MMUSIC J. Recio, Ed.
Internet-Draft Unaffiliated
Updates: 4975 (if approved) C. Holmberg
Intended status: Standards Track Ericsson
Expires: January 1, 2021 June 30, 2020
MSRP over Data Channels
draft-ietf-mmusic-msrp-usage-data-channel-20
Abstract
This document specifies how the Message Session Relay Protocol (MSRP)
can be transported as a WebRTC data channel sub-protocol, using the
SDP offer/answer generic data channel negotiation framework to
establish such a channel. Two network configurations are supported:
connecting two MSRP over data channel endpoints; and a gateway
configuration, connecting an MSRP over data channel endpoint with an
MSRP over TCP or TLS endpoint. This document updates RFC4975.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 1, 2021.
Copyright Notice
Copyright (c) 2020 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
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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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
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. WebRTC Data Channel Considerations . . . . . . . . . . . . . 4
3.1. MSRP Data Channel . . . . . . . . . . . . . . . . . . . . 4
4. SDP Considerations . . . . . . . . . . . . . . . . . . . . . 5
4.1. MSRP URI . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. msrp-scheme . . . . . . . . . . . . . . . . . . . . . . . 5
4.3. Use of the dcmap Attribute . . . . . . . . . . . . . . . 5
4.4. Use of the dcsa Attribute . . . . . . . . . . . . . . . . 6
4.5. Use of the dcsa embedded setup Attribute . . . . . . . . 7
4.6. Session Closing . . . . . . . . . . . . . . . . . . . . . 7
4.7. Support for MSRP File Transfer Function . . . . . . . . . 8
4.8. Example SDP Negotiation . . . . . . . . . . . . . . . . . 8
5. MSRP Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. Session Mapping . . . . . . . . . . . . . . . . . . . . . 9
5.2. Session Opening . . . . . . . . . . . . . . . . . . . . . 9
5.3. Session Closing . . . . . . . . . . . . . . . . . . . . . 9
5.4. Data Framing . . . . . . . . . . . . . . . . . . . . . . 9
5.5. Data Sending, Receiving and Reporting . . . . . . . . . . 9
5.6. Support for MSRP File Transfer Function . . . . . . . . . 9
6. Gateway Considerations . . . . . . . . . . . . . . . . . . . 10
7. Updates to RFC4975 . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9.1. msrps URI scheme . . . . . . . . . . . . . . . . . . . . 11
9.2. Subprotocol Identifier MSRP . . . . . . . . . . . . . . . 11
9.3. SDP Attributes . . . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
11. CHANGE LOG . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-18' . . . . . . . . . . . . . . . . . . . . . . 18
11.2. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-17' . . . . . . . . . . . . . . . . . . . . . . 18
11.3. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-16' . . . . . . . . . . . . . . . . . . . . . . 18
11.4. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-15' . . . . . . . . . . . . . . . . . . . . . . 18
11.5. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-14' . . . . . . . . . . . . . . . . . . . . . . 18
11.6. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-13' . . . . . . . . . . . . . . . . . . . . . . 18
11.7. Changes against 'draft-ietf-mmusic-msrp-usage-data-
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channel-12' . . . . . . . . . . . . . . . . . . . . . . 19
11.8. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-11' . . . . . . . . . . . . . . . . . . . . . . 19
11.9. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-10' . . . . . . . . . . . . . . . . . . . . . . 19
11.10. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-09' . . . . . . . . . . . . . . . . . . . . . . 19
11.11. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-08' . . . . . . . . . . . . . . . . . . . . . . 19
11.12. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-07' . . . . . . . . . . . . . . . . . . . . . . 19
11.13. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-06' . . . . . . . . . . . . . . . . . . . . . . 20
11.14. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-05' . . . . . . . . . . . . . . . . . . . . . . 20
11.15. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-04' . . . . . . . . . . . . . . . . . . . . . . 20
11.16. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-03' . . . . . . . . . . . . . . . . . . . . . . 20
11.17. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-02' . . . . . . . . . . . . . . . . . . . . . . 20
11.18. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-01' . . . . . . . . . . . . . . . . . . . . . . 21
11.19. Changes against 'draft-ietf-mmusic-msrp-usage-data-
channel-00' . . . . . . . . . . . . . . . . . . . . . . 22
11.20. Changes against 'draft-ejzak-mmusic-msrp-usage-data-
channel-01' . . . . . . . . . . . . . . . . . . . . . . 23
11.21. Changes against '-00' . . . . . . . . . . . . . . . . . 23
12. Normative References . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
The Message Session Relay Protocol (MSRP) [RFC4975] is a protocol for
transmitting a series of related instant messages in the context of a
session. In addition to instant messaging, MSRP can also be used for
image sharing or file transfer. MSRP was initially defined in
[RFC4975] to work over TCP and TLS connections, and over a WebSocket
subprotocol specified by [RFC7977].
