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Content for  TS 29.502  Word version:  18.6.0

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5.2.2  Service Operationsp. 16

5.2.2.1  Introductionp. 16

See Table 5.2.1-1 for an overview of the service operations supported by the Nsmf_PDUSession service.

5.2.2.2  Create SM Context service operationp. 17

5.2.2.2.1  Generalp. 17
The Create SM Context service operation shall be used to create an individual SM context, for a given PDU session, in the SMF, in the V-SMF for HR roaming scenarios, or in the I-SMF for a PDU session with an I-SMF.
It is used in the following procedures:
There shall be only one individual SM context per PDU session.
The NF Service Consumer (e.g. AMF) shall create an SM context by using the HTTP POST method as shown in Figure 5.2.2.2.1-1.
Reproduction of 3GPP TS 29.502, Fig. 5.2.2.2.1-1: SM context creation
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Step 1.
The NF Service Consumer shall send a POST request to the resource representing the SM contexts collection resource of the SMF. The content of the POST request shall contain:
  • a representation of the individual SM context resource to be created;
  • the requestType IE, if the Request type IE is received from the UE for a single access PDU session and if the request refers to an existing PDU session or an existing Emergency PDU session; the requestType IE shall not be included for a MA-PDU session establishment request; it may be included otherwise;
  • the Old PDU Session ID, if it is received from the UE (i.e. for a PDU session establishment for the SSC mode 3 operation);
  • the indication that the UE is inside or outside of the LADN (Local Area Data Network) service area, if the DNN corresponds to a LADN;
  • the perLadnDnnSnssaiInd IE, indicating that the PDU Session is subject to LADN per LADN DNN and S-NSSAI, if the AMF enforces the LADN Service Area per LADN DNN and S-NSSAI;
  • the indication that a MA-PDU session is requested if a MA-PDU session is requested to be established by the UE, or the indication that the PDU session is allowed to be upgraded to a MA-PDU session if so indicated by the UE;
  • the n3gPathSwitchSupportInd IE if the AMF supports non-3GPP access path switching while maintaining two N2 connections for non-3GPP access, the selected SMF supports non-3GPP path switching and if the UE supports non-3GPP access path switching as specified in clause 4.22.2.1 of TS 23.502;
  • the indication that the same PCF is required for the requested DNN and S-NSSAI, if it is received by the AMF from UE Subscription data in the UDM, together with the PCF ID selected by the AMF;
  • the alternative S-NSSAI, if the NF service consumer and UE support the network slice replacement and it is requested to replace the S-NSSAI with the alternative S-NSSAI (see clause 5.15.19 of TS 23.501);
  • the alternative HPLMN S-NSSAI, if the NF service consumer and UE support the network slice replacement and it is requested to replace the HPLMN S-NSSAI with the alternative HPLMN S-NSSAI for a roaming PDU session (see clause 5.15.19 of TS 23.501);
  • the anType;
  • the additionalAnType, if the UE is registered over both 3GPP and Non-3GPP accesses;
  • the cpCiotEnabled IE with the value "True", if the NF service consumer (e.g. the AMF) has verified that the CIOT feature is supported by the SMF (and for a home-routed session, that it is also supported by the H-SMF), and Control Plane CIoT 5GS Optimisation is enabled for this PDU session;
  • the cpOnlyInd IE with the value "True", if the PDU session shall only use Control Plane CIoT 5GS Optimisation;
  • the Invoke NEF indication with the value "True" for a home-routed PDU session, if the cpCiotEnabled IE is set to "True" and data delivery via NEF is selected for the PDU session;
  • a subscription for SM context status notification;
  • the servingNfId identifying the serving AMF;
  • trace control and configuration parameters, if trace is to be activated (see TS 32.422);
  • identifiers (i.e. FQDN or IP address) of N3 terminations at the W-AGF, TNGF or TWIF, if available;
  • a subscription for DDN failure notification, if the Availability after DDN failure event is subscribed by the UDM;
  • the upipSupported IE set to "true", if the UE supports User Plane Integrity Protection with EPS and if the AMF supports the related functionality.
