Content for TS 24.186 Word version: 19.0.0

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9.3 MMTel session procedures 9.3.1 General 9.3.2 Originating side 9.3.2.1 Procedures at the UE 9.3.2.1.1 General 9.3.2.1.2 IMS bootstrap data channel setup in conjunction with MMTel session setup 9.3.2.1.3 IMS data channel setup in conjunction with MMTel session modification 9.3.2.1.3.1 IMS bootstrap data channel establishment 9.3.2.1.3.2 IMS application data channel establishment 9.3.2.1.4 Closing IMS application data channel in conjunction with MMTel session modification 9.3.2.1.5 Closing IMS data channel in conjunction with MMTel session release 9.3.2.2 Procedure at the IMS AS 9.3.2.2.1 IMS bootstrap data channel establishment in conjunction with MMTel session setup 9.3.2.2.2 MMTel session modification 9.3.2.2.2.1 IMS bootstrap data channel establishment 9.3.2.2.2.2 IMS application data channel establishment 9.3.2.2.2.3 Closing application data channel 9.3.2.2.3 MMTel session release
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9.3 MMTel session procedures p. 13

9.3.1 General p. 13

The support of the IMS data channel is optional.

The session control procedures for IMS multimedia telephony communication service with IMS data channel shall be in accordance with TS 24.173 with the additions defined in the present document.

9.3.2 Originating side p. 13

9.3.2.1 Procedures at the UE p. 13

9.3.2.1.1 General p. 13

The UE shall only initiate an MMTel session with an IMS data channel if the UE has determined that the UE and the home network supports the IMS data channel capability.

The policy related to the UE supporting the IMS data channel can be provided by the home network to the UE using e.g. OMA-DM with the management objects specified in TS 24.275 or UICC configuration, as specified in clause 9.2.1.1. When the UE is configured by home network with configuration for IMS data channel, then the UE may setup the IMS data channel.

If the UE is configured with IMS_DC_configuration node specified in TS 24.275 and:

DC_allowed leaf indicates that IMS data channel is not allowed, the UE shall not include data channel capability indication and data channel related media description in SDP offer;
DC_allowed leaf indicates that IMS data channel is allowed, and:
1. if DC_Setup_Option leaf is configured and indicates the IMS data channel is allowed to be setup simultaneously while establishing an MMTel session, the UE:
  - shall include the bootstrap data channel related media description in SDP offer within the initial INVITE request as described in clause 9.3.2.1.2 to setup the bootstrap data channel;
  NOTE 1:
  If the bootstrap data channel was not established during the MMTel session establishment, the UE can try to setup the bootstrap data channel as described in clause 9.3.2.1.3.
2. if DC_Setup_Option leaf is configured and indicates the IMS data channel is not allowed to be setup simultaneously while establishing an MMTel session, the UE shall generate a re-INVITE request for the bootstrap data channel setup and include the bootstrap data channel related media description in SDP offer as described in clause 9.3.2.1.3 to setup the bootstrap data channel; and
3. if the UE receives an initial INVITE or a re-INVITE request including the bootstrap data channel related media description in SDP offer, the UE shall generate an SDP answer as described in clause 9.3.3.1.

If the UE is configured with EFIMSDCI file specified in TS 31.103 or TS 31.102 and:

if IMS DC Establishment Indication indicates that IMS data channel is not allowed, the UE shall not include data channel capability indication and data channel related media description in SDP offer;
if IMS DC Establishment Indication indicates that IMS data channel is allowed and allowed to be setup simultaneously while establishing an MMTel session, the UE shall include the bootstrap data channel related media description in SDP offer within the initial INVITE request as described in clause 9.3.2.1.2 to setup the bootstrap data channel;

NOTE 2:
If the bootstrap data channel was not established during the MMTel session establishment, the UE can try to setup the bootstrap data channel as described in clause 9.3.2.1.3.
if IMS DC Establishment Indication indicates that IMS data channel is allowed but not allowed to be setup simultaneously while establishing an MMTel session, the UE shall generate a re-INVITE request for the bootstrap data channel setup and include the bootstrap data channel related media description in SDP offer as described in clause 9.3.2.1.3 to setup IMS data channel; and
if IMS DC Establishment Indication indicates that IMS data channel is allowed, if the UE receives an initial INVITE or a re-INVITE request including the bootstrap data channel related media description in SDP offer, the UE shall generate an SDP answer as described in clause 9.3.3.1.

