5.2.2 Service Operations

29.5183GPP5G SystemAccess and Mobility Management ServicesRelease 18Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.2.2.1 Introduction

The Namf_Communication service supports following service operations:

– UEContextTransfer

– RegistrationStatusUpdate

– N1N2MessageTransfer (UE Specific)

– N1N2TransferFailureNotification (UE Specific)

– N1N2MessageSubscribe (UE Specific)

– N1N2MessageUnsubscribe (UE Specific)

– N1MessageNotify (UE Specific)

– N2InfoNotify (UE Specific)

– NonUeN2MessageTransfer

– NonUeN2InfoSubscribe

– NonUeN2INfoUnsubscribe

– N2InfoNotify

– EBIAssignment

– CreateUEContext

– ReleaseUEContext

– RelocateUEContext

– CancelRelocateUEContext

– AMFStatusChangeSubscribe

– AMFStatusChangeUnsubscribe

– AMFStatusChangeNotify

5.2.2.2 UE Context Operations

5.2.2.2.1 UEContextTransfer

5.2.2.2.1.1 General

The UEContextTransfer service operation is used during the following procedure:

– General Registration procedure (see 3GPP TS 23.502 [3], clause 4.2.2.2.2)

– Registration with Onboarding SNPN (see 3GPP TS 23.502 [3], clause 4.2.2.2.4)

The UEContextTransfer service operation is invoked by a NF Service Consumer, e.g. a target AMF, towards the AMF (acting as source AMF), when the target AMF receives a Registration Request with the UE’s 5G-GUTI included and the serving AMF has changed since last registration, to retrieve the UE Context, e.g. the UE’s SUPI and MM Context, in the source AMF.

The NF Service Consumer (e.g. the target AMF) shall retrieve the UE Context by invoking the "transfer" custom method on the URI of an "Individual ueContext" resource identified by UE’s 5G-GUTI, see clause 6.1.3.2.4. See also Figure 5.2.2.2.1.1-1.

Figure 5.2.2.2.1.1-1 UE Context Transfer

1. The NF Service Consumer, e.g. target AMF, shall send a HTTP POST request to invoke "transfer" custom method on an "Individual ueContext" resource URI. The payload of the request shall be an object of "UeContextTranferReqData" data type.

If UE Context Transfer is triggered by UE initial registration, mobility registration, disaster roaming initial registration or disaster roaming mobility registration, the NF Service Consumer, e.g. target AMF, shall set the reason attribute to "INIT_REG" or "MOBI_REG" and include the integrity protected registration request message which triggers the UE context transfer in the payload.

2a. On success:

– if the reason attribute is "INIT_REG" and integrity check is successful, the (source) AMF shall respond with the status code "200 OK". The payload of the response shall be an object of "UeContextTransferRspData" data type, containing:

case a) the representation of the requested UE Context as follows:

– without PDU Session Contexts associated to the access type indicated in the request by the NF Service Consumer (e.g. target AMF); and

– with PDU Session Contexts associated to the other access type, if the UE is registered for the other access type in the (source) AMF, unless the source AMF determines based on the PLMN ID or SNPN ID of the (target) AMF that there is no possibility for relocating the N2 interface for non-3GPP access to the (target) AMF;

case b) the representation of the requested UE Context only containing the "supi" attribute, if the UE is registered in a different access type in the (source) AMF and the source AMF determines based on the PLMN ID of the (target) AMF that there is no possibility for relocating the N2 interface to the (target) AMF.

– If the reason attribute is "MOBI_REG" and integrity check is successful, the (source) AMF shall respond with the status code "200 OK". The payload of the response shall be an object of "UeContextTransferRspData" data type, containing:

a) the representation of the complete UE Context including available MM and PDU Session Contexts. The source AMF shall transfer the complete UE context including both access types if the UE is registered for both 3GPP and non-3GPP accesses and if the target PLMN is the same as the source PLMN; or

b) the representation of the requested UE Context including the available MM and PDU Session Contexts for the 3GPP access type, if the UE is registered for both 3GPP and non-3GPP accesses in the (source) AMF and the source AMF determines based on the PLMN ID or SNPN ID of the (target) AMF that there is no possibility for relocating the N2 interface for non-3GPP access to the (target) AMF.

NOTE: The source AMF can determine that it is not possible to relocate the N2 interface to the target AMF when both AMFs pertain to different PLMNs or SNPNs.

The UE context shall contain trace control and configuration parameters, if signalling based trace has been activated (see 3GPP TS 32.422 [30]).

The NF Service Consumer, e.g. target AMF, starts tracing according to the received trace control and configuration parameters, if trace data is received in the UE context indicating that signalling based trace has been activated. Once the NF Service Consumer receives subscription data, trace requirements received from the UDM supersedes the trace requirements received from the AMF.

The UE context shall contain analytics subscription parameters, if the (source) AMF has created analytics subscription(s) towards NWDAF related to the UE (see clause 5.2.2.2.2 of 3GPP TS 23.502 [3]). The NF Service Consumer, e.g. target AMF, may take over the analytics subscription(s).

The UE context shall contain event subscriptions information in the following cases:

a) Any NF Service Consumer has subscribed for UE specific event; and/or

b) Any NF Service Consumer has subscribed for UE group specific events to which the UE belongs. In this case the event subscriptions provided in the UE context shall contain the event details applicable to this specific UE in the group (e.g maxReports in options IE).

The NF Service Consumer, e.g. target AMF, shall:

– in case a) create event subscriptions for the UE specific events;

– in case b) create event subscriptions for the group Id if there are no existing event subscriptions for that group Id, subscription change notification URI (subsChangeNotifyUri) and the subscription change notification correlation Id (subsChangeNotifyCorrelationId). If there is already an existing event subscription for the group Id, and for the given subscription change notification URI (subsChangeNotifyUri) and subscription change notification correlation Id (subsChangeNotifyCorrelationId), then an event subscription shall not be created at the NF Service Consumer. The individual UE specific event details (e.g maxReports in options IE) within that group shall be taken into account.

