Internet DRAFT - draft-ietf-mmusic-msrp-usage-data-channel
draft-ietf-mmusic-msrp-usage-data-channel
MMUSIC J. Recio, Ed.
Internet-Draft Unaffiliated
Updates: 4975 (if approved) C. Holmberg
Intended status: Standards Track Ericsson
Expires: February 19, 2021 August 18, 2020
MSRP over Data Channels
draft-ietf-mmusic-msrp-usage-data-channel-24
Abstract
This document specifies how a Web Real-Time Communication (WebRTC)
data channel can be used as a transport mechanism for the Message
Session Relay Protocol (MSRP) and how the Session Description
Protocol (SDP) offer/answer mechanism can be used to negotiate such a
data channel, referred to as an MSRP data channel. Two network
configurations are supported: connecting two MSRP data channel
endpoints; and a gateway configuration, connecting an MSRP data
channel endpoint with an MSRP over TCP or TLS endpoint. This
document updates RFC4975. 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 February 19, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. WebRTC Data Channel Considerations . . . . . . . . . . . . . 4
3.1. MSRP Data Channel . . . . . . . . . . . . . . . . . . . . 4
4. SDP Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. MSRP URI . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. msrp-scheme . . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Use of the dcmap Attribute . . . . . . . . . . . . . . . 5
4.4. Use of the dcsa Attribute . . . . . . . . . . . . . . . . 5
4.5. Use of the dcsa embedded setup Attribute . . . . . . . . 6
4.6. Session Closing . . . . . . . . . . . . . . . . . . . . . 7
4.7. Support for MSRP File Transfer Function . . . . . . . . . 7
4.8. Example . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. MSRP Considerations . . . . . . . . . . . . . . . . . . . . . 9
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 . . . . . . . . . 10
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 . . . . . . . . . . . . . . . 12
9.3. SDP Attributes . . . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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
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[RFC4975] to work over TCP and TLS connections, and over a WebSocket
subprotocol specified by [RFC7977].
This document specifies how a Web Real-Time Communication (WebRTC)
data channel [I-D.ietf-rtcweb-data-channel] can be used as a
transport mechanism for MSRP, without the TCP and TLS layers, and how
the Session Description Protocol (SDP) offer/answer mechanism for
data channels [I-D.ietf-mmusic-data-channel-sdpneg] can be used to
negotiate such a data channel.
In this document, an MSRP data channel refers to a WebRTC data
channel for which the instantiated subprotocol is "msrp" and where
the data channel is negotiated using the SDP offer/answer mechanism
[I-D.ietf-mmusic-data-channel-sdpneg].
Defining MSRP as a data channel subprotocol has many benefits:
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.
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", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. WebRTC Data Channel Considerations
3.1. MSRP Data Channel
The following WebRTC data channel property values
[I-D.ietf-rtcweb-data-channel] apply to an MSRP data channel:
+--------------------------+------------------+
| Property | Value |
+--------------------------+------------------+
| Subprotocol Identifier | msrp |
| Transmission reliability | reliable |
| Transmission order | in-order |
| Label | See Section 4.3 |
+--------------------------+------------------+
4. SDP Considerations
The generic SDP considerations, including the SDP offer/answer
procedures [RFC3264], for negotiating a WebRTC data channel are
defined in [I-D.ietf-mmusic-data-channel-sdpneg]. This section, and
its subsections, define the SDP considerations that are specific to
an MSRP data channel, identified by the 'subprotocol' attribute
parameter, with a "msrp" parameter value, in the 'dcmap' attribute.
4.1. MSRP URI
This document extends the MSRP URI syntax [RFC4975] by defining the
new transport parameter value "dc" (an abbreviation of data channel):
transport /= "dc"
; Add "dc" to existing transports per Section 9 of [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].
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4.3. Use of the dcmap Attribute
An offerer and answerer SHALL, in each offer and answer, include a
'dcmap' attribute [I-D.ietf-mmusic-data-channel-sdpneg] in the SDP
media description (m= section) [RFC4566] describing the SCTP
association [RFC4960] used to realize the MSRP data channel.