This document specifies the negotiation and transport of MSRP over a
WebRTC data channel [I-D.ietf-rtcweb-data-channel]. Negotiation is
carried out as specified in [I-D.ietf-mmusic-data-channel-sdpneg] and
MSRP is transported as a sub-protocol of a WebRTC data channel,
without the TCP and TLS layers.
Defining MSRP as a data channel sub-protocol has many benefits:
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o provides to applications a proven protocol enabling instant
messaging, file transfer, image sharing
o integrates those features with other WebRTC voice, video and data
features
o leverages the SDP-based negotiation already defined for MSRP
o allows the interworking with MSRP endpoints running on a TCP or
TLS connection
Compared to WebSockets, which provide a message passing protocol to
applications with no direct access to TCP or TLS sockets, data
channels provide a low latency transport, leverage NAT-aware
connectivity and security features of WebRTC, and are increasingly
available not only in modern browsers but in other applications that
use WebRTC for media or other purposes, such as IoT or telemetry in
general, non-media data exchange, and so on.
Considering an MSRP endpoint as an MSRP application that uses a
WebRTC data channel, this document describes two configurations where
the other endpoint is respectively either another MSRP over data
channel endpoint (e.g., a WebRTC application) or an MSRP endpoint
using either TCP or TLS transport.
This document updates [RFC4975] as described in Section 7.
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. WebRTC Data Channel Considerations
3.1. MSRP Data Channel
In this document, an MSRP data channel is a data channel for which
the instantiated sub-protocol is "msrp", and where the channel is
negotiated using the SDP-based external negotiation method defined in
[I-D.ietf-mmusic-data-channel-sdpneg].
The following WebRTC data channel property values
[I-D.ietf-rtcweb-data-channel] apply to an MSRP data channel:
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+--------------------------+------------------+
| Property | Value |
+--------------------------+------------------+
| Subprotocol Identifier | msrp |
| Transmission reliability | reliable |
| Transmission order | in-order |
| Label | See Section 4.3 |
+--------------------------+------------------+
4. SDP Considerations
This section describes the SDP considerations which are specific to
an MSRP data channel
4.1. MSRP URI
This document extends the MSRP URI syntax [RFC4975] by defining the
new transport parameter value "dc":
transport /= "dc"
; Add "dc" to existing transports per [RFC4975]
MSRP design provides for new transport bindings, see Section 6 of
[RFC4975], MSRP implementations are expected to allow unrecognized
transports for which there is no need to establish a connection to
the resource described by the URI, as it's the case of data channels
(Section 4.4).
4.2. msrp-scheme
The msrp-scheme portion of the MSRP-URI that represents an MSRP data
channel endpoint (used in the SDP path attribute and in the MSRP
message headers) is always "msrps", which indicates that the MSRP
data channel is always secured using DTLS as described in
[I-D.ietf-rtcweb-data-channel].
4.3. Use of the dcmap Attribute
An offerer and answerer SHALL, in each offer and answer, include a
dcmap attribute line ([I-D.ietf-mmusic-data-channel-sdpneg]) within
the media description of the SCTP association for each MSRP data
channel session to be negotiated.