– for both the cases, for each created event subscription, allocate a new subscription Id, if necessary (see clause 6.5.2 of 3GPP TS 29.500 [4]), and if allocated, send the new subscription Id to the notification endpoint for informing the subscription Id creation, along with the notification correlation Id for the subscription Id change. If the UEContextTransfer service operation is performed towards the old AMF as part of the EPS to 5GS mobility registration procedure using N26 interface (see clause 4.11.1.3.3 of 3GPP TS 23.502 [3]), the target AMF may also initiate event subscription synchronization procedure with UDM, as specified in clause 5.3.2.4.2, when both the target AMF and the UDM support the "ESSYNC" feature.

NOTE: Subscription Id can be reused if the mobility is between AMFs of same AMF Set.

If the UE context being transferred from the source AMF is the last UE context that belongs to a UE group Id related subscription, then the source AMF shall not delete the UE group Id related subscription until the expiry of that event subscription (see clause 5.3.2.2.2).

The source AMF shall not transfer those PDU sessions which are not supported by the target AMF, e.g. the MA-PDU sessions shall not be transferred if the target AMF does not support ATSSS.

The UE context shall contain SNPN Onboarding indication, if the UE is registered for onboarding in an SNPN as described in clause 4.2.2.2.4 of 3GPP TS 23.502 [3]. The NF Service Consumer, i.e. target AMF, may start an implementation specific timer to deregister the onboarding registered UE, i.e. if the received UE context contains SNPN Onboarding indication.2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.4.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.3.2.4.4.2-2.

5.2.2.2.1.2 Retrieve UE Context after successful UE authentication

When a successful UE authentication has been performed after a previous integrity check failure, the NF service consumer (e.g. the target AMF) shall retrieve the UE context by invoking "transfer" service operation on the URI of the "Individual ueContext" resource identified by UE’s SUPI. The same requirements in clause 5.2.2.2.1.1 shall be applied with following modifications:

1. Same as step 1 of figure 5.2.2.2.1.1-1, with following differences:

– The {ueContextId} in the URI shall be composed using UE’s SUPI, and

– The "reason" attribute in request body shall be set to "MOBI_REG_UE_VALIDATED", and

– The request body shall not include registration request message from UE.

2. Same as step 2a of figure 5.2.2.2.1.1-1, with following differences:

– The (source) AMF shall skip integrity check and shall respond with the status code "200 OK "with the UE Context excluding SeafData and including available PDU Session Contexts

5.2.2.2.2 RegistrationStatusUpdate

5.2.2.2.2.1 General

The RegistrationStatusUpdate service operation is used during the following procedure:

– General Registration procedure (see 3GPP TS 23.502 [3], clause 4.2.2.2.2)

– Registration with AMF re-allocation procedure (see 3GPP TS 23.502 [3], clause 4.2.2.2.3)

The RegistrationStatusUpdate service operation is invoked by a NF Service Consumer, e.g. the target AMF, towards the NF Service Producer, i.e. the source AMF, to update the status of UE registration at the target AMF, thereby indicating the result of previous UE Context transfer for a given UE (see clause 5.2.2.2.1.1).

The target AMF shall update the NF Service Producer (i.e. source AMF) with the status of the UE registration at the target AMF due to a previous UE Context transfer. The NF Service Consumer (e.g. target AMF) shall use the HTTP method POST to invoke the "transfer-update" custom operation on the URI of an "Individual ueContext" resource, see clause 6.1.3.2.4. See also Figure 5.2.2.2.2.1-1.

Figure 5.2.2.2.2.1-1 Registration Status Update

1. The NF service consumer (e.g. target AMF), shall send a POST request to invoke the "transfer-update" custom operation on the URI of an "Individual ueContext" resource, to update the source AMF with the status of the UE registration at the target AMF. The UE’s 5G-GUTI is included as the UE identity.

The request payload shall include the transferStatus attribute set to "TRANSFERRED" if the UE context transfer was completed successfully (including the case where only the supi was transferred to the target AMF during the UE context transfer procedure) or to "NOT_TRANSFERRED" otherwise.

If any network slice(s) become no longer available and there are PDU Session(s) associated with them, the target AMF shall include these PDU session(s) in the toReleaseSessionList attribute in the payload. If the continuity of the PDU Session(s) cannot be supported between networks (e.g. SNPN-SNPN mobility, inter-PLMN mobility where no HR agreement exists), the target AMF shall include these PDU session(s) with release cause in the toReleaseSessionInfo attribute in the payload.

If the target AMF selects a new PCF for AM Policy and/or UE policy other than the one which was included in the UeContext by the old AMF, the target AMF shall set pcfReselectedInd to true.

NOTE: AMF selects the same PCF instance for AM policy and for UE policy, as described in clause 6.3.7.1, 3GPP TS 23.501 [2].

The NF service consumer shall include the smfChangeInfoList attribute including the UE’s PDU Session ID(s) for which the I-SMF or V-SMF has been changed or removed, if any, with for each such PDU session, the related smfChangeIndication attribute set to "CHANGED" or "REMOVED", if the I-SMF or V-SMF is changed or removed respectively.

If the target AMF receives analytics subscription parameters from the source AMF, and one or more analytics subscription(s) are not taken over by the target AMF, the target AMF shall include these analytics subscription(s) in the analyticsNotUsedList IE. The source AMF may unsubscribe the analytics subscriptions included in analyticsNotUsedList IE for the UE.

Once the update is received, the source AMF shall:

– remove the individual ueContext resource and release any PDU session(s) in the toReleaseSessionList attribute, if the transferStatus attribute included in the POST request body is set to "TRANSFERRED" and if the source AMF transferred the complete UE Context including all MM contexts and PDU Session Contexts. The source AMF may choose to start a timer to supervise the release of the UE context resource and may keep the individual ueContext resource until the timer expires. If the pcfReselectedInd is set to true, the source AMF shall terminate the AM Policy Association and/or the UE Policy Association that the source AMF has to the old PCF.

