CLUE Protocol Data Channel
draft-ietf-clue-datachannel-00

CLUE Working Group                                           C. Holmberg
Internet-Draft                                                  Ericsson
Intended status: Standards Track                          March 20, 2014
Expires: September 21, 2014

                       CLUE Protocol Data Channel
                     draft-ietf-clue-datachannel-00

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 21, 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

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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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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  . . . . . . . . . . . . . . . . . .   6
   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  . . . . . . . . . . . . . . . .   7
   5.  SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . .   7
     5.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  SDP Media Description Fields  . . . . . . . . . . . . . .   7
     5.3.  SDP sctpmap Attribute . . . . . . . . . . . . . . . . . .   8
     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 . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

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,

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   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.

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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 support the Data Channel Establishment Protocol
   (DCEP) [I-D.ietf-rtcweb-data-channel], which can be used in order to
   open a WebRTC Data Channel.

   In the absence of some other mechanism, a CLUE entity MUST use DCEP
   in order to open a CLUE Data Channel.

   NOTE: This document does not define any other mechanism for opening a
   CLUE Data Channel, but such might be defined in future
   specifications.

   The details of the DCEP usage with a CLUE Data Channel are described
   in Section 4.1.

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

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   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.

                         +----------+------------+
                         | 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.

   A CLUE entity MUST NOT use the partial reliability and limited
   retransmission extensions defined in [RFC3758].

   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 [RFC4960].

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].

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3.3.6.  SCTP Multihoming

   SCTP multihoming cannot be used for a CLUE Data Channel.

   NOTE: SCTPoDTLS does not support SCTP multihoming.

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.  If DCEP is used, 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".  The value of the 'channel type' MUST be
   'DATA_CHANNEL_RELIABLE'.

   OPEN ISSUE: We need to determine whether we shall include a version
   number in the 'protocol' field value for 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.  As described in
   [I-D.ietf-rtcweb-data-protocol], 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 5.4 describes how to terminate the SCTP association used for
   the CLUE data channel.

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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.

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 draft-ietf-mmusic-sctp-sdp.

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       |
    +---------------+-----------------+-------------+-----------------+
    | "application" | DTLS port value | "DTLS/SCTP" | SCTP port value |
    +---------------+-----------------+-------------+-----------------+

                     Table 2: SDP "proto" field values

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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:

           +----------------------------+----------------------+
           |       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.

   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

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   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-04

   o  Draft submitted as draft-ietf-clue-data-channel-00.
   o  Editorial nits fixed.
   o  Changes based on comments from Paul Kyzivat (http://www.ietf.org/
      mail-archive/web/clue/current/msg03559.html).
   o  - Proto value fixed.
   o  - Explicit text that the partial reliability and limited
      retransmission policies MUST NOT be used.
   o  - Added open issue on whether the DCEP 'protocol' field value for
      CLUE should contain a version number.

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   o  - Removed paragraph saying that an offerer must not insert more
      than one m- line describing an SCTPoDTLS association to be used to
      realize a CLUE Data Channel, as the draft already states that only
      one CLUE Data Channel per CLUE session shall be opened.
   o  - Added reference to draft-ietf-rtcweb-data-protocol regarding
      details on reseting SCTP streams.
   o  - Added text saying that the value of the DCEP 'channel type' MUST
      be DATA_CHANNEL_RELIABLE.
   o  - Clarified that DCEP must be supported, and used in the absence
      of another mechanism for opening a CLUE Data Channel.

   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 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
   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.

   [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.

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   [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.

   [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-03.txt (work in progress), February 2014.

   [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.

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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

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