The attribute includes the following data channel parameters:
o "label=" labelstring
o "subprotocol=" "msrp"
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The labelstring is set by the MSRP application according to
[I-D.ietf-mmusic-data-channel-sdpneg].
The offerer and answerer SHALL NOT include the max-retr and the max-
time attribute parameters in the dcmap attribute.
The offerer and answerer MAY include the ordered attribute parameter
in the dcmap attribute. If included, the attribute parameter value
SHALL be set to "true".
Below is an example of the dcmap attribute for an MSRP session to be
negotiated with stream-id=2 and label="chat":
a=dcmap:2 label="chat";subprotocol="msrp"
4.4. Use of the dcsa Attribute
An offerer and answerer SHALL, in each offer and answer, include a
dcsa attribute line ([I-D.ietf-mmusic-data-channel-sdpneg]) within
the media description for the SCTP association for each MSRP-specific
SDP attribute to be negotiated for each MSRP data channel being
negotiated.
An offerer and answerer SHALL include a dcsa attribute for each of
the following MSRP-specific SDP attributes:
o defined in [RFC4975]: "path".
o defined in [RFC6714]: "msrp-cema".
o defined in [RFC6135]: "setup". See Section 4.5
It is considered a protocol error if one or more of the dcsa embedded
attributes listed above are not included in an offer or answer.
An offerer and answerer MAY include a dcsa attribute for any of the
following MSRP-specific SDP attributes, following the procedures
defined for each attributes:
o defined in [RFC4975]: "accept-types", "accept-wrapped-types" and
"max-size"
o defined in [RFC4566]: "sendonly", "recvonly", "inactive" and
"sendrecv"
o defined in [RFC5547]: all the parameters related to MSRP file
transfer. See Section 4.7.
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A subsequent offer or answer MAY update the previously negotiated
MSRP subprotocol attributes while keeping the same subprotocol
a=dcmap description. The semantics for newly negotiated MSRP
subprotocol attributes are per [RFC4975].
When MSRP messages are transported on a data channel, the "path"
attribute is not used for routing of the messages. The MSRP data
channel is established using the SDP offer/answer procedures defined
in [I-D.ietf-mmusic-data-channel-sdpneg], and the MSRP messages are
then transported on that data channel. This is different from legacy
MSRP [RFC4975] but similar to MSRP CEMA [RFC6714]. However, when an
endpoint receives an MSRP message over a data channel, it MUST still
perform the MSRP-URI comparison procedures defined in [RFC4975].
4.5. Use of the dcsa embedded setup Attribute
As described in Section 4.4, the usage of a dsca embedded setup
attribute is mandated for MSRP sessions over data channels. It is
used to negotiate which MSRP session endpoint assumes the active role
as per Section 4.2.2 of [RFC6135] and Section 5.4 of [RFC4975]. It
has no relationship with the DTLS connection establishment roles
[I-D.ietf-mmusic-sctp-sdp].
The dcsa embedded setup attribute is of the form "a=dcsa:x
setup:<role>", with x being the data channel's SCTP stream
identifier, so that such attribute is explicitly associated with an
MSRP session over a specific data channel.
4.6. Session Closing
An MSRP session is closed by closing the associated data channel,
following the procedures in [I-D.ietf-mmusic-data-channel-sdpneg].
The port value for the "m=" line SHOULD NOT be changed (e.g. to zero)
when closing an MSRP session (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.
In all cases in [RFC4975] where the procedure calls for setting the
port to zero for the MSRP "m=" line in an SDP offer for TCP
transport, the SDP offerer of an MSRP session with data channel
transport SHALL remove the corresponding dcmap and dcsa attributes.
The SDP answerer must ensure that no dcmap or dcsa attributes are
present in the SDP answer if no corresponding attributes are present
in the received SDP offer.
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4.7. Support for MSRP File Transfer Function
SDP attributes specified in [RFC5547] for a file transfer "m=" line
are embedded as subprotocol-specific attributes using the syntax
defined in [I-D.ietf-mmusic-data-channel-sdpneg].
