CLUE Working Group C. Holmberg
Internet-Draft Ericsson
Intended status: Standards Track March 13, 2014
Expires: September 14, 2014
CLUE Protocol Data Channel
draft-holmberg-clue-datachannel-04
Abstract
This document defines how to use the WebRTC Data Channel mechanism,
together with the Data Channel Establishment Protocol (DCEP) in order
to establish a data channel, referred to as CLUE Data Channel, for
transporting CLUE protocol messages between two CLUE entities.
The document defines the SCTP considerations specific to a CLUE Data
Channel, the SDP offer/answer procedures for negotiating the
establishment of, and the DCEP procedures for opening, a CLUE Data
Channel.
Details and procedures associated with the CLUE protocol are outside
the scope of this document.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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 September 14, 2014.
Copyright Notice
Copyright (c) 2014 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
Holmberg Expires September 14, 2014 [Page 1]
Internet-Draft CLUE Protocol Data Channel March 2014
(http://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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. CLUE Data Channel . . . . . . . . . . . . . . . . . . . . . . 4
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Data Channel Establishment Protocol (DCEP) Usage . . . . 4
3.3. SCTP Considerations . . . . . . . . . . . . . . . . . . . 4
3.3.1. SCTP Payload Protocol Identifier (PPID) . . . . . . . 4
3.3.2. Reliability . . . . . . . . . . . . . . . . . . . . . 5
3.3.3. Order . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.4. Stream Reset . . . . . . . . . . . . . . . . . . . . 5
3.3.5. Interleaving . . . . . . . . . . . . . . . . . . . . 5
3.3.6. SCTP Multihoming . . . . . . . . . . . . . . . . . . 5
4. CLUE Data Channel Procedures . . . . . . . . . . . . . . . . 6
4.1. Open CLUE Data Channel . . . . . . . . . . . . . . . . . 6
4.2. Close CLUE Data Channel . . . . . . . . . . . . . . . . . 6
4.3. SCTP Association Failure . . . . . . . . . . . . . . . . 6
5. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 7
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. SDP Media Description Fields . . . . . . . . . . . . . . 7
5.3. SDP sctpmap Attribute . . . . . . . . . . . . . . . . . . 7
5.4. SDP Offerer Procedures . . . . . . . . . . . . . . . . . 8
5.5. SDP Answerer Procedures . . . . . . . . . . . . . . . . . 8
5.6. Example . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document defines how to use the WebRTC Data Channel mechanism
[I-D.ietf-rtcweb-data-channel], together with the Data Channel
Establishment Protocol (DCEP) [I-D.ietf-rtcweb-data-protocol] in
order to establish a data channel, referred to as CLUE Data Channel,
Holmberg Expires September 14, 2014 [Page 2]
Internet-Draft CLUE Protocol Data Channel March 2014
for transporting CLUE protocol [I-D.presta-clue-protocol] messages
between CLUE entities.
The document defines the SCTP considerations specific to a CLUE Data
Channel, the SDP offer/answer [RFC3264] procedures for negotiating
the establishment of, and the DCEP procedures for opening, a CLUE
Data Channel.
Details and procedures associated with the CLUE protocol are outside
the scope of this document.
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 BCP 14, RFC 2119
[RFC2119].
WebRTC Data Channel refers to a SCTPoDTLS association
[I-D.ietf-tsvwg-sctp-dtls-encaps] that is used to transport non-media
data between two entities, according to the procedures in
[I-D.ietf-rtcweb-data-channel].
CLUE Data Channel refers to a WebRTC Data Channel
[I-D.ietf-rtcweb-data-channel], with a specific set of SCTP
characteristics, and usage of the Data Channel Establishment Protocol
(DCEP) [I-D.ietf-rtcweb-data-protocol] in order to open a WebRTC Data
Channel for the purpose of transporting CLUE protocol
[I-D.presta-clue-protocol] messages between two CLUE entities.
CLUE entity refers to a SIP User Agent (UA) [RFC3261] that supports
the CLUE Data Channel and the CLUE protocol.
CLUE session refers to a SIP session [RFC3261] between to SIP UAs,
where a CLUE Data Channel, associated with the SIP session, has been
established between the SIP UAs.
[RFC4960] defines an SCTP stream as a unidirectional logical channel
established from one to another associated SCTP endpoint, within
which all user messages are delivered in sequence except for those
submitted to the unordered delivery service.
