Content for  TS 23.228  Word version:  19.4.0

defined in TS 26.114. When the originating DCMTSI UE initiates an IMS DC session to the terminating MTSI UE, a bootstrap data channel is set up between the originating DCMTSI UE and the originating network (i.e. DCSF and MF) and an MMTEL session for the other media (e.g. audio, video, any MMTEL media other than data channel) may be set up with the terminating side based on the SDP response from the terminating MTSI UE. This is described in clause AC.7.9.1. The originating DCMTSI UE may initiate an application data channel associated with the MMTEL session between the DCMTSI UE and the MTSI UE (e.g. for real-time screen sharing). The data channel media sent from the originating DCMTSI UE is transcoded to MMTEL media and transferred to the terminating MTSI UE via the associated RTP stream; equally, the MMTEL media sent from the terminating MTSI UE is transcoded to data channel media and transferred to the originating DCMTSI UE via the associated application data channel stream. This is described in clause AC.7.9.2. A DCMTSI UE that requires interworking with an MTSI UE, may initiate an application data channel setup with the DC AS for data channel application configured to support interworking with an MTSI UE. The DC AS subscribes to the IMS AS to be notified about any application data channel event for data channel applications that require interworking with an MTSI UE. This is described in clause AC.7.9.3. A DC AS may initiate data channel with a terminating DCMTSI UE when it requires interworking with an MTSI UE that originated the IMS session. The DC AS subscribes to the IMS AS to be notified when any IMS session is established between any MTSI UE and the DCMTSI UE as the callee. In this case the callee is configured as an interworking provider (e.g. customer service centre). This is described in clause AC.7.9.4.

Figure AC.7.9.1-1 depicts a signalling flow diagram for establishing a bootstrap data channel when the originating DCMTSI UE initiates an IMS DC session to the terminating MTSI UE. In Figure AC.7.9.1-1, the procedure starts with the INVITE including SDP offer which includes audio and data channel media and represent the minimum SDP offer to initiate this procedure, however it is not limited only for that media (e.g. the video offer may be included).

Figure AC.7.9.2-1 depicts a signalling flow diagram for establishing the application data channel when the originating DCMTSI UE initiates an IMS DC session to the terminating MTSI UE, providing interworking of application data channel to MTSI UE via MF. This procedure enables the transcoding to be performed by the MF, upon instructions by the DCSF, transcode between the data channel media and the MMTEL media such as audio and video, e.g. Real-time Screen Sharing.