– keep the UE context only including the MM context and PDU session(s) associated to the non-3GPP access, if the transferStatus attribute included in the POST request body is set to " TRANSFERRED" and if the source AMF did not transfer the MM context and PDU Session Contexts for the non-3GPP access type; the AMF shall release any PDU session(s) in the toReleaseSessionList attribute. The source AMF may choose to start a timer and keep the MM context and PDU session(s) associated to the 3GPP access until the timer expires.

– keep the UE Context as if the context transfer procedure had not happened if the transferStatus attribute included in the POST request body is set to "NOT_TRANSFERRED".

2a. On Success: The source AMF shall respond with the status code "200 OK" if the request is accepted. If the smfChangeInfoList attribute was received in the request, the source AMF shall release the SM context at the I-SMF or V-SMF only, for all the PDU sessions listed in the smfChangeInfoList attribute with the smfChangeIndication attribute set to "CHANGED" or "REMOVED".

If some PDU sessions are not supported by the target AMF and thus not transferred to the target AMF, the source AMF shall release these PDU sessions after this step.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.5.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.3.2.4.5.2-2, where applicable.

5.2.2.2.3 CreateUEContext

5.2.2.2.3.1 General

The CreateUEContext service operation is used during the following procedure:

– Inter NG-RAN node N2 based handover (see 3GPP TS 23.502 [3], clause 4.9.1.3, and clause 4.23.7)

The CreateUEContext service operation is invoked by a NF Service Consumer, e.g. a source AMF, towards the AMF (acting as target AMF), when the source AMF can’t serve the UE and selects the target AMF during the handover procedure, to create the UE Context in the target AMF.

The NF Service Consumer (e.g. the source AMF) shall create the UE Context by using the HTTP PUT method with the URI of the "Individual UeContext" resource (See clause 6.1.3.2.3.1). See also Figure 5.2.2.2.3.1-1.

Figure 5.2.2.2.3.1-1 Create UE Context

1. The NF Service Consumer, e.g. source AMF, shall send a PUT request, to create the ueContext in the target AMF. The payload body of the PUT request shall contain a UeContextCreateData structure, including a N2 Information Notification callback URI.

The UE context shall contain trace control and configuration parameters, if signalling based trace has been activated (see 3GPP TS 32.422 [30]).

The source AMF shall transfer the complete UE context including both access types if the UE is registered for both 3GPP and non-3GPP accesses and if the target PLMN is the same as the source PLMN.

The source AMF shall transfer only UE context for 3GPP access if the source AMF determines there is no possibility for relocating the N2 interface for non-3GPP access to the (target) AMF, e.g. when the target AMF is in another PLMN.

For a UE supporting 5G-SRVCC, the NF Service Consumer (i.e. AMF) shall include the Mobile Station Classmark 2, STN-SR, C-MSISDN and Supported Codec List in the request, if available, as specified in 3GPP TS 23.502 [3].

The UE context shall contain analytics subscription parameters, if the (source) AMF has created analytics subscription(s) towards NWDAF related to the UE (see clause 5.2.2.2.11 of 3GPP TS 23.502 [3]). The NF service producer, e.g. target AMF, may take over the analytics subscription(s).

The UE context shall contain SNPN Onboarding indication and the target AMF shall support SNPN Onboarding, if the UE is registered for onboarding in an SNPN as described in clause 4.2.2.2.4 of 3GPP TS 23.502 [3].

2a. On success, the target AMF shall respond with the status code "201 Created" if the request is accepted, together with a HTTP Location header to provide the location of a newly created resource. The payload body of the PUT response shall contain the representation of the created UE Context. If the target AMF selects a new PCF for AM Policy other than the one which was included in the UeContext by the old AMF, the target AMF shall set pcfReselectedInd to true. If the pcfReselectedInd is set to true, the source AMF shall terminate the AM Policy Association to the old PCF.

The target AMF starts tracing according to the received trace control and configuration parameters, if trace data is received in the UE context indicating that signalling based trace has been activated. Once the AMF receives subscription data, trace requirements received from the UDM supersedes the trace requirements received from the NF Service Consumer.

The UE context shall contain event subscriptions information in the following cases:

a) Any NF Service Consumer has subscribed for UE specific event; and/or

The target AMF shall:

– in case a) create event subscriptions for the UE specific events;

– in case b) create event subscriptions for the group Id if there are no existing event subscriptions for that group Id, subscription change notification URI (subsChangeNotifyUri) and the subscription change notification correlation Id (subsChangeNotifyCorrelationId). If there is already an existing event subscription for the group Id and for the given subscription change notification URI (subsChangeNotifyUri) and subscription Id change notification correlation Id (subsChangeNotifyCorrelationId), then an event subscription shall not be created at the target AMF. The individual UE specific event details (e.g maxReports in options IE) within that group shall be taken into account.

– for both the cases, for each created event subscription, allocate a new subscription Id, if necessary (see clause 6.5.2 of 3GPP TS 29.500 [4]), and if allocated send the new subscription Id to the notification endpoint for informing the subscription Id creation, along with the notification correlation Id for the subscription Id change.

NOTE: Subscription Id can be reused if the mobility is between AMFs of same AMF Set.

If the UE context being transferred from the NF service consumer (e.g. source AMF) is the last UE context that belongs to a UE group Id related subscription, then the NF service consumer (e.g. source AMF) shall not delete the UE group Id related subscription until the expiry of that event subscription (see clause 5.3.2.2.2).

If the target AMF receives SNPN Onboarding indication from the source AMF, the target AMF may start an implementation specific timer to deregister the onboarding registered UE, i.e. if the received UE context contains SNPN Onboarding indication.

The source AMF shall:release those PDU sessions not supported by the target AMF and thus not transferred to the target AMF.

2b. On failure or redirection, 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 a UeContextCreateError structure, including:

– a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.3.2.3.1-3. The cause in the error attribute shall be set to HANDOVER_FAILURE, if all of the PDU sessions are failed, e.g. no response from the SMF within a maximum wait timer;

– NgAPCause, if available;

– N2 information carrying the Target to Source Failure Transparent Container, if this information has been received from the target NG-RAN and if the source AMF supports the NPN feature.