[RFC4960] defines an SCTP identifier as a unsigned integer, which
identifies a SCTP stream.
Holmberg Expires September 14, 2014 [Page 3]
Internet-Draft CLUE Protocol Data Channel March 2014
3. CLUE Data Channel
3.1. General
This section describes the realization of a CLUE Data Channel. This
includes a set of SCTP characteristics specific to a CLUE Data
Channel, and usage of the Data Channel Establishment Protocol (DCEP)
[I-D.ietf-rtcweb-data-protocol] in order to open a WebRTC Data
Channel for the purpose of transporting CLUE protocol
[I-D.presta-clue-protocol] messages between two CLUE entities.
As described in [I-D.ietf-rtcweb-data-channel], the SCTP streams
realizing a WebRTC Data Channel must be associated with the same SCTP
association. In addition, both SCTP streams realizing the WebRTC
Data Channel must use the same SCTP stream identifier value. These
rules also apply to a CLUE Data Channel.
Within a given CLUE session, a CLUE entity MUST use a single CLUE
Data Channel for transport of all CLUE messages towards its peer.
3.2. Data Channel Establishment Protocol (DCEP) Usage
A CLUE entity MUST use the Data Channel Establishment Protocol (DCEP)
[I-D.ietf-rtcweb-data-channel], in order to open a CLUE Data Channel.
The details of the DCEP usage with a CLUE Data Channel are described
in section X.X.X.
3.3. SCTP Considerations
3.3.1. SCTP Payload Protocol Identifier (PPID)
As described in [I-D.ietf-rtcweb-data-protocol], the PPID value 50 is
used when sending a DCEP message on a WebRTC Data Channel.
A CLUE entity MUST use the PPID value 51 when sending a CLUE message
on a CLUE Data Channel.
NOTE: As described in [I-D.ietf-rtcweb-data-channel], the PPID value
51 indicates that the SCTP message contains data encoded in a UTF-8
format. The PPID value 51 does not indicate what application
protocol is transported in a WebRTC Data Channel, only the format in
which the data is encoded.
Holmberg Expires September 14, 2014 [Page 4]
Internet-Draft CLUE Protocol Data Channel March 2014
+----------+------------+
| Protocol | PPID Value |
+----------+------------+
| DCEP | 50 |
| CLUE | 51 |
+----------+------------+
Table 1: CLUE Data Channel PPID Values
3.3.2. Reliability
The usage of SCTP for the CLUE Data Channel ensures reliable
transport of CLUE protocol [I-D.presta-clue-protocol] messages.
NOTE: [I-D.ietf-rtcweb-data-channel] requires the support of the
partial reliability extension defined in [RFC3758]. This is not
needed for a CLUE Data Channel, as messages are required to always be
sent reliably. [I-D.ietf-rtcweb-data-channel] also mandates support
of the limited retransmission policy defined in
[I-D.tuexen-tsvwg-sctp-prpolicies].
3.3.3. Order
A CLUE entity MUST use the ordered delivery SCTP service, as
described in section 6.6 of [RFC2960].
3.3.4. Stream Reset
A CLUE entity MUST support the stream reset extension defined in
[RFC6525].
The dynamic address reconfiguration extension defined in [RFC5061]
MUST be used to signal the support of the stream reset extension
defined in [RFC6525]. Other features of [RFC5061] MUST NOT be used.
3.3.5. Interleaving
A CLUE entity MUST support the message interleaving mechanism defined
in [I-D.stewart-tsvwg-sctp-ndata].
3.3.6. SCTP Multihoming
SCTP multihoming cannot be used for a CLUE Data Channel.
NOTE: SCTPoDTLS does not support SCTP multihoming.
Holmberg Expires September 14, 2014 [Page 5]
Internet-Draft CLUE Protocol Data Channel March 2014
4. CLUE Data Channel Procedures
4.1. Open CLUE Data Channel
Once the SCTP association, to be used to realized the CLUE Data
Channel, has been established, the offerer [RFC3264] is responsible
for opening the CLUE Data Channel. The offerer MUST send a DCEP
DATA_CHANNEL_OPEN message [I-D.ietf-rtcweb-data-protocol]. The value
of the 'protocol' field MUST be "CLUE".
