Section: 4.25.2 SMF-NEF Connection Establishment
Content: When the UE performs the PDU Session establishment with PDU Session type of "Unstructured" and the subscription information corresponding to the UE requested DNN includes the "NEF Identity for NIDD" (NEF ID), then the SMF initiates a SMF-NEF Connection establishment procedure towards the NEF corresponding to the "NEF ID" for that DNN / S-NSSAI Combination. Figure 4.25.2-1: SMF-NEF Connection procedure 1. Steps 1-7 and step 9 of clause 4.3.2.2.1 for UE-requested PDU Session Establishment Procedure for non-roaming scenarios or steps 1-9 of clause 4.3.2.2.2 for UE-requested PDU Session Establishment Procedure for home-routed roaming scenarios. The (H-)SMF receives the Session Management Subscription data for the corresponding SUPI, DNN and S-NSSAI that is associated with NEF Identity for NIDD and NIDD information such GPSI and AF Identifier. 2. If the subscription information corresponding to DNN and S-NSSAI includes the "NEF Identity for NIDD" (NEF ID), the SMF shall create a PDU session towards the NEF. The SMF invokes Nnef_SMContext_Create Request (User Identity, PDU Session ID, SMF ID, NIDD information, S-NSSAI, DNN, [RDS support indication], [Small Data Rate Control parameters], [Small Data Rate Control Status], [Serving PLMN Rate Control parameters]) message towards the NEF. The RDS support indication is included if the UE capability to support Reliable Data Service (RDS) is included in the PCO in the PDU Session Establishment Request message. The SMF provides Small Data Rate Control parameters to the NEF for PDU Session, if required. The SMF provides the Small Data Rate Control Status to the NEF, if received from the AMF. If the Serving PLMN intends to enforce Serving PLMN Rate Control (see clause 5.31.14.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]) for this PDU session then the SMF shall provide Serving PLMN Rate Control parameters to NEF for limiting the rate of downlink control plane data packets. If no AF has previously performed the NIDD Configuration procedure with the NEF for the User Identity received in step 2, then the NEF initiates the NIDD Configuration procedure (see clause 4.25.3) before step 3. 3. The NEF creates an NEF PDU session Context and associates it with User Identity and PDU session ID. The NEF invokes Nnef_SMContext_Create Response (Cause, [RDS support indication], [Extended Buffering Support indication], [NIDD parameters]) towards the SMF confirming establishment of the PDU session to the NEF for the UE. If NEF supports and allows use of RDS, it includes the RDS support indication to SMF and the SMF includes it in the PCO. If NEF supports Extended Buffering, NEF includes Extended Buffering Support indication in the response and subscribes for mobility-related events with the AMF to receive an indication when the UE becomes reachable. The NIDD parameters (e.g. maximum packet size) are sent to the SMF, if available. 4. Steps 11-13 of clause 4.3.2.2.1 for UE-requested PDU Session Establishment Procedure for non-roaming scenarios or steps 13-16 of clause 4.3.2.2.2 for UE requested PDU Session Establishment Procedure for home-routed roaming scenarios.