The attribute includes the following data channel parameters:
o "label=" labelstring
o "subprotocol=" "msrp"
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 a '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 can, in each offer and answer, include one or
more 'dcsa' attributes [I-D.ietf-mmusic-data-channel-sdpneg] in the
m= section describing the SCTP association used to realize the MSPR
data channel. An SDP attribute included in a 'dcsa' attribute is
referred to as a dcsa embedded attribute.
If an offerer or answerer receives a 'dcsa' attribute that contains
an SDP attribute which usage has not been defined for an MSRP data
channel, the offerer or answerer should ignore the 'dcsa' attribute,
following the rules in Section 6.7 of
[I-D.ietf-mmusic-data-channel-sdpneg].
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".
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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 attribute:
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.
A subsequent offer or answer MAY update the previously negotiated
MSRP subprotocol attributes while keeping the 'dcmap' attribute
associated with the MSRP data channel unchanged. 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]. Because of this,
a dcsa embedded 'msrp-cema' attribute is mandated for MSRP sessions
over data channels. 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.
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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.
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
Below is an example of an offer and an answer that include 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].
Offer:
m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP6 2001:db8::3
a=max-message-size:100000
a=sctp-port:5000
a=setup:actpass
a=fingerprint:SHA-256 12:DF:3E:5D:49:6B:19:E5:7C:AB:4A:AD:B9:B1:3F:\
82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB:4A:AD
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://2001:db8::3:54111/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:*
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a=dcsa:2 path:msrps://2001:db8::3:54111/jshA7we;dc
a=dcsa:2 file-selector:name:"picture1.jpg" type:image/jpeg \
size:1463440 hash:sha-256:7C:DF:3E:5D:49:6B:19:E5:12:AB:4A:AD: \
4A:B1:3F:82:3E:3B:54:12:02:5D:18:DF:49:6B:19:E5:7C:AB:B9:AD
a=dcsa:2 file-transfer-id:rjEtHAcYVZ7xKwGYpGGwyn5gqsSaU7Ep
a=dcsa:2 file-disposition:attachment
a=dcsa:2 file-date:creation:"Tue, 11 Aug 2020 19:05:30 +0200"
a=dcsa:2 file-icon:cid:id2@bob.example.com
a=dcsa:2 file-range:1-1463440
Answer:
m=application 51444 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP6 IP6 2001:db8::1
a=max-message-size:100000
a=sctp-port:6000
a=setup:passive
a=fingerprint:SHA-256 5D:02:3E:AD:49:6B:19:E5:7C:AB:4A:AD:B9:B1: \
3F:82:18:3B:54:DF:12:6B:3E:5D:49:DF:19:E5:7C:AB:4A:5D
a=tls-id:65cd4a7565debe82f100
a=dcmap:0 label="chat";subprotocol="msrp"
a=dcsa:0 msrp-cema
a=dcsa:0 setup:passive
a=dcsa:0 accept-types:message/cpim text/plain
a=dcsa:0 path:msrps://2001:db8::1:51444/di551fsaodes;dc
a=dcmap:2 label="file transfer";subprotocol="msrp"
a=dcsa:2 recvonly
a=dcsa:2 msrp-cema
a=dcsa:2 setup:passive
a=dcsa:2 accept-types:message/cpim
a=dcsa:2 accept-wrapped-types:*
a=dcsa:2 path:msrps://2001:db8::1:51444/jksh7Bwc;dc
a=dcsa:2 file-selector:name:"picture1.jpg" type:image/jpeg \
size:1463440
a=dcsa:2 file-transfer-id:rjEtHAcYVZ7xKwGYpGGwyn5gqsSaU7Ep
a=dcsa:2 file-range:1-1463440
Note that due to RFC formatting conventions, this document splits SDP
across lines whose content would exceed 72 characters. A backslash
character marks where this line folding has taken place. This
backslash and its trailing CRLF and whitespace would not appear in
actual SDP content.
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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.
