[clue] CLUE Data Channel: SDP Offer/Answer Proceudres

[Christer Holmberg <[e-mail]>]

Hi,

The draft submission deadline has passed, but I still wrote some more text, shown below, for the SDP Offer/Answer Procedures section.

Regards,

Christer

PS. Note that I will be on vacation next week, so I will once again do my best trying to stay away from e-mails :)

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4.  SDP Offer/Answer Procedures

4.1.  General

   This section describes how the SDP media description ("m=") line for
   a CLUE data channel is created, and how it is used in SDP offers and
   answers.

   NOTE: The proceudres associated with "m=" lines for other media types
   (e.g. audio and video) used in a CLUE session are outside the scope
   of this document.

   OPEN ISSUE #3: 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.

   NOTE: If [I-D.ejzak-dispatch-webrtc-data-channel-sdpneg] will be used
   with the CLUE data channel, a new associated 'sub-protocol' value
   needs to be registered with IANA.

4.2.  SDP Media Description Fields

   The field values of the "m=" line for the CLUE data channel are set
   as following:

   +----------------+----------------+------------------------+----------------+
   |     media      |      port         |      proto               |      fmt         |
   +----------------+----------------+------------------------+----------------+
   | "applicationS |   DTLS port   | "UDP/TLS/UDPTL" |   SCTP port   |
   |                    |     value       |                             |     value       |
   +----------------+----------------+------------------------+---------------+

                     Table 1: SDP "proto" field values

4.3.  SDP sctpmap Attribute

   The field values of the SDP sctpmap attribute associated with the
   CLUE data channel "m=" are set as following:

   +---------------------+---------------------------+-----------------------+---------+
   | sctpmap-number |         app                  | max-message-size | stream |
   +---------------------+---------------------------+-----------------------+---------+
   |  fmt value of       | "webrtc-datachannel" |  Implemenation     |  "1"     |
   | the "m=" line      |                                |     specific             |           |
   +---------------------+---------------------------+-----------------------+---------+

                     Table 2: SDP "proto" field values

4.4.  SDP Offerer Procedures

   The procedures for the offerer follow the normal proceures defined in
   [ref-to-3264].

   When the offerer creates an offer, which contains an "m=" line for a
   CLUE data channel, it assigns the field values to the "m=" line
   according to the procedures in Section 4.2.  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 for
   a CLUE data channel.

   NOTE: CLUE does not support the usage of multiple CLUE data channels.

   The offerer MUST NOT insert more than one SDP sctpmap attributes in
   an "m=" line for 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 associated
   with the CLUE data channel.  The answerer MUST NOT insert an SDP
   sctpmap attribute associated with the "m=" line.

4.5.  SDP Answerer Procedures

   The procedures for the answerer follow the normal proceures defined
   in [ref-to-3264].

   If the answerer receives an offer, which contains an "m=" line for a
   CLUE data channel, and the answerer accepts the "m=" line, it creates
   and inserts an "m=" line in the associated answer.  The answerer
   assigns the field values to the "m=" line according to the procedures
   in Section 4.2.

   If, in the offer, a zero port value has been assigned to the "m="
   line for the CLUE channel, or it the answerer does not accept the
   "m=" line, but accepts other "m=" lines in the offer (i.e. the
   answerer will not reject the whole offer), it still inserts an "m="
   line for a CLUE data channel in the associated answer.  The answerer
   then assigns a zero port value to the "m=" line.  The answerer MUST
   NOT insert an SDP sctpmap attribute associated with the "m=" line.

4.6.  Example

        m=application 54111 SCTP/DTLS 54111
        a=sctpmap:54111 webrtc-datachannel max-message-size=100000 streams=1

          Figure 1: SDP Media Description for a CLUE data channel