Section: 4.2.10.1 UE triggered N3 data transfer establishment procedure
Content: If UE and AMF successfully negotiate N3 data transfer in addition to Control Plane CIoT 5GS Optimisation based on the Preferred and Supported Network Behaviour as defined in clause 5.31.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2], then the UE may, e.g. based on the amount of data to be transferred in uplink, initiate N3 data transfer establishment procedure for any PDU session for which Control Plane Only Indicator was not included. The UE triggered N3 data transfer establishment procedure may be initiated by the UE in CM-IDLE or CM-CONNECTED state and follows the UE triggered Service Request procedure as defined in clause 4.2.3.2 with the following differences. Step 1. The UE includes in the AN message a Service Request for Control Plane CIoT 5GS Optimisation (List Of PDU Sessions To Be Activated, List Of Allowed PDU Sessions, security parameters, PDU Session status, [NAS message container])). The List Of PDU Sessions To Be Activated is provided by UE when the UE wants to activate user plane resources for the PDU Session(s). The UE shall not include PDU sessions for which Control Plane Only Indicator was received in the List Of PDU Sessions To Be Activated. If the UE is camping on NB-IoT, the UE shall construct the List of PDU Sessions To Be Activated to not exceed 2 PDU session(s) with active user plane resources. If this procedure is triggered for paging response and the UE has at the same time some user data to be transferred, the UE may decide to request N3 data transfer establishment for one of more PDU sessions. The UE indicates this in the List Of PDU Sessions To Be Activated. Otherwise the UE does not identify any PDU Session in the List Of PDU Sessions To Be Activated. Step 4 or 5a. Upon reception of Nsmf_PDUSession_UpdateSMContext Request or after SMF initiated SM Policy Association Modification, based on UE request and local policies, the SMF decides whether to establish N3 data transfer for the PDU session. The SMF shall not decide to establish N3 data transfer for a PDU session for which Control Plane Only Inidcator was received. Step 11. The SMF indicates in Nsmf_PDUSession_UpdateSMContext Response whether to establish N3 data transfer, i.e. activate Data Radio Bearer and N3 tunnel, for the PDU session. Step 12. If the RAT type is NB-IoT, the AMF shall ensure that number of PDU Sessions with active user plane resources does not exceed 2. If the AMF decides to not include a PDU Session to be activated in the N2 message, the AMF indicates this to the SMF in step 15 Nsmf_PDUSession_UpdateSMContext Request in the List of PDU Sessions that failed to be established with the failure cause given in the N2 SM information element. The AMF includes a NAS service accept for Control Plane CIoT 5GS Optimisation containing information on the PDU sessions with established N3 data transfer, based on the request(s) from the SMF(s) in step 11. The network starts using N3 bearers for all DL data on this PDU session. Control Plane CIoT 5GS Optimisation is considered enabled for data transfer for all PDU sessions without established N3 data transfer. Step 13. The UE starts using N3 bearears for all UL data on this PDU session.