9.3.2.1.2 IMS bootstrap data channel setup in conjunction with MMTel session setup p. 14

If the UE initiates an MMTel session with IMS data channels, the UE:

shall generate an initial INVITE request in accordance with TS 24.229 and TS 24.173;
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;
may include an Accept-Contact header field containing the "sip.app-subtype" media feature tag defined in RFC 5688 with a value of "webrtc-datachannel" as specified in TS 26.114; and
if the configuration described in clause 9.3.2.1.1, allows the establishment of bootstrap data channels simultaneously with the setup of the MMTel session, shall include an SDP offer containing the media descriptions for the MMTel media according TS 24.173 and data channel media descriptions for both the local and remote bootstrap data channels in accordance with TS 26.114.

9.3.2.1.3 IMS data channel setup in conjunction with MMTel session modification p. 15

9.3.2.1.3.1 IMS bootstrap data channel establishment p. 15

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:

generate a re-INVITE request in accordance with TS 24.229 and TS 24.173;
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
include an updated SDP offer that contains data channel media descriptions for both the local and remote bootstrap data channels 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.

9.3.2.1.3.2 IMS application data channel establishment p. 16

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:

shall generate a re-INVITE request in accordance with TS 24.229 and TS 24.173;
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
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.

9.3.2.1.4 Closing IMS application data channel in conjunction with MMTel session modification p. 15

If the UE wants to close an established application data channel during the session modification by sending re-INVITE request with the subsequent SDP offer, the UE shall remove the "a=dcmap" attribute line associated with the closed application data channel and, if the associated "a=3gpp-req-app" attribute references only the closed application data channel, the "a=3gpp-req-app" attribute line from the data channel media description as defined in Section 6.6.1 of RFC 8864 or set the UDP port number of the data channel media description to zero if no other "a=dcmap" attribute line associated with an application data channel or bootstrap data channel existed in this data channel media description.

If the UE receives a re-INVITE request with an SDP offer in which the UDP port number of the data channel media description was set to zero or the "a=dcmap" line associated with an application data channel was removed from the data channel media description, and the UE accepts the application data channel termination, it shall return a 200 (OK) response to the re-INVITE request with the generated SDP answer based on the RFC 8864.

The UE shall not close the bootstrap data channel during MMTel session modification procedure.

9.3.2.1.5 Closing IMS data channel in conjunction with MMTel session release p. 15

When the UE releases an MMTel session that has associated bootstrap and application data channels, the UE shall apply procedures defined in clause 5.1.5 of TS 24.229 and shall close bootstrap and application data channels.

9.3.2.2 Procedure at the IMS AS p. 16

9.3.2.2.1 IMS bootstrap data channel establishment in conjunction with MMTel session setup p. 16

Based on served user service specific data which is enhanced with IMS data channel specific service details, if the IMS AS received an initial INVITE request with an SDP offer containing media description for IMS data channels, the IMS AS shall determine whether the served user is authorized to use IMS data channel.

If the served user is not authorized to use IMS data channel, then based on the operator policy the IMS AS shall determine whether to remove from the SDP offer media lines related to the IMS data channels:

If the operator policy indicates removal of media lines related to the IMS data channels, the IMS AS shall remove media lines describing the bootstrap data channel(s) i.e. "dcmap" attribute lines containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0, 10, 100 and 110, and associated with the "m=" line containing the media set to "application", the UDP port number, the proto value set to "UDP/DTLS/SCTP" and the fmt value set to "webrtc-datachannel". If there are no other "dcmap" attribute lines that contain a subprotocol parameter set to value other than "http", the IMS AS shall remove any other SDP media attribute lines associated with that m line e.g., "sctp-port", "max-message-size", "tls-id", "a=setup", "a=3gpp-qos-hint" SDP attribute lines from the received SDP offer, and send the initial INVITE request with the modified SDP offer to the S-CSCF.
If the operator policy does not indicate removal of media lines related to the IMS data channels, the IMS AS may forward media description describing the bootstrap data channel with "dcmap" attribute lines containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110, and send the initial INVITE request to the S-CSCF.

