Content for  TS 24.186  Word version:  18.0.0

If the UE wants to establish a bootstrap data channel, the UE shall take into account the data channel configuration as specified in clause 9.3.2.1.1, and if the UE determines that the configuration allows the establishment of IMS data channels after the establishment of the MMTel session, the UE shall:

1. generate a re-INVITE request in accordance with TS 24.229 and TS 24.173;
2. include the media feature tag defined in RFC 5688 for supported streaming media type with +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114 in the Contact header field; and
3. include an updated SDP offer that contains data channel media description(s) for the bootstrap data channel(s) according to TS 26.114.

Upon receiving a re-INVITE request to establish a bootstrap data channel, the procedure defined in clause 9.3.3.1.3.1 applies.

If a UE wants to establish an application data channel within an existing MMTel session and if the UE has an established bootstrap data channel associated with the MMTel session available, the UE:

1. shall generate a re-INVITE request in accordance with TS 24.229 and TS 24.173;
2. shall include the media feature tag defined in RFC 5688 for supported streaming media type with +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114 in the Contact header field; and
3. shall include an updated SDP offer that contains a data channel media description for the bootstrap data channel, as well as the requested application data channel and the associated DC application binding information (provided within the "a=3gpp-req-app" SDP attribute), according to TS 26.114.

If the UE has an established bootstrap data channel associated with the MMTel session available and if the UE receives the re-INVITE request with an SDP offer which includes data channel media descriptions for the bootstrap data channel, as well as the requested application data channel, the procedure defined in clause 9.3.3.1.3.2 applies.

If the IMS AS received from the originating UE a re-INVITE request with the SDP offer containing data channel media description for the bootstrap data channel establishment, the procedure defined in clause 9.3.2.2.1 applies.

After the DCSF is selected, upon receipt of the re-INVITE request with an SDP offer which contains a new application data channel media description (the media line with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000) along with the video, audio, and bootstrap data channel media descriptions, the IMS AS shall notify to DCSF about a media change request event and request the MF to allocate media resources for the application data channels based on the instruction from the DCSF if the media is anchored on the MF, and shall not send a re-INVITE request to the S-CSCF until receiving an acknowledgement to the corresponding notification from the DCSF. Based on the response on the data channel media resource update from the MF and media instruction from the DCSF as specified in 3GPP TS 29.175 [18], the IMS AS shall:

1. delete the data channel media description (media line with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000 and "a=3gpp-req-app" attribute with "endpoint" parameter set to value "server") if the media instruction from the DCSF is to terminate that media;
2. delete the data channel media description if the media instruction from the DCSF is to reject the media;
3. modify the data channel media description if the media instruction from the DCSF is to terminate and originate the media:
   • replace the DC endpoint information in the SDP offer with the media resource information on the termination towards to the terminating network which is allocated by the MF;
4. generate and add a data channel media description (media line with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000 and "a=3gpp-req-app" attribute with "endpoint" parameter set to value "server") if the media instruction from the DCSF is to originate a new media;

Upon receipt of the re-INVITE request with an SDP offer which contains an existing application data channel media description in which the a new "a=dcmap" line containing the "stream-id" parameter set to values starting at 1000 is added, the IMS AS shall notify the DCSF about media change request event, and request MF to update the media resource when receiving the media instruction from DCSF is to update the media. Upon the reception of an acknowledgement from the DCSF to the media change request event notification, the IMS AS shall send the re-INVITE request with the modified SDP offer with the modified application data channel media description as well as the media description of established video, audio and bootstrap data channels. Upon receipt of the 200 (OK) response on the re-INVITE request with the SDP answer which contains media description of the requested application data channel from the terminating network, the IMS AS shall notify to DCSF about the media change success or the media change failure event and request the MF to update or release the media resources. The IMS AS shall modify the application data channel media description in the SDP answer and send 200 (OK) response with the modified SDP answer for the requested application data channel to S-CSCF after the receipt of an acknowledgement from the DCSF to the corresponding notification. Upon receiving the re-INVITE request from the terminating network to setup data channels and the corresponding 200 (OK) response from the originating UE, the procedure in clause 9.3.3.2.2 applies.

Upon receipt of the re-INVITE request with an SDP offer which contains an existing application data channel media description in which an existing "a=dcmap" is removed, the IMS AS shall notify the DCSF about media change request event, and request MF to update the media resource when receiving the media instruction from DCSF is to update the media. Upon receipt of the re-INVITE request with an SDP offer which contains an existing application data channel media description in which the UDP port number is set to 0, the IMS AS shall notify the DCSF about media change request event, and request the MF to release the corresponding media resource when receiving the media instruction from the DCSF is to delete the media. Upon receipt of the 200 (OK) response on the re-INVITE message with the SDP answer, the procedure in clause 9.3.2.2.2.2 applies. Upon receiving the re-INVITE request from the terminating network to close data channels and the corresponding 200 (OK) response from the originating UE, the procedure in clause 9.3.3.2.2.3 applies.