Section: 5.2.8.2 Nsmf_PDUSession Service 5.2.8.2.1 General
Content: Service description: This service operates on the PDU Sessions. The following are the key functionalities of this NF service: - (between AMF and SMF) Creation / Deletion / Modification of AMF-SMF interactions for PDU Sessions; The resource handled between AMF and SMF via Create / Update / Release SM context operations corresponds to the AMF-SMF association for a PDU Session; When the AMF has got no association with an SMF to support a PDU Session, the AMF creates such association via the Nsmf_PDUSession_CreateSMContext operation. The context created is identified via the SM Context ID. Otherwise (e.g. at hand-over between 3GPP and Non 3GPP access) the AMF uses the Nsmf_PDUSession_UpdateSMContext operation. NOTE 1: In TS 29.502[ 5G System; Session Management Services; Stage 3 ]  [36] SM Context ID is referred to as smContextRef for N11 and pduSessionRef and pduSessionUri for N16. When the UE is handed-over from an (old) AMF towards another (new) AMF, the old AMF provides the new AMF with the SMF addressing information corresponding to the AMF-SMF association related with each PDU Session of that UE. The new AMF can thus further act upon the association with the SMF via Nsmf_PDUSession_UpdateSMContext and Nsmf_PDUSession_ReleaseSMContext operations. This may take place: - at inter AMF change due to AMF planned maintenance or due to AMF failure described in clause 5.21.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]; - at inter AMF mobility in CM-CONNECTED state described in clause 4.9.1.3; - at inter AMF mobility in CM-IDLE state described in clause 4.2.2.2. - (between AMF and SMF) Passing MO Small Data from AMF to SMF in clause 4.24.1. - (between V-SMF and H-SMF) Creation / Deletion / Modification of PDU Sessions; - (between V-SMF/I-SMF and (H-)SMF) Transferring MO Small Data from V-SMF/I-SMF to (H-)SMF in clause 4.25.4. - (between V-SMF/I-SMF and (H-)SMF) Transferring MT Small Data from (H-)SMF to V-SMF/I-SMF in clause 4.24.5. Even though the V-SMF creates the PDU Session resource onto the H-SMF, each of the V-SMF and of the H-SMF needs to be able to modify a PDU Session and/or to ask for PDU Session Release. Thus, at Nsmf_PDUSession_Create, V-SMF informs the H-SMF about addressing information for its corresponding PDU Session resource, allowing H-SMF to use later on the Nsmf_PDUSession_Update and Nsmf_PDUSession_Release and Nsmf_PDUSession_StatusNotify operations. NOTE 2: The PDU Session resource in V-SMF is created when the AMF requests to create SM context of this PDU Session NOTE 3: H-SMF also informs the consumer (V-SMF) about addressing information about its PDU Session resource, but this is part of normal resource creation operation in REST and not specific to this service.