This clause specifies the functionalities of the functional entities for IMS data channel.

An UE supporting IMS data channel has the following functionalities:

• support IMS data channel capability negotiation; and
• support bootstrap data channel and application data channel establishment and management.

Additionally, the UE supporting the IMS data channel capability and provisioned with AR communication, which is an application having IMS data channel capability, supports the following functionalities:

• support application's domain specific media capability exchange; and
• support application's domain specific media processing.

The IMS AS interacts with the DCSF and the MF or MRF. For functionalities of the IMS AS supporting IMS data channel refer to clause AC.2.2.4 of TS 23.228. For the IMS AS interaction with the Media Function (MF) refer to TS 29.176. For the IMS AS interaction with the Data Channel Signalling Function (DCSF) refer to 3GPP TS 29.175 [18].

IMS Multimedia Telephony communication service enhanced to support IMS data channel is provided after prior arrangement with the service provider. IMS Multimedia Telephony communication service enhanced to support IMS data channel is withdrawn at the user's request or for administrative reasons.

The IMS multimedia telephony communication enhanced to support the IMS data channel applications shall support data channel media specified in clause 6.2.10 of TS 26.114 in addition to MMTel media types listed in TS 22.173. The session control procedures for the different media types shall be in accordance with TS 24.229, TS 24.173, and clause 9. The usage of IMS data channel media streams in MMTel session is negotiated using the SDP offer/answer procedures defined in RFC 3264. If the received SDP offer contains IMS data channel media stream(s) and if the receiving entity does not want to use the IMS data channels, the receiving entity shall reject the offered data channel media stream(s) by setting the port number of the rejected data channel media stream(s) to zero in created SDP answer.

The MMTel service enhanced to support IMS Data Channel shall use the ICSI value defined in clause 5.1 of TS 24.173. The UE and IMS AS shall handle the ICSI value as specified in TS 24.229.

Once the bootstrap data channels have been established, if the IMS data channel applications are available, based on the IMS data channel applications list received via the established bootstrap data channel, the UE shall download through the established bootstrap data channel the IMS data channel applications. The UE shall follow the procedures in clause 9.3.2.1.3 to set up an application data channel and include in the re-INVITE request the updated SDP offer with negotiated bootstrap data channel media description, the requested application data channel media description as well as the associated data channel application binding information (provided within the "a=3gpp-req-app" SDP attribute), according to TS 23.228 and TS 26.114.

After the bootstrap data channels have been established, if the IMS AS received a re-INVITE request with an SDP offer containing application data channels media descriptions (identified by "dcmap" attribute lines containing "stream-id" parameter set to values starting at 1000 and associated "a=3gpp-req-app" attribute lines as specified in TS 26.114), the IMS AS shall notify the DCSF, may trigger the reservation or update of corresponding application data channel media resources upon the instruction from the DCSF and shall send re-INVITE request with the SDP offer containing the requested application data channel and related bootstrap data channel media descriptions according to the specific data channel application use case (e.g. P2P/P2A/P2A2P), following the procedures in TS 23.228, and clauses 9.3.2.2 and 9.3.3.2.2.