NOTE: A new 'protocol' value for CLUE needs to be registered with
IANA in the 'Protocol Registry' defined by
[I-D.ietf-rtcweb-data-protocol].
Once the offerer has received the associated DCEP DATA_CHANNEL_ACK
message [I-D.ietf-rtcweb-data-protocol], the CLUE Data channel has
been opened.
If the Offerer receives a DCEP DATA_CHANNEL_OPEN message, for the
purpose of opening a CLUE Data Channel, the offerer MUST reset the
SCTP stream, in order to prevent two CLUE Data Channels from being
established within the same CLUE session. The offerer MUST NOT send
a DCEP DATA_CHANNEL_ACK message.
4.2. Close CLUE Data Channel
DCEP [I-D.ietf-rtcweb-data-protocol] does not define a message for
closing a WebRTC Data Channel. Instead, in order to close a CLUE
Data Channel, a SCTP reset message is sent, in order to close the
SCTP stream associated with the CLUE Data Channel. The SCTP
association, and WebRTC Data Channels associated with other SCTP
streams, are not affected by the SCTP reset message.
Section X.X.X describes how to terminate the SCTP association used
for the CLUE data channel.
4.3. SCTP Association Failure
In case of SCTP association failure, the offerer is responsible for
trying to re-establish the SCTP association (including sending a new
SDP offer, if needed). Once the SCTP association has been
successfully re-established, the offerer is responsible for sending a
DCEP DATA_CHANNEL_OPEN message.
Holmberg Expires September 14, 2014 [Page 6]
Internet-Draft CLUE Protocol Data Channel March 2014
5. SDP Offer/Answer Procedures
5.1. General
This section describes how an SDP media description ("m=") line
describing a SCTPoDTLS association, to be used to realize a CLUE Data
Channel, is created, and how it is used in SDP offers and answers
[RFC3264].
NOTE: The procedures associated with creating an "m=" line describing
media (e.g. audio and video) for a CLUE session are outside the scope
of this document.
OPEN ISSUE (Q1): It is FFS whether the SDP-based WebRTC Data Channel
Negotiation mechanism [I-D.ejzak-dispatch-webrtc-data-channel-sdpneg]
will be used with the CLUE Data Channel. It depends on whether the
draft will progress in MMUSIC, and whether it will be finalized
before the publication of the CLUE mechanism.
OPEN ISSUE (Q2): As the SDP offer/answer procedures are generic to
SCTPoDTLS association, it is FFS whether we need to specify them, or
whether we can simply refer to Salvatore's draft.
5.2. SDP Media Description Fields
The field values of the "m=" line for the SCTPoDTLS association are
set as following:
+---------------+----------------+-----------------+----------------+
| media | port | proto | fmt |
+---------------+----------------+-----------------+----------------+
| "applicationS | DTLS port | "UDP/TLS/UDPTL" | SCTP port |
| | value | | value |
+---------------+----------------+-----------------+----------------+
Table 2: SDP "proto" field values
5.3. SDP sctpmap Attribute
The field values of the SDP sctpmap attribute, associated with the
"m=" line describing the SCTPoDTLS association, are set as following:
Holmberg Expires September 14, 2014 [Page 7]
Internet-Draft CLUE Protocol Data Channel March 2014
+----------------------------+----------------------+
| sctpmap-number | app |
+----------------------------+----------------------+
| fmt value of the "m=" line | "webrtc-datachannel" |
+----------------------------+----------------------+
Table 3: SDP "proto" field values
5.4. SDP Offerer Procedures
The procedures for the offerer follow the normal procedures defined
in [RFC3264].
When the offerer creates an offer, which contains an "m=" line
describing a SCTPoDTLS association, it assigns the field values to
the "m=" line according to the procedures in Section 5.2. In
addition, the offerer MUST insert an SDP sctpmap attribute associated
with the "m=" line.
In an offer, the offerer MUST NOT insert more than one "m=" line
describing an SCTPoDTLS association to be used to realize a CLUE Data
Channel.
If an offerer, in a subsequent offer, wants to disable the CLUE Data
Channel, it assigns a zero port value to the "m=" line describing the
SCTPoDTLS association used to realize the CLUE Data Channel.
5.5. SDP Answerer Procedures
The procedures for the answerer follow the normal procedures defined
in [RFC3264].