5.2.2.2.3.2 Create UE Context with AMF Relocation

During inter-PLMN N2 Handover, the initial AMF may relocate the UE context to a target AMF (e.g. due to slices cannot be served by initial AMF). This clause describes the procedure for this scenario.

Figure 5.2.2.2.3.2-1 Create UE Context with AMF Relocation

Same requirement of clause 5.2.2.2.3.1 applies, with following modifications:

1. Same as step 1 of clause 5.2.2.2.3.1.

2. The initial AMF selects a target AMF and perform CreateUeContext procedure (see clause 5.2.2.2.3.1).

– the request body shall include the information received from the source AMF in step 1, including the serving network, the supported features, etc.

– if the received serving network (from the source AMF) is different from the PLMN of the target AMF, the resource URI in the Location header in 201 Create response shall contain the inter-PLMN API Root.

3a. Same as step 2a of clause 5.2.2.2.3.1, with following modifications:

– the request body shall contain the UE Context and other information received from the target AMF in step 2.

– the Location header shall contain the resource URI received in the "201 Created" response from target AMF in step 2.

– the initial AMF shall insert a 3gpp-Sbi-Producer-Id header indicating the target AMF.

3b. Same as step 2b of clause 5.2.2.2.3.1.

5.2.2.2.4 ReleaseUEContext

5.2.2.2.4.1 General

The ReleaseUEContext service operation is used during the following procedure:

– Inter NG-RAN node N2 based handover, Cancel procedure (see 3GPP TS 23.502 [3], clause 4.9.1.4)

The ReleaseUEContext service operation is invoked by a NF Service Consumer, e.g. a source AMF, towards the AMF (acting as target AMF), when the source AMF receives the Handover Cancel from the 5G-AN during the handover procedure, to release the UE Context in the target AMF.

The NF Service Consumer (e.g. the source AMF) shall release the UE Context by using the HTTP "release" custom operation with the URI of the "Individual UeContext" resource (See clause 6.1.3.2.4.2). See also Figure 5.2.2.2.4.1-1.

Figure 5.2.2.2.4.1-1 Release UE Context

1. The NF Service Consumer, e.g. source AMF, shall send a POST request, to release the ueContext in the target AMF. The payload body of the POST request shall contain any data that needs to be passed to the target AMF.

2a. On success, the target AMF shall return "204 No Content" with an empty payload body in the POST response.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.2.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.2.4.2.2-2.

5.2.2.2.5 RelocateUEContext

5.2.2.2.5.1 General

The RelocateUEContext service operation is used during the following procedure:

– EPS to 5GS handover using N26 interface with AMF re-allocation (see 3GPP TS 23.502 [3], clause 4.11.1.2.2).

The RelocateUEContext service operation is invoked by a NF Service Consumer, e.g. an initial AMF, towards the AMF (acting as target AMF), during an EPS to 5GS handover with AMF re-allocation, to relocate the UE Context in the target AMF.

The NF Service Consumer (e.g. the initial AMF) shall relocate the UE Context in the target AMF by invoking the "relocate" custom method on the URI of an "Individual ueContext" resource (see clause 6.1.3.2.4). See also Figure 5.2.2.2.5.1-1.

Figure 5.2.2.2.5.1-1 Relocate UE Context

1. The NF Service Consumer, e.g. initial AMF, shall send a POST request to relocate the UE context in the target AMF. The payload body of the POST request shall contain a UeContextRelocateData structure.

The UE context shall contain trace control and configuration parameters, if signalling based trace has been activated (see 3GPP TS 32.422 [30]).

For an EPS to 5GS handover procedure, the NF Service Consumer shall carry per PDU session the S-NSSAI for serving PLMN, the MME Control Plane Address and the TEID in the request. If S-NSSAI for interworking is configured and used in initial AMF for the PDU session, the initial AMF shall also carry the configured S-NSSAI for interworking to the target AMF, as specified in clause 4.11.1.2.2 of 3GPP TS 23.502 [3]. In Home Routed roaming case, the S-NSSAI for serving PLMN is derived by the initial AMF based on the S-NSSAI for home PLMN retrieved from SMF+PGW-C, as specified in 3GPP TS 23.502 [3].

2a. On success, the target AMF shall respond with the status code "201 Created" if the request is accepted, together with a HTTP Location header to provide the location of the newly created resource. The payload body of the POST response shall contain the representation of the created UE Context.

2b. On failure to relocate the UE context or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.6.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.3.2.4.6.2-2.

If the target RAN rejects the Handover Request, the target AMF shall send Forward Relocation Response message directly to the source MME over the N26 interface, carrying the appropriate cause value.

5.2.2.2.6 CancelRelocateUEContext

5.2.2.2.6.1 General

The CancelRelocateUEContext service operation is used during the following procedure:

– EPS to 5GS Handover with AMF re-allocation, Handover Cancel procedure (see 3GPP TS 23.502 [3], clause 4.11.1.2.3)

The CancelRelocateUEContext service operation is invoked by a NF Service Consumer (i.e. initial AMF), towards the AMF (acting as target AMF), when the initial AMF receives Forward Cancel Request from the source MME during EPS to 5GS Handover with AMF re-allocation porceudre, to trigger the target AMF to release the UE Context.

The NF Service Consumer (i.e. the initial AMF) shall cancel the UE Context Relocation by using the HTTP "cancel-relocate" custom operation with the URI of the "Individual UeContext" resource (See clause 6.1.3.2.4.2). See also Figure 5.2.2.2.6.1-1.

Figure 5.2.2.2.6.1-1 Cancel Relocate UE Context

1. The NF Service Consumer, i.e. initial AMF, shall send a POST request, to release the ueContext in the target AMF. The payload body of the POST request shall contain the UeContextCancelRelocateData that needs to be passed to the target AMF.

2a. On success, the target AMF shall return "204 No Content" with an empty payload body in the POST response.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.7.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.2.4.7.2-2.