4.8. Example SDP Negotiation
The following is an example of an "m=" line for data channels in an
SDP offer that includes the attributes needed to establish two MSRP
sessions: one for chat and one for file transfer. The example is
derived from a combination of examples in [RFC4975] and [RFC5547].
m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 198.51.100.79
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:4a756565cddef001be82
a=dcmap:0 label="chat";subprotocol="msrp"
a=dcsa:0 msrp-cema
a=dcsa:0 setup:active
a=dcsa:0 accept-types:message/cpim text/plain
a=dcsa:0 path:msrps://198.51.100.79:54111/si438dsaodes;dc
a=dcmap:2 label="file transfer";subprotocol="msrp"
a=dcsa:2 sendonly
a=dcsa:2 msrp-cema
a=dcsa:2 setup:active
a=dcsa:2 accept-types:message/cpim
a=dcsa:2 accept-wrapped-types:*
a=dcsa:2 path:msrps://198.51.100.79:54111/jshA7we;dc
a=dcsa:2 file-selector:name:"picture1.jpg" \
type:image/jpeg size:1463440 hash:sha-1:\
FF:27:0D:81:14:F1:8A:C3:35:3B:36:64:2A:62:C9:3E:D3:6B:51:B4
a=dcsa:2 file-transfer-id:rjEtHAcYVZ7xKwGYpGGwyn5gqsSaU7Ep
a=dcsa:2 file-disposition:attachment
a=dcsa:2 file-date:creation:"Mon, 12 Jan 2018 15:01:31 +0800"
a=dcsa:2 file-icon:cid:id2@bob.example.com
a=dcsa:2 file-range:1-1463440
5. MSRP Considerations
The procedures specified in [RFC4975] apply except when this document
specifies otherwise. This section describes the MSRP considerations
specific to an MSRP data channel.
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5.1. Session Mapping
In this document, each MSRP session maps to one data channel exactly.
5.2. Session Opening
Section 4.5 describes how the active MSRP session endpoint role is
negotiated. The active MSRP session endpoint uses the data channel
established for this MSRP session by the generic data channel opening
procedure defined in [I-D.ietf-mmusic-data-channel-sdpneg].
As soon as the WebRTC data channel is opened, the MSRP session is
actually opened by the active MSRP session endpoint. In order to do
this the active MSRP endpoint sends an MSRP SEND message (empty or
not) to the other MSRP endpoint.
5.3. Session Closing
The closure of an MSRP session SHALL be signaled via SDP following
the requirements in Section 4.6
If the data channel used to transport the MSRP session fails and gets
torn down, the endpoints SHALL consider the MSRP session failed. An
MSRP endpoint MAY, based on local policy, try to negotiate a new MSRP
data channel.
5.4. Data Framing
Each text-based MSRP message is sent on the corresponding SCTP stream
using standard MSRP framing and chunking procedures, as defined in
[RFC4975], with each MSRP chunk delivered in a single SCTP user
message. Therefore all sent MSRP chunks including the MSRP chunk
header SHALL have lengths of less than or equal to the value of the
peer's "a=max-message-size" attribute, which is associated with the
data channel's SCTP association.
5.5. Data Sending, Receiving and Reporting
Data sending, receiving and reporting procedures SHALL conform to
[RFC4975].
5.6. Support for MSRP File Transfer Function
[RFC5547] defines an end-to-end file transfer method based on MSRP
and the SDP offer/answer mechanism. This file transfer method is
also usable by MSRP endpoints using data channels, with the following
considerations:
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o As an MSRP session maps to one data channel, a file transfer
session maps also to one data channel.
o SDP attributes are negotiated as specified in Section 4.7.
o Once the file transfer is complete, the same data channel MAY be
reused for another file transfer.
6. Gateway Considerations
This section describes the network configuration where one MSRP
endpoint uses an MSRP data channel as MSRP transport, the other MSRP
endpoint uses TLS/TCP connections as MSRP transport, and the two MSRP
endpoints interwork via a gateway.
Specifically, a gateway can be configured to interwork an MSRP
session over a data channel with a peer that does not support data
channel transport in one of two ways.