Otherwise, if the served user is authorized to use IMS data channel and the DCSF is not selected, the IMS AS shall select a DCSF and notify the DCSF about the session establishment request event, and shall not send the initial INVITE request to the S-CSCF until receiving an acknowledgement to the corresponding notification from the DCSF.

Based on the received Media instruction set from the DCSF, the IMS AS shall select a MF and request the MF to allocate required data channel media resources. Based on the response of the reserved media resource from the MF, the IMS AS shall:

delete the bootstrap data channel media description terminated locally, i.e. local bootstrap data channel for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10);
replace the IP address represented in the attribute lines "c=" line, the UDP port number in the "m=application" line, as well as the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" within the remote bootstrap data channel media description for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110), i.e. the remote bootstrap data channel between the originating UE and terminating network, received in the SDP offer with the media resource information for the termination towards the remote network allocated on the MF if the media is anchored on the originating MF, and add "a=3gpp-bdc-used-by:" attribute line containing "bdc-used-by" parameter set to value "sender" if not present; and
generate and add the remote bootstrap data channel media description for the terminating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by:" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. remote bootstrap data channel between the originating network and the terminating UE.

Upon the reception of the successful acknowledgement to the corresponding notification from the DCSF, the IMS AS shall send the initial INVITE request with audio, video and modified data channel SDP offer to the S-CSCF towards the terminating network.

Upon receipt the 18x or 2xx response on the initial INVITE request including the SDP answer which includes the data channel media description, the IMS AS shall notify the DCSF about corresponding session event (session establishment progress (i.e. receiving the 183 (Session Progress) response ), session establishment alerting (i.e. receiving the 180 (Ringing) response) or session establishment success (i.e. receiving 200 (OK) response) event) and shall request the MF to update the media resource. Based on the media resource update response from the MF, the IMS AS shall:

delete the remote bootstrap data channel media description for the terminating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. the remote bootstrap data channel between terminating UE and originating network from the SDP answer;
replace the IP address represented in the "c=" line, the UDP port number in the "m=application" line, as well as the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" within the remote bootstrap data channel media description for originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and110 and "a=3gpp-bdc-used-by" attribute with "bdc-used-by" parameter set to value "sender") in the SDP answer if the media is anchored on the MF, i.e. the remote data channel for the originating UE between originating UE and terminating network, with the media resource information for the termination towards the originating UE to the terminating network allocated by the MF; and
generate and add the local bootstrap data channel media description for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and10), i.e. the local bootstrap data channel between originating UE and originating network in the SDP answer.

Upon the reception of an acknowledgement from the DCSF to the corresponding notification, the IMS AS shall include the modified SDP answer for data channel in the 18x or 2xx response and send 18x or 2xx response to S-CSCF towards the originating UE.

Upon receipt of a CANCEL request to the initial INVITE request, the IMS AS shall notify the DCSF about the session establishment cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request to the S-CSCF towards the terminating network.

Upon receipt of a 4xx, 5xx or 6xx response on the initial INVITE request from the terminating network, the IMS AS shall notify the DCSF about session establishment failure, and request the MF to release the data channel media resources.

