e.g., to zero) when closing a data + channel (unless all data channels are being closed and the SCTP + association is no longer needed), since this would close the SCTP + association and impact all of the data channels. If the answerer + accepts the SDP offer then it MUST also exclude the corresponding + attribute lines in the answer. ..." Replacement of this part with + "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 lines for the data channel. The port value for the "m" + line SHOULD NOT be changed (e.g., to zero) when closing a data + channel (unless all data channels are being closed and the SCTP + association is no longer needed), since this would close the SCTP + association and impact all of the data channels. If the answerer + accepts the SDP offer then it MUST close those data channels whose + "a=dcmap:" and "a=dcsa:" attribute lines were excluded from the + received SDP offer, unless those data channels were already + closed, and it MUST also exclude the corresponding attribute lines + 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 answer is not received, in which case the state of session should be kept per the last successful SDP offer/answer." Replacement of this sentence with "This delayed closure is RECOMMENDED in order 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 successful SDP offer/answer." o Although dedicated to "a=dcmap" and "a=dcsa" SDP syntax aspects Section 5.1.1 contained already procedural descriptions related to - data channel reliability negotiation. Creation of new - Section 5.2.2 and moval of reliability negotiation related text to - this new section. + data channel reliability negotiation. Creation of new Section 6.2 + and moval of reliability negotiation related text to this new + 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 parameter". As [I-D.ietf-rtcweb-data-protocol] this document should refer to IANA's WebSocket Subprotocol Name Registry defined in [RFC6455] o In whole document, replacement of "unreliable" with "partially reliable", which is used in [I-D.ietf-rtcweb-data-channel] and in [I-D.ietf-rtcweb-data-protocol] in most places. @@ -1601,53 +1622,53 @@ o In the "Examples" section, in the first two SDP offer examples in the a=dcmap attribute lines 'label="BGCP"' was replaced with 'label="BFCP"'. o In all examples, the "m" line proto value "DTLS/SCTP" was replaced with "UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were replaced with "a=max-message-size" attribute lines, as per draft- 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 Making subprotocol as an optional parameter in dcmap. o Specifying disallowed parameter combinations for max-time and max- retr. 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 negotiation and their usage. o Introduction of more generic terminology, e.g. "application" instead of "browser". o Clarification of how "max-retr and max-time affect the usage of unreliable and reliable WebRTC data channels. o Updates of examples to take into account the SDP syntax changes introduced with draft-ietf-mmusic-sctp-sdp-07. 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, and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP 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] Holmberg, C., Shpount, R., Loreto, S., and G. Camarillo, "Session Description Protocol (SDP) Offer/Answer Procedures For Stream Control Transmission Protocol (SCTP) over Datagram Transport Layer Security (DTLS) Transport.", draft-ietf-mmusic-sctp-sdp-26 (work in progress), April 2017. [I-D.ietf-mmusic-sdp-mux-attributes] @@ -1672,29 +1693,39 @@ [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, DOI 10.17487/RFC4566, July 2006, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . -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] Holmberg, C. and R. Shpount, "Session Description Protocol (SDP) Offer/Answer Considerations for Datagram Transport Layer Security (DTLS) and Transport Layer Security (TLS)", draft-ietf-mmusic-dtls-sdp-32 (work in progress), October 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] Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel Establishment Protocol", draft-ietf-rtcweb-data- protocol-09 (work in progress), January 2015. [IANA-SDP-Parameters] "Session Description Protocol (SDP) Parameters", Internet Assigned Numbers Authority Protocol Assignments Session Description Protocol (SDP) Parameters,