In one model, the gateway performs as an MSRP B2BUA to interwork all
the procedures as necessary between the endpoints. No further
specification is needed for this model.
Alternately, the gateway can provide transport level interworking
between MSRP endpoints using different transport protocols. In
accordance with Section 4.4, path attributes SHALL NOT be used for
transport level interworking.
When the gateway performs transport level interworking between MSRP
endpoints, all of the procedures in Section 5 and Section 4 apply to
each peer, with the following additions:
o The gateway SHALL use CEMA towards the non-data channel endpoint.
o If the non-data channel endpoint does not support CEMA, transport
level interworking mode is not possible, the gateway needs to act
as an MSRP B2BUA.
o The gateway SHALL NOT modify the path attribute received from data
channel or from non-data channel endpoints.
o The gateway SHALL NOT modify the setup value received from data
channel or from non-data channel endpoints.
o The endpoint establishing an MSRP session using data channel
transport SHALL NOT request inclusion of any relays, although it
MAY interoperate with a peer that signals the use of relays.
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7. Updates to RFC4975
This document updates [RFC4975], by allowing the usage of the "msrps"
scheme when the underlying connection is protected with DTLS.
8. Security Considerations
MSRP traffic over data channels is secured, including
confidentiality, integrity and source authentication, as specified by
[I-D.ietf-rtcweb-data-channel]
Note that discussion in [RFC4975] on MSRP message attribution to
remote identities applies to data channel transport.
9. IANA Considerations
NOTE to RFC Editor: Please replace all instances of all instances of
RFCXXXX with the number of this RFC.
9.1. msrps URI scheme
This document modifies the usage of the msrps URI scheme, registered
by [RFC4975], adding DTLS as a protected transport indicated by the
URI scheme.
A reference to RFCXXXX is added to the URI scheme "msrps" in the
Uniform Resource Identifier (URI) Schemes Registry.
9.2. Subprotocol Identifier MSRP
This document adds a reference to the subprotocol identifier "msrp"
in the "WebSocket Subprotocol Name Registry"
9.3. SDP Attributes
This document modifies the usage of the SDP setup attribute, if this
attribute is included in an SDP 'dcsa' attribute associated to an
MSRP data channel. The modified usage is described in Section 4.5.
This document also adds a reference to the following attributes in
the Session Description Protocol (SDP) Parameters registry, if these
attributes are included in SDP 'dcsa' attributes associated to an
MSRP data channel. Usage of these attributes is described in section
Section 4.4:
o "path"
o "msrp-cema"
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o "accept-types"
o "accept-wrapped-types"
o "max-size"
o "sendonly"
o "recvonly"
o "inactive"
o "sendrecv"
o "file-selector"
o "file-transfer-id"
o "file-disposition"
o "file-date"
o "file-icon"
o "file-range"
The usage level "dcsa(msrp)" is added to the registration of the SDP
'setup' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | setup |
| Usage level: | dcsa(msrp) |
| Purpose: | Negotiate the active role of an MSRP |
| | session over a data channel as per |
| | Section 4.5 |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'path' attribute in the Session Description Protocol (SDP) Parameters
registry as follows:
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+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | path |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate an endpoint, but not used for |
| | routing, as described in Section 4.4 |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'msrp-cema' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | msrp-cema |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate that the routing of MSRP |
| | messages transported on a data channel is |
| | more similar to the MSRP CEMA mechanism |
| | than the legacy MSRP routing mechanism. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'accept-types' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | accept-types |
| Usage level: | dcsa(msrp) |
| Purpose: | Contain the list of media types that the |
| | endpoint is willing to receive. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'accept-wrapped-types' attribute in the Session Description Protocol
(SDP) Parameters registry as follows:
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+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | accept-wrapped-types |
| Usage level: | dcsa(msrp) |
| Purpose: | Contain the list of media types that the |
| | endpoint is willing to receive in an MSRP |
| | message with multipart content. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'max-size' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | max-size |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate the largest message an MSRP |
| | endpoint wishes to accept. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'sendonly' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | sendonly |
| Usage level: | dcsa(msrp) |
| Purpose: | Negotiate the direction of the media flow |
| | on an MSRP data channel. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'recvonly' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
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+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | recvonly |
| Usage level: | dcsa(msrp) |
| Purpose: | Negotiate the direction of the media flow |