5.2.2.3 UE Specific N1N2 Message Operations

5.2.2.3.1 N1N2MessageTransfer

5.2.2.3.1.1 General

The N1N2MessageTransfer service operation is used by a NF Service Consumer to transfer N1 and/or N2 information to the UE and/or 5G-AN through the AMF in the following procedures:

– Network triggered Service Request (see clause 4.2.3.3 of 3GPP TS 23.502 [3])

– PDU Session establishment (see clause 4.3.2 of 3GPP TS 23.502 [3])

– PDU Session modification (see clause 4.3.3 of 3GPP TS 23.502 [3])

– PDU Session release (see clause 4.3.4 of TS 3GPP 23.502 [3])

– Session continuity, service continuity and UP path management (see clause 4.3.5 of 3GPP TS 23.502 [3])

– Inter NG-RAN node N2 based handover (see clause 4.9.1.3 of 3GPP TS 23.502 [3])

– SMS over NAS procedures (see clause 4.13.3 of 3GPP TS 23.502 [3]

– UE assisted and UE based positioning procedure (see clause 6.11.1 of 3GPP TS 23.273 [42])

– Network assisted positioning procedure (see clause 6.11.2 of 3GPP TS 23.273 [42])

– LCS Event Report, Event Reporting in RRC INACTIVE state procedures, LCS Cancel Location and LCS Periodic-Triggered Invoke procedures (see clause 6.3 and clause 6.7 of 3GPP TS 23.273 [42])

– UE configuration update procedure for transparent UE policy delivery (see clause 4.2.4.3 of 3GPP TS 23.502 [3])

– UPF anchored Mobile Terminated Data Transport in Control Plane CIoT 5GS Optimisation (see clause 4.24.2 of 3GPP TS 23.502 [3])

– NEF Anchored Mobile Terminated Data Transport (see clause 4.25.5 of 3GPP TS 23.502 [3])

– System interworking procedures with EPC (see clause 4.3 in 3GPP TS 23.501 [2] and clause 4.11 in 3GPP TS 23.502 [3])

– SMF triggered N3 data transfer establishment procedure (see clause 4.2.10.2 of 3GPP TS 23.502 [3])

– 5G-RG requested PDU Session Establishment via W-5GAN (see clause 7.3.1 of 3GPP TS 23.316 [48])

– 5G-RG or Network requested PDU Session Modification via W-5GAN (see clause 7.3.2 of 3GPP TS 23.316 [48])

– 5G-RG or Network requested PDU Session Release via W-5GAN (see clause 7.3.3 of 3GPP TS 23.316 [48])

– FN-RG related PDU Session Establishment via W-5GAN (see clause 7.3.4 of 3GPP TS 23.316 [48])

– CN-initiated selective deactivation of UP connection of an existing PDU Session associated with W-5GAN Access (see clause 7.3.5 of 3GPP TS 23.316 [48])

– FN-RG or Network Requested PDU Session Modification via W-5GAN (see clause 7.3.6 of 3GPP TS 23.316 [48])

– FN-RG or Network Requested PDU Session Release via W-5GAN (see clause 7.3.7 of 3GPP TS 23.316 [48])

– Non-5G capable device behind 5G-CRG and FN-CRG requested PDU Session Establishment via W-5GAN (see clause 4.10a of 3GPP TS 23.316 [48])

– Non-5G capable device behind 5G-CRG and FN-CRG or Network Requested PDU Session Modification via W-5GAN (see clause 4.10a of 3GPP TS 23.316 [48])

– Non-5G capable device behind 5G-CRG and FN-CRG or Network Requested PDU Session Release via W-5GAN (see clause 4.10a of 3GPP TS 23.316 [48])

– Handover procedures between 3GPP access / 5GC and W-5GAN access (see clause 7.6.3 of 3GPP TS 23.316 [48])

– Handover from 3GPP access / EPS to W-5GAN / 5GC (see clause 7.6.4.1 of 3GPP TS 23.316 [48])

– Transfer UAV specific data via N1 SM (see clause 5.2.4.3 of 3GPP TS 23.256 [56])

– MBS join and Session establishment procedure (see clause 7.2.1.3 of 3GPP TS 23.247 [55])

– MBS activation procedure (see clause 7.2.5.2 of 3GPP TS 23.247 [55])

– Multicast session leave requested by the network or MBS session release (see clause 7.2.2.3 of 3GPP TS 23.247 [55])

NOTE: Though in 3GPP TS 23.502 [3] the procedure is called "UE configuration update procedure for transparent UE policy delivery", as per 3GPP TS 24.501 [11] clause 5.4.5.3.1, the network initiated NAS transport procedure is used.

The NF Service Consumer shall invoke the service operation by using HTTP method POST, to request the AMF to transfer N1 and/or N2 information for a UE and/or 5G-AN, with the URI of "N1 N2 Messages Collection" resource (see clause 6.1.3.5.3.1).

The NF Service Consumer may include the following information in the HTTP Request message body:

– SUPI

– PDU Session ID or LCS Correlation ID depending on the N1/N2 message class to be transferred

– N2 SM Information (PDU Session ID, QoS profile, CN N3 Tunnel Info, S-NSSAI)

– N1 Message Container, including a N1 SM, LPP message, LCS message, SMS, UPDP message

– N2 Information Container, including N2 SM, NRPPa message, PWS or RAN related information

– Mobile Terminated Data (i.e. CIoT user data container)

– Allocation and Retention Priority (ARP)

– Paging Policy Indication

– 5QI

– Notification URL (used for receiving Paging Failure Indication)

– Last Message Indication

– NF Instance Identifier and optionally Service Instance Identifier of the NF Service Consumer (e.g. an LMF or SMF)

– N1 SM Skipping Indication

– Area of Validity for N2 SM Information

– A MA PDU Session Accepted indication, if a MA-PDU session is established;

– Extended Buffering Support Indication, if SMF determines that Extended Buffering applies during Network triggered Service Request Procedure (see clause 4.2.3.3 of 3GPP TS 23.502 [3]), UPF anchored Mobile Terminated Data Transport in Control Plane CIoT 5GS Optimisation procedure (see clause 4.24.2 of 3GPP TS 23.502 [3]) or NEF Anchored Mobile Terminated Data Transport (see clause 4.25.5 of 3GPP TS 23.502 [3]);

– Target Access type towards which the SMF requests to send N2 information and optionally N1 information, for a Multi-Access (MA) PDU session, or through which the LMF requests to transfer an LPP message to the UE.