For the UE requested PDU Session Establishment procedure in home routed roaming scenario (see clause 4.3.2.2.2 of TS 23.502), the NF Service Consumer shall provide the URI of the Nsmf_PDUSession service of the H-SMF in the hSmfUri IE and optionally the corresponding SMF ID, and may provide the URI of the Nsmf_PDUSession service of additional H-SMF(s) with the corresponding SMF ID(s). The V-SMF shall try to create the PDU session using the hSmfUri IE. If due to communication failure on the N16 interface the V-SMF does not receive any response from the H-SMF, then:
  • depending on operator policy, the V-SMF may try reaching the hSmfUri via an alternate path; or
  • if additional H-SMF URI is provided, the V-SMF may try to create the PDU session on one of the additional H-SMF(s) provided.
For a PDU session establishment with an I-SMF (see clause 4.23.5.1 of TS 23.502), the NF Service Consumer shall provide the URI of the Nsmf_PDUSession service of the SMF in the smfUri IE and optionally the corresponding SMF ID, and may provide the URI of the Nsmf_PDUSession service of additional SMF(s) with the corresponding SMF ID(s). The I-SMF shall try to create the PDU session using the smfUri IE. If due to communication failure on the N16a interface the I-SMF does not receive any response from the SMF, then:
  • depending on operator policy, the I-SMF may try reaching the smfUri via an alternate path; or
  • if additional SMF URI is provided, the I-SMF may try to create the PDU session on one of the additional SMF(s) provided.
For the UE requested PDU Session Establishment procedure, if the AMF determines that the RAT type is NB-IoT and the UE has already 2 PDU Sessions with user plane resources activated, the AMF may continue with the PDU Session establishment and include the cpCiotEnabled IE or cpOnlyInd IE with the value "True" to the SMF as specified in clause 4.3.2.2.1 of TS 23.502.
The content of the POST request may further contain:
  • the name of the AMF service to which SM context status notification are to be sent (see clause 6.5.2.2 of TS 29.500), encoded in the serviceName attribute;
  • the remote provisioning server information, if both the AMF and SMF support the Remote Provisioning of UEs in Onboarding Network procedures and the AMF received the information from AUSF for remote provisioning of the UE via user plane;
  • the Onboarding Indication, if the UE is registered for onboarding in an SNPN;
  • the indication of Notification for SM Policy Association events with the value "true" and the callback information of the PCF for the UE (i.e. the PCF for AM Policy and possibly UE Policy) to receive the notification, if both NF service consumer and the SMF support the "SPAE" feature and if the SM Policy Association Establishment and Termination events should be reported for the PDU session by the PCF for SM Policy to the PCF for the UE. See clause 4.3.2.2.1 of TS 23.502;
  • the satelliteBackhaulCat IE indicating the category of the satellite backhaul used towards the 5G AN serving the UE, if the AMF is aware of that a satellite backhaul is used towards the 5G AN;
  • the disasterRoamingInd IE set to true if the UE is registered for Disaster Roaming service;
  • the hrsboAllowedInd IE set to true if the Session Breakout for HR session in VPLMN is allowed;
  • the indication of PDU session establishment rejection together with the corresponding rejection cause, if the SMF supports the "PSER" (PDU Session Establishment Rejection) feature and the NF service consumer (i.e. the AMF) has determined that the PDU Session Establishment shall be rejected (e.g. due to the ODB configuration retrieved from the UDM).
Step 2a.
On success, "201 Created" shall be returned, the content of the POST response shall contain the representation describing the status of the request and the "Location" header shall be present and shall contain the URI of the created resource. The authority and/or deployment-specific string of the apiRoot of the created resource URI may differ from the authority and/or deployment-specific string of the apiRoot of the request URI received in the POST request.