| | on an MSRP data channel. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'inactive' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | inactive |
| Usage level: | dcsa(msrp) |
| Purpose: | Negotiate the direction of the media flow |
| | on an MSRP data channel. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'sendrecv' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | sendrecv |
| Usage level: | dcsa(msrp) |
| Purpose: | Negotiate the direction of the media flow |
| | on an MSRP data channel. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-selector' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
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+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-selector |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate a file in an MSRP file transfer |
| | negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-transfer-id' attribute in the Session Description Protocol
(SDP) Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-transfer-id |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate a unique identifier of the file |
| | transfer operation in an MSRP file |
| | transfer negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-disposition' attribute in the Session Description Protocol
(SDP) Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-disposition |
| Usage level: | dcsa(msrp) |
| Purpose: | Provide a suggestion to the other |
| | endpoint about the intended disposition |
| | of the file in an MSRP file transfer |
| | negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-date' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
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+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-date |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate a date related to the file in an |
| | MSRP file transfer negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-icon' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-icon |
| Usage level: | dcsa(msrp) |
| Purpose: | Contain a pointer to a small preview icon |
| | representing the contents of the file in |
| | an MSRP file transfer negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
The usage level "dcsa(msrp)" is added to the registration of the SDP
'file-range' attribute in the Session Description Protocol (SDP)
Parameters registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-range |
| Usage level: | dcsa(msrp) |
| Purpose: | Contain the range of transferred octets |
| | of the file in an MSRP file transfer |
| | negotiation. |
| Reference: | RFCXXXX |
+-----------------------+-------------------------------------------+
10. Acknowledgments
The authors wish to acknowledge the borrowing of ideas from another
internet draft by Peter Dunkley and Gavin Llewellyn, and to thank
Flemming Andreasen, Christian Groves, Paul Kyzivat, Jonathan Lennox,
Uwe Rauschenbach, Albrecht Schwarz, and Keith Drage for their
invaluable comments.
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Richard Ejzak, Keith Drage and Juergen Stoetzer-Bradler contributed
an earlier version, before the draft was re-adopted.
Julien Maisonneuve helped with the re-adoption of the draft, and
Maridi R. Makaraju (Raju) contributed valuable comments after the
draft was re-adopted.
11. CHANGE LOG
11.1. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-18'
o Fix error in purpose of dcsa(marp) entry for 'path' attribute.
11.2. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-17'
o Shepherd's review: update to the file header, remove reference in
abstract, mention update on introduction, reorder and complete
IANA considerations.
o Editorial: a MSRP -> an MSRP; MSRP -> msrp for consistency; typos.
11.3. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-16'
o WGLC review: draft updates RFC4975; clarify introduction; rewrite
wording on path and transport negotiation; session closing
clarifications; references cleanup.
o Editorial: consistent SHALL usage; reorder updates, security and
IANA sections for consistency; typos; acknowledgements.
11.4. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-15'
o More concise and clear introduction and section descriptions.
o Updates on author list, contributions and acknowledgements.
11.5. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-14'
o Reorganization following t140-usage-data-channel structure.
11.6. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-13'
o Clarify gateway procedures in accordance to mandatory use of CEMA.
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11.7. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-12'
o Make CEMA mandatory, clarify SDP procedures.
11.8. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-11'
o Additional clarifications on cema and path attribute after mail
list feedback.
11.9. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-10'
o Corrections and clarifications on cema and path attributes after
mail list feedback.
11.10. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-09'
o Corrected area to ART.
11.11. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-08'
o Updated reference to 4566bis.
o Expanded motivation paragraphs in introduction.
11.12. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-07'
o Move security considerations after IANA considerations, following
RFC7322 suggested order.
o Update references to use xml.resource.org citation database.
o Reformat of the section discussing setup parameter
o Align examples with latest [I-D.ietf-mmusic-data-channel-sdpneg]
draft.
o Edit section 6 for clarity.
o Security requirements.
o Clarify comment on unrecognized transports and session opening.
o Update year, add editor.