If the answerer receives an offer, which contains an "m=" line
describing a SCTPoDTLS association, and the answerer accepts the "m="
line, it inserts an "m=" line in the corresponding answer, and
assigns the "m=" line field values according to the procedures in
Section 4.2.
If the answerer receives an offer, which contains an "m=" line
describing a SCTPoDTLS association, and the answerer does not accept
the "m=" line, it inserts an "m=" line in the corresponding answer,
and assigns a zero port value to the "m=" line, according to the
procedures in [RFC3264].
If the answerer receives an offer, in which a zero port value has
been assigned to an "m=" line describing the SCTPoDTLS association,
it inserts an "m=" line in the corresponding answer, and assigns a
Holmberg Expires September 14, 2014 [Page 8]
Internet-Draft CLUE Protocol Data Channel March 2014
zero port value to the "m=" line, according to the procedures in
[RFC3264]
OPEN ISSUE (Q3): We need to determine whether an "m=" line describing
an SCTPoDTLS association can be used together with bundle-only, in
which case there will be cases where an offer with a zero port value
will create a corresponding answer with a non-zero port value.
5.6. Example
m=application 54111 SCTP/DTLS 54111
a=sctpmap:54111 webrtc-datachannel
Figure 1: SDP Media Description for a CLUE Data Channel
6. Security Considerations
This specification does not introduce new security considerations, in
addition to those defined in [ref-to-data-channel] and [ref-to-data-
protocol]. Security considerations associated with the CLUE protocol
are defined in [ref-to-clue-protocol].
7. IANA Considerations
[RFC EDITOR NOTE: Please replace RFC-XXXX with the RFC number of this
document.]
8. Acknowledgments
Thanks to Paul Kyzivat and Christian Groves for comments on the
document.
9. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-holmberg-clue-datachannel-03
o Procedures updated, based on WG agreement (IETF#89) to use DCEP
for the CLUE data channel.
o Procedures updated, based on WG agreement (IETF#89) that SDP
Offerer is responsible for sending DCEP DATA_CHANNEL_OPEN.
o Editorial changes, and alignments caused by changes in referenced
specifications.
Changes from draft-holmberg-clue-datachannel-02
o PPID value for CLUE messages added
Holmberg Expires September 14, 2014 [Page 9]
Internet-Draft CLUE Protocol Data Channel March 2014
o References updated
Changes from draft-holmberg-clue-datachannel-01
o More text added
Changes from draft-holmberg-clue-datachannel-00
o Editorial corrections based on comments from Paul K
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
Zhang, L., and V. Paxson, "Stream Control Transmission
Protocol", RFC 2960, October 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June
2002.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061, September
2007.
[RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control
Transmission Protocol (SCTP) Stream Reconfiguration", RFC
6525, February 2012.
[I-D.presta-clue-protocol]
Presta, R. and S. Romano, "CLUE protocol", draft-presta-
clue-protocol-03.txt (work in progress), November 2013.
Holmberg Expires September 14, 2014 [Page 10]
Internet-Draft CLUE Protocol Data Channel March 2014
[I-D.ietf-tsvwg-sctp-dtls-encaps]
Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS
Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp-
dtls-encaps-02.txt (work in progress), October 2013.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-07.txt (work in
progress), February 2014.
[I-D.ietf-rtcweb-data-protocol]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel
Establishment Protocol", draft-ietf-rtcweb-data-
protocol-03.txt (work in progress), February 2014.
[I-D.stewart-tsvwg-sctp-ndata]
Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "A
New Data Chunk for Stream Control Transmission Protocol",
draft-stewart-tsvwg-sctp-ndata-03.txt (work in progress),
October 2013.
[I-D.tuexen-tsvwg-sctp-prpolicies]
Tuexen, M., Seggelmann, R., Stewart, R., and S. Loreto,
"Additional Policies for the Partial Delivery Extension of
the Stream Control Transmission Protocol", draft-tuexen-
tsvwg-sctp-prpolicies-03.txt (work in progress), October
2013.
10.2. Informative References
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004.
[I-D.ejzak-dispatch-webrtc-data-channel-sdpneg]
Ejzak, R. and J. Marcon, "SDP-based WebRTC data channel
negotiation", draft-ejzak-dispatch-webrtc-data-channel-
sdpneg-00.txt (work in progress), October 2013.
Author's Address
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Holmberg Expires September 14, 2014 [Page 11]