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 peer (passive) 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 data
channel 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 SHALL have lengths of
less than or equal to the value of the peer's "max-message-size"
attribute [I-D.ietf-mmusic-sctp-sdp] associated with the SCTP
association.
5.5. Data Sending, Receiving and Reporting
Data sending, receiving and reporting procedures SHALL conform to
[RFC4975].
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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:
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 Back-to-Back User Agent
(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 the MSRP CEMA mechanism [RFC6714] towards
the non-data channel endpoint.
o If the non-data channel endpoint does not support MSRP 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.
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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.
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
by [I-D.ietf-rtcweb-data-channel]. However, [RFC4975] allows
transport of MSRP traffic over non-secured TCP connections, and does
not provide a mechanism to guarantee usage of TLS end-to-end. As
described in [RFC4975], even if TLS is used between some hops TCP
might still be used between other hops. Operators need to ensure
that proper policies are established in order to ensure that the MSRP
traffic is protected between endpoints.
[RFC5547] specifies security considerations related to the usage of
MSRP for file transfer.
[RFC7092] specifies security considerations related to B2BUAs.
Note that discussion in Section 14.5 of [RFC4975] on MSRP message
attribution to remote identities applies to data channel transport.
If the Session Initiation Protocol (SIP) [RFC3261] is used to
implement the offer/answer transactions for establishing the MSRP
data channel, the SIP security considerations specified in [RFC3261]
apply.
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.
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A reference to RFCXXXX is added to the URI scheme "msrps" in the
Uniform Resource Identifier (URI) Schemes Registry.
9.2. Subprotocol Identifier MSRP
A reference to RFCXXXX is added to the subprotocol identifier "msrp"
in the "WebSocket Subprotocol Name Registry"
9.3. SDP Attributes
This document modifies the usage of a set of SDP attributes, if any
of those attributes is included in an SDP 'dsca' attribute associated
with an MSRP data channel. The modified usage of the SDP 'setup'
attribute is described in Section 4.5. The usage of the other SDP
attributes is described in Section 4.4.
o "path"
o "msrp-cema"
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"
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The usage level "dcsa(msrp)" is added to the registration of the SDP
'setup' attribute in the Session Description Protocol (SDP)
Parameters "att-field" sub-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
"att-field" sub-registry as follows:
+-----------------------+-------------------------------------------+
| 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 "att-field" sub-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 "att-field" sub-registry as follows:
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+-----------------------+-------------------------------------------+
| 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 "att-field" sub-registry as follows:
+-----------------------+-------------------------------------------+
| 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 "att-field" sub-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 "att-field" sub-registry as follows:
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+-----------------------+-------------------------------------------+
| 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 "att-field" sub-registry as follows:
+-----------------------+-------------------------------------------+
| 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 "att-field" sub-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 "att-field" sub-registry as follows:
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+-----------------------+-------------------------------------------+
| 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 "att-field" sub-registry as follows:
+-----------------------+-------------------------------------------+
| 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 "att-field" sub-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 "att-field" sub-registry as follows:
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+-----------------------+-------------------------------------------+
| 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 "att-field" sub-registry as follows:
+-----------------------+-------------------------------------------+
| Contact name: | IESG |
| Contact email: | iesg@ietf.org |
| Attribute name: | file-date |
| Usage level: | dcsa(msrp) |
| Purpose: | Indicate one or more dates 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 "att-field" sub-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 "att-field" sub-registry as follows:
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+-----------------------+-------------------------------------------+
| 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.
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. References
11.1. 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-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.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<https://www.rfc-editor.org/info/rfc3264>.
[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>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
[RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
"The Message Session Relay Protocol (MSRP)", RFC 4975,
DOI 10.17487/RFC4975, September 2007,
<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>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC7092] Kaplan, H. and V. Pascual, "A Taxonomy of Session
Initiation Protocol (SIP) Back-to-Back User Agents",
RFC 7092, DOI 10.17487/RFC7092, December 2013,
<https://www.rfc-editor.org/info/rfc7092>.
Authors' Addresses
Jose M. Recio (editor)
Unaffiliated
Email: jose@ch3m4.com
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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