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11.13. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-06'
o Modification of Keith's address information.
11.14. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-05'
o Modification of Juergen's address information.
11.15. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-04'
o Addition of "I-D.ietf-mmusic-rfc4566bis"/> to list of normative
references.
o Addition of IANA considerations for setup attribute as per section
8.2.4 of "I-D.ietf-mmusic-rfc4566bis"/>.
11.16. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-03'
o Addition of IANA registration related Section 9.2.
11.17. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-02'
o Addition of "a=setup:actpass", "a=connection:new",
"a=fingerprint:..." and "a=dcsa:x setup=active" SDP attributes to
the SDP example in Section 4.8.
o Addition of "RFC4145" and [I-D.ietf-mmusic-sctp-sdp] to list of
normative references.
o Addition of new Section 4.5 describing how the active MSRP session
endpoint role is negotiated.
o Extension of first paragraph of session-opening with new first
sentence "Section 4.5 describes how the active MSRP session
endpoint role is negotiated.".
o First sentence of second paragraph in session-opening was "As soon
as this data channel is opened, the MSRP session is actually
opened by the active MSRP endpoint which sends an MSRP SEND
message (empty or not) to the other MSRP endpoint." Replacement
of this sentence with "As soon as this data channel is opened, the
MSRP session is actually opened by the active MSRP endpoint. In
order to do this the active MSRP endpoint sends an MSRP SEND
message (empty or not) to the other MSRP endpoint."
o Addition of setup attribute specific behavior descriptions of data
channel to TCP or TLS interworking gateways in Section 6.
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11.18. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-01'
o In the abstract replacement of the first sentence "This document
specifies how the Message Session Relay Protocol (MSRP) can be
instantiated as a data channel sub-protocol, using the SDP offer/
answer exchange-based external negotiation defined in
[I-D.ietf-mmusic-data-channel-sdpneg]" with "This document
specifies how the Message Session Relay Protocol (MSRP) can be
instantiated as a data channel sub-protocol, using the SDP offer/
answer exchange-based generic data channel negotiation framework"
in order to remove the reference from the abstract text.
o Addition of following sentence to the second paragraph in
Section 1: "The MSRP protocol negotiation defined in this document
is based on the generic SDP offer/answer exchange based data
channel negotiation as specified in
[I-D.ietf-mmusic-data-channel-sdpneg]".
o In Section 3.1 replacement of sub-protocol identifier "msrp" with
"MSRP" in order to make this consistent with the formal
specification in Section 4.3.
o Throughout the text replacement of "shall" with "SHALL" etc where
appropriate as per [RFC2119].
o In Section 4.3 replacement of sentence 'The max-retr, max-time and
ordered parameters shall not be used.' with 'Ordered and reliable
data channels MUST always be used, such that the "max-retr" and
"max-time" parameters SHALL NOT be used. If the "ordered"
parameter is used, then its value MUST be equal to "true".'.
o In Section 4.3 removal of "(on default SCTP port 5000)" from the
sentence preceding the example "a=dcmap" attribute line.
o In Section 4.4 first paragraph was "The SDP offer shall also
include a dcsa attribute line (defined in
[I-D.ietf-mmusic-data-channel-sdpneg]) within the media
description for the SCTP association for each MSRP-specific SDP
attribute to be negotiated for each MSRP data channel being
negotiated.". Replacement of this paragraph with "The SDP offer
SHALL also include within the media description for the SCTP
association a dcsa attribute line (defined in
[I-D.ietf-mmusic-data-channel-sdpneg]) for each MSRP-specific SDP
attribute to be negotiated for each MSRP data channel being
negotiated.".
o Appended following sentence at the end of the first paragraph of
Section 5.4: "Therefore all sent MSRP chunks MUST have lengths of
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less than or equal to the value of the peer's "a=max-message-size"
attribute, which is associated with the data channel's SCTP
association.".