9.3.2.2.2 MMTel session modification p. 17

9.3.2.2.2.1 IMS bootstrap data channel establishment p. 17

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 IMS AS shall determine whether the served user is authorized to use IMS data channel or not as specified in clause 9.3.2.2.1.

if the served user is not authorized to use IMS data channel, the procedure defined in clause 9.3.2.2.1 applies; and
if the served user is authorized to use IMS data channel, the IMS AS shall select a DCSF and notify the DCSF about the media change request event and modify the data channel media description in the SDP offer and send the re-INVITE request as per clause 9.3.2.2.1. Upon receipt of the 183 (Session Progress) or 200 (OK) response to the re-INVITE request, the IMS AS shall send notify the DCSF about the media change success if the data channel media is accepted or media change failure if the data channel media is rejected and modify the data channel media description in the SDP answer and send the 183 (Session Progress) or 200(OK) response to S-CSCF as per clause 9.3.2.2.1. Upon receipt of a CANCEL request to the re-INVITE request, the IMS AS shall notify the DCSF about the media change cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request as per clause 9.3.2.2.1. Upon receipt of a 4xx, 5xx or 6xx response on the re-INVITE request, the IMS AS shall notify the DCSF about the media change failure and forward the response to the originating UE.

If the IMS AS received from the terminating network a re-INVITE request with the SDP offer containing data channel media description for the bootstrap data channel establishment, the procedure of the IMS AS in the terminating network on receipt of a re-INVITE request from the originating network defined in clause 9.3.3.2.2.1 applies.

9.3.2.2.2.2 IMS application data channel establishment p. 17

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 as specified in TS 29.176 and media instruction from the DCSF as specified in TS 29.175, 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. replace the IP address represented in the "c=" line, the UDP port number in the "m=application"in the data channel media description in the SDP offer with the media resource information for the termination towards the terminating network which is allocated by the MF if the media instruction from the DCSF is to terminate and originate the media; and also replace the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" when the media proxy configuration is HTTP proxy; and
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.
an existing application data channel media description in which 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 or the original application data channel media description if no media instruction received from DCSF, as well as the media description of established video, audio and bootstrap data channels.

Upon receipt of the 183 (Session Progress) or 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,

if the application data channel is accepted, the IMS AS shall notify the DCSF about the media change success and request the MF to update the media resources. Based on the response of the MF, the IMS AS shall:
1. generate and add a data channel media description in the SDP answer by using the media information allocated on the termination towards to the originating UE on the MF if the instruction from the DCSF is to terminate the media;
2. add the rejected media description and set the port number to 0 in the "m=applicaiton" line if the instruction from the DCSF is to reject the media;
3. replace the IP address represented in the "c=" line, the UDP port number in the "m=application" in the media description in the SDP answer with the media resource information on the termination towards to the originating UE allocated by the MF, if the instruction from the DCSF is to terminate and originate the media; and also replace the DC endpoint information as attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" when the media proxy configuration is HTTP proxy; and
4. delete the media description in the SDP answer if the instruction from the DCSF is to originate a new media;
and send the 183 (Session Progress) or 200 (OK) response with the modified SDP answer on the re-INVITE request to the S-CSCF towards to the originating UE after the receipt of an acknowledgement from the DCSF to the corresponding notification.
if the application data channel is rejected, the IMS AS shall notify the DCSF about the media change failure event and request the MF to release the media resources. Then, the IMS AS shall send 183 (Session Progress) or 200 (OK) response to S-CSCF after the receipt of an acknowledgement from the DCSF to the corresponding notification.

Upon receipt of a CANCEL request to the re-INVITE request, the IMS AS shall notify the DCSF about the media change cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request as per clause 9.3.2.2.1.

Upon receipt of a 4xx, 5xx or 6xx response on the re-INVITE request from the terminating network, the IMS AS shall notify the DCSF about media change failure, request the MF to release the corresponding data channel media resources and forward the response to the originating UE.

Upon receiving the re-INVITE request from the terminating network to setup data channels and the corresponding response from the originating UE, the procedure in clause 9.3.3.2.2 applies.

9.3.2.2.2.3 Closing application data channel p. 18

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.

9.3.2.2.3 MMTel session release p. 19

Upon initiation or receipt of a BYE request matching an existing MMTel session with IMS data channel, the IMS AS shall notify session release event to the DCSF and follow the call release procedure as per TS 24.229.

IMS AS shall send media resource management request to MF to release the allocated data channel media resources for this MMTel session.