During an intra-AMF handover between 3GPP and non-3GPP accesses, the SMF shall include the targetAccess IE set to the old access type in the HTTP Request message body, when releasing the N2 PDU session resources in the old access (see step 3 of Figure 4.9.2.1-1 and step 3 of Figure 4.9.2.2-1 of 3GPP TS 23.502 [3]).

Figure 5.2.2.3.1.1-1 N1N2MessageTransfer for UE related signalling

1. The NF Service Consumer shall send a POST request to transfer N1 and N2 information. The NF Service Consumer may include a N1N2MessageTransfer Notification URI to AMF in the request message.

2a. On success, i.e. if the request is accepted and the AMF is able to transfer the N1/N2 message to the UE and/or the AN, the AMF shall respond with a "200 OK" status code. The AMF shall set the cause IE in the N1N2MessageTransferRspData as "N1_N2_TRANSFER_INITIATED" in this case.

The AMF shall respond with a "200 OK" status code and set the cause IE in the N1N2MessageTransferRspData to "N2_MSG_NOT_TRANSFERRED", if the N1N2MessageTransfer request included an area of validity for the N2 SM Information, the UE is in CM-CONNECTED state and outside of the area of validity.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.5.3.1-3 shall be returned. For a 4xx/5xx response, the message body shall contain a N1N2MessageTransferError structure, including:

– a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.5.3.1-3;

5.2.2.3.1.2 Detailed behaviour of the AMF

When an NF service consumer is requesting to send N1 and/or N2 information and the UE is in CM-IDLE state for the access type for which the N1 and/or N2 information is related (called "associated access type" hereafter in this clause), the requirements specified in clause 5.2.2.3.1.1 shall apply with the following modifications:

NOTE: N1 and/or N2 Session Management information is related to the access type of the targeted PDU session for a single access PDU session, or to the Target Access received in the request for a MA PDU session; LCS related N2 (NRPPa) information is related to 3GPP access in this release of specification.

4xx and 5xx response cases shall also apply to UEs in CM-CONNECTED state, when applicable.

2xx Response Cases:

Case A: When UE is CM-IDLE in 3GPP access and the associated access type is 3GPP access:

a) Same as step 2a of Figure 5.2.2.3.1.1-1, the AMF should respond with the status code "200 OK", if "skipInd" attribute is set to "true" in the request body, with a response body that carries the cause "N1_MSG_NOT_TRANSFERRED".

b) Same as step 2a of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "202 Accepted", if the asynchronous type communication is invoked and hence the UE is not paged, update the UE context and store N1 and/or N2 information and initiate communication with the UE and/or 5G-AN when the UE becomes reachable. In this case the AMF shall provide the URI of the resource in the AMF in the "Location" header of the response, which contains information regarding the stored N1/N2 message. The AMF shall also provide a response body containing the cause, "WAITING_FOR_ASYNCHRONOUS_TRANSFER" that represents the current status of the N1/N2 message transfer;

c) Same as step 2a of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "202 Accepted", if paging is issued when the UE is in CM-IDLE and reachable for 3GPP access, with a response body that carries a cause "ATTEMPTING_TO_REACH_UE" as specified in clause 4.2.3.3 and 5.2.2.2.7 of 3GPP TS 23.502 [3].

Case B: When UE is CM-IDLE in Non-3GPP access but CM-CONNECTED in 3GPP access and the associated access type is Non-3GPP access:

a) Same as step 2a of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "200 OK" with cause "N1_N2_TRANSFER_INITIATED" and initiate N1 NAS SM message transfer via 3GPP access, if the NF service consumer (i.e. SMF) requests to send only N1 NAS SM message without any associated N2 SM information, and the current access type related to the PDU session is Non-3GPP access and the UE is CM-CONNECTED in 3GPP access.

b) Same as step 2a of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "202 Accepted", if NAS Notification procedure is issued when the UE is in CM-CONNECTED in 3GPP access, with a response body that carries a cause "ATTEMPTING_TO_REACH_UE" as specified in step 4c of clause 4.2.3.3 and 5.2.2.2.7 of 3GPP TS 23.502 [3].

Case C: When UE is CM-IDLE in both Non-3GPP access and 3GPP access and the associated access type is Non-3GPP access:

All the bullets specified in Case A are applicable.

The NF Service Consumer shall not send any further signalling for the UE if it receives a POST response body with a cause "ATTEMPTING_TO_REACH_UE" unless it has higher priority signalling. In such a case the response shall include the "Location" header containing the URI of the resource created in the AMF, which holds the status of the N1/N2 message transfer, e.g. "…/n1-n2-messages/{n1N2MessageId}". The AMF shall:

– store the N1 and/or N2 information related to 3GPP access and, when the UE responds with a Service Request, shall initiate communication with the UE and/or 5G-AN using the stored N1 and/or N2 information;

– store the N1 NAS SM information related to Non-3GPP access if no N2 information was received and the AMF initiated paging towards the UE. Later when the UE responds with a Service Request,the AMF shall initiate communication with the UE using the stored N1 information via 3GPP access;

– inform the SMF which invoked the service operation, that the access type of the PDU Session can be changed from Non-3GPP access to 3GPP access as specified in clause 5.2.2.3.2.1 of 3GPP TS 29.502 [16], when the UE responds with a "List Of Allowed PDU Sessions" and the indicated non-3GPP PDU session of the N2 (and N1 if received) information is included in the list; or

– notify the NF which invoked the service operation, as specified in clause 5.2.2.3.2, if the Notification URI is provided, when the AMF determines that the paging or NAS Notification has failed or when the UE responds with a "List Of Allowed PDU Sessions" and the indicated Non-3GPP PDU session of the N2 (and N1 if received) information is not included in the list.