o Addition of the previously missing colon to the "a=sctp-port"
attribute line in Section 4.8.
o In Section 5.3 replacement of the first paragraph "Closing of an
MSRP session is done using the generic data channel closing
procedure defined in [I-D.ietf-mmusic-data-channel-sdpneg]." with
'The closure of an MSRP session MUST be signaled via an SDP offer/
answer exchange which removes the "a=dcmap:" and "a=dcsa:"
attribute lines associated with the MSRP session from the
associated DTLS/SCTP based media description. This results in the
associated data channel being closed as well as per
[I-D.ietf-mmusic-data-channel-sdpneg], where the actual data
channel closure procedure is typically initiated by the SDP
answerer right after having accepted the SDP offer.'.
11.19. Changes against 'draft-ietf-mmusic-msrp-usage-data-channel-00'
o Additional reference to [I-D.ietf-mmusic-data-channel-sdpneg] in
list of normative references.
o Replacement of previous document title "MSRP over SCTP/DTLS data
channels" with "MSRP over Data Channels" in order to align with
the terminology used in [I-D.ietf-mmusic-data-channel-sdpneg].
o In "terminology", "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 either
"data channel" or "MSRP data channel" in the remainder of the
document."
o In the introduction replacement of references to
[I-D.ietf-rtcweb-data-protocol] with a reference to
[I-D.ietf-rtcweb-data-channel].
o Consistent usage of '"m=" line' in whole document as per
[RFC4566].
o In the gateway configuration section (Section 6) replacement of
the first sentence "This section describes the network
configuration where one endpoint runs MSRP over a WebRTC SCTP/DTLS
connection, the other MSRP endpoint runs MSRP over one or more
TLS/TCP connections, and the two endpoints interwork via an MSRP
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gateway" with "This section describes the network configuration
where one MSRP endpoint uses data channels as MSRP transport, the
other MSRP endpoint uses TLS/TCP connections as MSRP transport,
and the two MSRP endpoints interwork via an MSRP gateway".
11.20. Changes against 'draft-ejzak-mmusic-msrp-usage-data-channel-01'
o Removed empty spaces after ";" in the examples' "a=dcmap"
attribute lines.
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.
11.21. Changes against '-00'
o Transport parameter change for MSRP to allow MSRP RFC transports.
o Clarification on SDP offer/answer and removing duplicated
procedures and refer them to draft-ejzak-mmusic-data-channel-
sdpneg-02.
12. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-13 (work in
progress), January 2015.
[I-D.ietf-mmusic-data-channel-sdpneg]
Drage, K., Makaraju, M., Ejzak, R., Marcon, J., and R.
Even, "SDP-based Data Channel Negotiation", draft-ietf-
mmusic-data-channel-sdpneg-28 (work in progress), May
2019.
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[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.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
"The Message Session Relay Protocol (MSRP)", RFC 4975,
DOI 10.17487/RFC4975, September 2007,
<https://www.rfc-editor.org/info/rfc4975>.
[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
and P. Kyzivat, "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
DOI 10.17487/RFC5547, May 2009,
<https://www.rfc-editor.org/info/rfc5547>.
[RFC6135] Holmberg, C. and S. Blau, "An Alternative Connection Model
for the Message Session Relay Protocol (MSRP)", RFC 6135,
DOI 10.17487/RFC6135, February 2011,
<https://www.rfc-editor.org/info/rfc6135>.
[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message
Session Relay Protocol (MSRP)", RFC 6714,
DOI 10.17487/RFC6714, August 2012,
<https://www.rfc-editor.org/info/rfc6714>.
[RFC7977] Dunkley, P., Llewellyn, G., Pascual, V., Salgueiro, G.,
and R. Ravindranath, "The WebSocket Protocol as a
Transport for the Message Session Relay Protocol (MSRP)",
RFC 7977, DOI 10.17487/RFC7977, September 2016,
<https://www.rfc-editor.org/info/rfc7977>.
Authors' Addresses
Jose M. Recio (editor)
Unaffiliated
Email: jose@ch3m4.com
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Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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