The policy related to the UE supporting the IMS data channel can be provided by the network to the UE using e.g. OMA-DM with the management objects specified in TS 24.275, ISIM with EFIMSDCI file specified in TS 31.103 or USIM with EFIMSDCI file specified in TS 31.102. When the UE is configured as specified in TS 24.275, TS 31.103 or TS 31.102 with configuration for IMS data channel allowed then the UE determines support for IMS data channel according to the configuration. If the UE is configured with both IMS_DC_configuration node and EFIMSDCI file, then the EFIMSDCI file shall take precedence. If the UE is configured with IMS_DC_configuration node specified in TS 24.275 or EFIMSDCI file specified in TS 31.103 or TS 31.102, and the DC_allowed leaf of the IMS_DC_configuration node or IMS DC Establishment Indication of the EFIMSDCI file indicates that IMS data channel is allowed, then a UE supporting IMS data channel on sending an unprotected REGISTER request shall include the media feature tag defined in RFC 5688 for supported streaming media type. For the IMS data channel capability indication, the UE shall use +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114. On receiving the 200 (OK) response to the REGISTER request, if the 200 (OK) response includes a Feature-Caps header field containing feature-capability indicator "g.3gpp.datachannel", the UE shall determine that the home network supports the IMS data channel capability as specified in TS 23.228.

If the UE is allowed to use IMS data channel, on reception of Re-REGISTER request, for user-initiated reregistration, the UE supporting IMS data channel shall include the media feature tag defined in RFC 5688 for supported streaming media type. For the IMS data channel capability indication, the UE shall use +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114. On receiving the 200 (OK) response to the Re-REGISTER request, if the 200 (OK) response includes a Feature-Caps header field containing feature-capability indicator "g.3gpp.datachannel", the UE shall determine that the home network supports the IMS data channel capability as specified in TS 23.228. The UE shall continue to indicate its IMS data channel capability as specified in the above procedure when the UE has successfully done the IMS data channel capability negotiation during IMS initial registration or re-registration. On receiving the 200 (OK) response to the REGISTER request, if the 200 (OK) response does not include a Feature-Caps header field containing feature-capability indicator "g.3gpp.datachannel",

• the UE shall not include IMS data channel capability indication in the SIP Contact and Accept-Contact header fields and IMS data channel media description in an SDP offer in further initial session setup request; and
• shall keep established data channel media of the UE's existing IMS session.

Upon generating an initial INVITE request or a re-INVITE request, the UE supporting IMS data channel and if the UE determined its home network supports the IMS data channel capability, the UE shall include the media feature tag defined in RFC 5688 for supported streaming media type in the Contact header field to the remote UE and use +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114, regardless of IMS data channel media description being part of the SDP or not. The UE may include in the initial INVITE request 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 24.173. Upon receiving an initial INVITE request or a re-INVITE request, the UE supporting IMS data channel and configured with IMS data channel is allowed shall use +sip.app-subtype="webrtc-datachannel" as specified in TS 26.114 when including the media feature tags defined in RFC 5688 for supported streaming media type in the Contact header field in the SIP response, regardless of IMS data channel media description being part of the SDP or not.