If the requestType IE was received in the request and set to EXISTING_PDU_SESSION or EXISTING_EMERGENCY_PDU_SESSION (i.e. indicating that this is a UE request for an existing PDU session or an existing emergency PDU session), the SMF shall identify the existing PDU session or emergency PDU session based on the PDU Session ID; in this case, the SMF shall not create a new SM context but instead update the existing SM context and provide the representation of the updated SM context in the "201 Created" response to the NF Service Consumer.
The POST request shall be considered as colliding with an existing SM context if:
  • this is a request to establish a new PDU session, i.e.:
    • the RequestType IE is present in the request and set to INITIAL_REQUEST or INITIAL_EMERGENCY_REQUEST (e.g. single access PDU session establishment request);
    • the RequestType IE and the maRequestInd IE are both absent in the request (e.g. EPS to 5GS mobility); or
    • the maRequestInd IE is present in the request (i.e. MA-PDU session establishment request) and the access type indicated in the request corresponds to the access type of the existing SM context.
and either of the following conditions is met:
  • this is a request to establish a non-emergency PDU session and the request includes the same SUPI and the same PDU Session ID as for an existing SM context; or
  • this is a request to establish an emergency PDU session and the request includes the same SUPI, or PEI for an emergency registered UE without a UICC or without an authenticated SUPI, as for an existing SM context for an emergency PDU session.
A POST request that collides with an existing SM context shall be treated as a request for a new SM context. Before creating the new SM context, the SMF should delete the existing SM context locally and any associated resources in the UPF, PCF, CHF, and UDM. If the UP connection of the existing PDU session is active, the SMF should also request (R)AN to release associated resources. See also clause 5.2.3.3.1 for the handling of requests which collide with an existing SM context. If the smContextStatusUri of the existing SM context differs from the smContextStatusUri received in the POST request, the SMF shall also send an SM context status notification (see clause 5.2.2.5) targeting the smContextStatusUri of the existing SM context to notify the release of the existing SM context. For a HR PDU session, if the H-SMF URI in the request is different from the H-SMF URI of the existing PDU session, the V-SMF should also delete the existing PDU session in the H-SMF by invoking the Release service operation (see clause 5.2.2.9). For a PDU session with an I-SMF, if the SMF URI in the request is different from the SMF URI of the existing PDU session, the I-SMF should also delete the existing PDU session in the SMF by invoking the Release service operation (see clause 5.2.2.9).
If the requestType IE was received in the request and indicates this is a request for a new PDU session (i.e. INITIAL_REQUEST) and if the Old PDU Session ID was also included in the request, the SMF shall identify the existing PDU session to release and to which the new PDU session establishment relates, based on the Old PDU Session ID.
If no GPSI IE is provided in the request, e.g. for a PDU session moved from another access or another system, and the SMF knows that a GPSI is already associated with the PDU session (or a GPSI is received from h-SMF for a HR PDU session), the SMF shall include the GPSI in the response.
If the indication of Notification for SM Policy Association events was received with the value "true" together with the callback information of the PCF for the UE in the request and SM Policy Association is to be established for the PDU session, the SMF shall provide the callback information of the PCF for the UE to the PCF for SM Policy during SM Policy Association Establishment.
Step 2b.
If the request does not include the "UE presence in LADN service area" indication and the SMF determines that the DNN corresponds to a LADN, then the SMF shall consider that the UE is outside of the LADN service area. The SMF shall reject the request if the UE is outside of the LADN service area.
On failure, or redirection during a UE requested PDU Session Establishment, one of the HTTP status code listed in Table 6.1.3.2.3.1-3 shall be returned. For a 4xx/5xx response, the message body shall contain an SmContextCreateError structure, including:
  • a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.2.3.1-3;
  • N1 SM information (PDU Session Reject), if the request included N1 SM information, except if the error prevents the SMF from generating a response to the UE (e.g. invalid request format).