4xx Response Cases:

– Same as step 2b of Figure 5.2.2.3.1.1-1, the AMF shall respond with status code "409 Conflict" in the following cases:

– if the UE is in 3GPP access and there is already an ongoing paging procedure with higher or same priority, the AMF shall set the application error as "HIGHER_PRIORITY_REQUEST_ONGOING" in the "cause" attribute of the ProblemDetails structure of the POST response body. The AMF may provide a retry timer value to the NF Service Consumer in order for the NF Service Consumer to retry the request after the expiry of the timer. When the retry timer is provided, the NF Service Consumer shall not initiate the downlink messaging until the timer expires. The AMF may also provide the ARP value of the QoS flow that has triggered the currently ongoing highest priority paging, so that the NF Service Consumer (e.g. SMF) knows that if any subsequent trigger initiating downlink messaging for a QoS flow with the same or lower priority happens.

– if there is an ongoing registration procedure (see clause 4.2.3.3 of 3GPP TS 23.502 [3]) the AMF shall set the application error as "TEMPORARY_REJECT_REGISTRATION_ONGOING" in the "cause" attribute of the ProblemDetails structure in the POST response body; The AMF may provide a retry timer value to the NF Service Consumer in order for the NF Service Consumer to retry the request after a short period. When the retry timer is provided, the NF Service Consumer should not initiate new N1/N2 Message Transfer request until the timer expires.

– if this is a request to transfer a N2 PDU Session Resource Modify Request or a N2 PDU Session Resource Release Command to a 5G-AN and if the UE is in CM-IDLE state at the AMF for the Access Network Type associated to the PDU session (see clauses 4.3.3 and 4.3.4 of 3GPP TS 23.502 [3] and clause 5.3.2.1 of 3GPP TS 23.527 [33]), the AMF shall set the application error "UE_IN_CM_IDLE_STATE" in the "cause" attribute of the ProblemDetails structure in the POST response body.

– if there is an ongoing Xn or N2 handover procedure (see clause 4.9.1.2.1 and 4.9.1.3.1 of 3GPP TS 23.502 [3]) the AMF shall set the application error as "TEMPORARY_REJECT_HANDOVER_ONGOING" in the "cause" attribute of the ProblemDetails structure in the POST response body, if the AMF rejects the request due to the on-going handover.

– if the RAT Type is NB-IoT, and the UE already has 2 PDU Sessions with active user plane resources, the AMF shall set the application error as "MAX_ACTIVE_SESSIONS_EXCEEDED" in POST response body.

– if Paging Restrictions information restricts the N1N2MessageTransfer request from causing paging (see clause 4.2.3.3 of 3GPP TS 23.502 [3]) the AMF shall set the application error as "REJECTION_DUE_TO_PAGING_RESTRICTION" in the "cause" attribute of the ProblemDetails structure in the POST response body.

– Same as step 2b of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "403 Forbidden", if the UE is in a Non-Allowed Area and the service request is not for regulatory prioritized service. The AMF shall set the application error as "UE_IN_NON_ALLOWED_AREA" in POST response body.

– The NF service consumer (i.e. the SMF) that receives this application error may supress subsequent message (e.g. N1N2MessageTransfer) to the AMF for non regulatory prioritized service. In this case, the NF service consumer (i.e. the SMF) should subscribe the Reachability-Report event for "UE Reachability Status Change" from the AMF, so as to get notified by the AMF when the UE becomes reachable again.

– Same as step 2b of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "403 Forbidden ", if the NF service consumer (e.g. an LMF) is requesting to send N1 LPP message to the UE and the UE has indicated that it does not support LPP in N1 mode during registration procedure (see clause 5.5.1.2.2 and 5.5.1.3.2 of 3GPP TS 24.501 [11]). The AMF shall set the application error to "UE_WITHOUT_N1_LPP_SUPPORT" in POST response body.

– Same as step 2b of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "403 Forbidden", if the request body includes an nfId IE indicating an SMF instance which is different from the stored SMF instance hosting the SM Context of the PDU session. The AMF shall set the application error to "INVALID_SM_CONTEXT" in POST response body. During procedures with SM Context relocation, e.g. UE mobility procedures with I-SMF insertion/change/removal, the AMF shall allow N1N2MessageTransfer from both SMF instances holding the old and new SM Contexts.

The NF service consumer (i.e. the SMF) that receives this application error shall remove the SM Context for the PDU session and release the PDU session resource in (H-)SMF if available. The SMF shall not send a SMContextStatusNotification to the AMF for the PDU session release.

5xx Response Cases:

– Same as step 2b of Figure 5.2.2.3.1.1-1, the AMF shall respond with the status code "504 Gateway Timeout", if the UE is currently unreachable (e.g., due to the UE in MICO mode, the UE using extended idle mode DRX or the UE is only registered over Non-3GPP access and its state is CM-IDLE). The AMF shall set the application error as "UE_NOT_REACHABLE" in POST response body. If Extended Buffering Support Indication is received in the request, the AMF shall include the Estimated Maximum Waiting time in the response body when the message is rejected due to the UE in MICO mode or the UE using extended idle mode DRX.

– step 2b of Figure 5.2.2.3.1.1-1, the AMF may respond with the status code "504 Gateway Timeout", if the UE is temporarily not responding (e.g., not responding to the paging). The AMF shall set the application error as "UE_NOT_RESPONDING" in POST response body. The AMF may provide a retryAfter timer value to the NF Service Consumer in order for the NF Service Consumer to throttle sending further N1/N2 Message Transfer request for a short period. When the retry timer is provided, the NF Service Consumer should not initiate new N1/N2 Message Transfer request until the timer expires.

5.2.2.3.2 N1N2Transfer Failure Notification

The AMF uses this notification to inform the NF service consumer that initiated an earlier

Namf_Communication_N1N2MessageTransfer, that the AMF failed to deliver the N1 and/or N2 message. The HTTP POST method shall be used on the notification callback URI provided by the NF service consumer as specified in clause 5.2.2.3.1.2.