For the UE requested PDU Session Establishment, the SMF shall reject the request with "EXCEEDED_SLICE_DATA_RATE" application error if the SMF receives from the PCF that the maximum bit rate per S-NSSAI is exceeded, or with "EXCEEDED_UE_SLICE_DATA_RATE" application error if the SMF receives from the PCF that the maximum bit rate per S-NSSAI per UE is exceeded.
For the UE requested PDU Session Establishment, the SMF shall directly reject the request if the SMF supports the "PSER" feature and it has received the indication of PDU Session Establishment Rejection from the AMF in the Create SM Context request.
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5.2.2.2.2  EPS to 5GS Idle mode mobility using N26 interface (with or without data forwarding)p. 21
The NF Service Consumer (e.g. AMF) shall request the SMF to move a UE EPS PDN connection to 5GS using N26 interface, as follows.
Reproduction of 3GPP TS 29.502, Fig. 5.2.2.2.2-1: EPS to 5GS Idle mode mobility using N26 interface
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Step 1.
The NF Service Consumer shall send a POST request towards the SMF (+PGW-C) of each UE EPS PDN connection, as specified in clause 5.2.2.2.1, with the following additional information:
  • UE EPS PDN connection, including the EPS bearer contexts, received from the MME, representing the individual SM context resource to be created;
  • the pduSessionsActivateList attribute, including the PDU Session ID of all the PDU session(s) to be re-activated;
  • the epsBearerCtxStatus attribute, indicating the status of all the EPS bearer contexts in the UE, if corresponding information is received in the Registration Request from the UE;
  • the dlDataWaitingInd attribute, indicating that DL data buffered in EPS needs to be forwarded to the UE, if such indication is present in the Context Response received from the MME.
Step 2a.
Upon receipt of such a request, if:
  • a corresponding PDU session is found based on the EPS bearer contexts (after invoking a Create service operation towards the H-SMF for a Home Routed PDU session, or towards the SMF for a PDU session with an I-SMF);
  • the default EPS bearer context of the corresponding PDU session is not reported as inactive by the UE in the epsBearerCtxStatus attribute, if received; and
  • it is possible to proceed with moving the PDN connection to 5GS,
then the SMF shall return a 201 Created response including the following information:
  • PDU Session ID corresponding to the default EPS bearer ID of the EPS PDN connection;
  • S-NSSAI assigned to the PDU session; in home routed roaming case, the S-NSSAI for home PLMN shall be returned;
  • the allocatedEbiList attribute, containing the EBI(s) allocated to the PDU session;
and, if the PDU session that is derived by the SMF based on the EPS bearer contexts was requested to be re-activated, i.e. if the PDU Session ID was present in the pduSessionsActivateList,or if DL data buffered in EPS needs to be forwarded to the UE:
  • the upCnxState attribute set to ACTIVATING;
  • N2 SM information to request the 5G-AN to assign resources to the PDU session (see PDU Session Resource Setup Request Transfer IE in clause 9.3.4.1 of TS 38.413), including (among others) the transport layer address and tunnel endpoint of the uplink termination point for the user plane data for this PDU session (i.e. UPF's GTP-U F-TEID for uplink traffic).
The "Location" header shall be present in the POST response and shall contain the URI of the created SM context resource.
If the epsBearerCtxStatus attribute is received in the request, the SMF shall check whether some EPS bearer(s) of the corresponding PDU session have been deleted by the UE but not notified to the EPS, and if so, the SMF shall release these EPS bearers, corresponding QoS rules and QoS flow level parameters locally, as specified in clause 4.11.1.3.3 of TS 23.502.
The NF Service Consumer (e.g. AMF) shall store the association of the PDU Session ID and the SMF ID, and store the allocated EBI(s) associated to the PDU Session ID.
Step 2b.
Same as step 2b of Figure 5.2.2.2.1-1. Steps 3 to 4 are skipped in this case.
If the SMF determines that seamless session continuity from EPS to 5GS is not supported for the PDU session, the SMF shall set the "cause" attribute in the ProblemDetails structure to "NO_EPS_5GS_CONTINUITY".
If the default EPS bearer context of the PDU session is reported as inactive by the UE in the epsBearerCtxStatus attribute, the SMF shall set the "cause" attribute in the ProblemDetails structure to "DEFAULT_EPS_BEARER_INACTIVE".
Step 3.
Same as step 3 of Figure 5.2.2.3.2.2-1, if the SMF returned a 201 Created response with the upConnectionState set to ACTIVATING and N2 SM Information,
Step 4.
Same as step 4 of Figure 5.2.2.3.2.2-1. During an EPS to 5GS Idle mode mobility using N26 interface with data forwarding (see clause 4.11.1.3.3A of TS 23.502), the 200 OK response shall additionally contain the CN tunnel information for data forwarding from EPS, i.e. the forwardingFTeid attribute or the forwarding bearer contexts to be sent to the MME in the Context Acknowledge, based on the association between the EPS bearer ID(s) and QFI(s) for the QoS flow(s).
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5.2.2.2.3  EPS to 5GS Handover Preparation using N26 interfacep. 23
The NF Service Consumer (e.g. AMF) shall request the SMF to handover a UE EPS PDN connection to 5GS using N26 interface, as follows.
Reproduction of 3GPP TS 29.502, Fig. 5.2.2.2.3-1: EPS to 5GS handover using N26 interface
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Step 1.
The NF Service Consumer shall send a POST request, as specified in clause 5.2.2.2.1, with the following additional information:
  • UE EPS PDN connection, including the EPS bearer contexts, representing the individual SM context resource to be created;
  • hoState attribute set to PREPARING (see clause 5.2.2.3.4.1);
  • the indication of whether direct or indirect DL data forwarding applies;
  • targetId identifying the target RAN Node ID and TAI based on the Target ID IE received in the Forward Relocation Request message from the source MME.
Step 2a.
Upon receipt of such a request, if a corresponding PDU session is found based on the EPS bearer contexts (after invoking a Create service operation towards the H-SMF, for a Home Routed PDU session) and it is possible to proceed with handing over the PDN connection to 5GS, the SMF shall return a 201 Created response including the following information:
  • hoState attribute set to PREPARING and N2 SM information to request the target 5G-AN to assign resources to the PDU session, as specified in step 2 of Figure 5.2.2.3.4.2-1; if the SMF was indicated in step 1 that direct data forwarding is applicable, the SMF shall include an indication that a direct forwarding path is available in the N2 SM information;
  • PDU Session ID corresponding to the default EPS bearer ID of the EPS PDN connection;
  • S-NSSAI assigned to the PDU session; in home routed roaming case, the S-NSSAI for home PLMN shall be returned;
  • allocatedEbiList, containing the EBI(s) allocated to the PDU session;
  • optional udmGroupId, containing the identity of the UDM group serving the UE, to facilitate the UDM selection at the target AMF;
  • optional pcfGroupId, containing the identity of the PCF group for Session Management Policy for the PDU session, to facilitate the PCF selection at the target AMF.
The "Location" header shall be present in the POST response and shall contain the URI of the created SM context resource.
The NF Service Consumer (e.g. AMF) shall store the association of the PDU Session ID and the SMF ID, and store the allocated EBI(s) associated to the PDU Session ID.
Step 2b.
Same as step 2b of Figure 5.2.2.2.1-1 with the following additions. Steps 3 and 4 of Figure 5.2.2.3.8.2-1 are skipped in this case.
If the SMF determines that seamless session continuity from EPS to 5GS is not supported for the PDU session, the SMF shall set the "cause" attribute in the ProblemDetails structure to "NO_EPS_5GS_CONTINUITY".
When receiving a 4xx/5xx response from the SMF, the NF service consumer (e.g. the AMF) shall regard the hoState of the SM Context to be NONE.
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