Figure 5.2.2.3.2-1 N1N2Transfer Failure Notification for UE related signalling

1. If the NF service consumer had provided a notification URI (see clause 5.2.2.3.1.2), the AMF shall send a POST request to the NF Service Consumer on that Notification URI when the AMF determines that:

– the paging or NAS Notification has failed;

– the indicated non-3GPP PDU session is not allowed to move to 3GPP access;

– the UE has rejected the page as defined in 3GPP TS 23.501 [2] clause 5.38.4;

– the delivery of the N1 message fails, e.g. in case the UE is in RRC Inactive and NG-RAN paging was not successful or in case an Xn or N2 handover is being triggered at the NG-RAN

The AMF shall include the N1N2MessageTransfer request resource URI returned earlier in the N1N2MessageTransfer response if any (see clause 5.2.2.3.1.2), otherwise a dummy URI (see clause 6.1.6.2.30), in the POST request body. The AMF shall also include a N1/N2 message transfer cause information in the POST request body and set the value as specified in clause 6.1.5.6.3.1.

The NF Service Consumer shall delete any stored representation of the N1N2MessageTransfer request resource URI upon receiving this notification.

The AMF may also include a "retryAfter" IE in the POST request body in order for the NF consumer to throttle sending further N1/N2 Message Transfer request for a short period, e.g. to reduce unnecessary paging to an unresponding UE for a period of time to save the RAN resources.

2. The NF Service Consumer shall send a response with "204 No Content" status code.

On failure or redirection, one of the HTTP status codes together with the response body listed Table 6.1.5.6.3.1-2 shall be returned.

5.2.2.3.3 N1N2MessageSubscribe

5.2.2.3.3.1 General

The N1N2MessageSubscribe service operation is used by a NF Service Consumer (e.g. PCF) to subscribe to the AMF for notifying N1 messages of a specific type (e.g. UPDP) or N2 information of a specific type. For the N1 message class UPDP, a PCF shall subscribe for the N1 message notification with the AMF to receive the N1 messages from UE that are related to UE Policy.

NOTE: Step 0 of clause 4.2.4.3 of 3GPP TS 23.502 [3] specifies that the PCF can split the UPDP transfer towards UE into multiple units. One UE specific callback URI is registered with the AMF by the PCF for the AMF to notify all UPDP message responses from the UE to the same callback URI. As a result, an explicit subscription per UE policy association is defined in stage 3 for this purpose.

An NF Service Consumer (e.g. PCF) may subscribe to notifications of specific N1 message type (e.g. LPP or UPDP) or N2 information type. In this case the NF Service Consumer shall subscribe by using the HTTP POST method with the URI of the "N1N2 Subscriptions Collection for Individual UE Contexts" resource (See clause 6.1.3.3). See also Figure 5.2.2.3.3.1-1.

Figure 5.2.2.3.3.1-1 N1N2 Message Subscribe

1. The NF Service Consumer shall send a POST request to create a subscription resource in the AMF for a UE specific N1/N2 message notification. The payload body of the POST request shall contain:

– N1 and/or N2 Message Type, identifying the type of N1 and/or N2 message to be notified

– A callback URI for the notification

2. If the request is accepted, the AMF shall include a HTTP Location header to provide the location of a newly created resource (subscription) together with the status code 201 indicating the requested resource is created in the response message.

On failure or redirection, one of the HTTP status codes together with the response body listed Table 6.1.3.3.3.1-3 shall be returned.

5.2.2.3.4 N1N2MessageUnSubscribe

5.2.2.3.4.1 General

The N1N2MessageUnSubscribe service operation is used by a NF Service Consumer (e.g. PCF) to unsubscribe to the AMF to stop notifying N1 messages of a specific type (e.g. LPP or UPDP).

The NF Service Consumer shall use the HTTP method DELETE with the URI of the "N1N2 Individual Subscription" resource (See clause 6.1.3.7.3.1), to request the deletion of the subscription for the N1 / N2 message towards the AMF. See also Figure 5.2.2.3.4.1-1.

Figure 5.2.2.3.4.1-1 N1N2 Message UnSubscribe

1. The NF Service Consumer shall send a DELETE request to delete an existing subscription resource in the AMF.

2. If the request is accepted, the AMF shall reply with the status code 204 indicating the resource identified by subscription ID is successfully deleted, in the response message.

On failure or redirection, one of the HTTP status codes together with the response body listed Table 6.1.3.4.3.1-3 shall be returned.

5.2.2.3.5 N1MessageNotify

5.2.2.3.5.1 General

The N1MessageNotify service operation is used by an AMF notifying the N1 message received from the UE to a destination CN NF, and it is used in the following procedures:

– Registration with AMF re-allocation (see clause 4.2.2.2.3 of 3GPP TS 23.502 [3])

– UE assisted and UE based positioning procedure (see clause 6.11.1 of 3GPP TS 23.273 [42])

– LCS Event Report, Event Reporting in RRC INACTIVE state procedures, LCS Cancel Location and LCS Periodic-Triggered Invoke procedures (see clause 6.3 and clause 6.7 of 3GPP TS 23.273 [42])

– UE configuration update procedure for transparent UE policy delivery (See clause 4.2.4.3 in 3GPP TS 23.502 [3])

– UE triggered policy provisioning procedure to request UE policies. (See clause 6.2.4 in 3GPP TS 23.287 [47] and clause 6.2.4 in 3GPP TS 23.304 [51])

NOTE: Though in 3GPP TS 23.502 [3] the procedure is called "UE configuration update procedure for transparent UE policy delivery", as per 3GPP TS 24.501 [11] clause 5.4.5.2.1, the UE initiated NAS transport procedure is used.

The AMF shall use HTTP POST method to the N1 Notification URI provided by the NF Service Consumer via N1N2MessageSubscribe service operation (See clause 5.2.2.3.3). See also figure 5.2.2.3.5.1-1.

Figure 5.2.2.3.5.1-1 N1 Message Notify

1. The AMF shall send a HTTP POST request to the N1 Notification URI, and the payload body of the POST request shall contain an N1MessageNotificatoin data structure with the subscribed N1 message.

2a. On success, "204 No Content" shall be returned and the payload body of the POST response shall be empty.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.5.4.3.1-3 shall be returned. The message body shall contain a ProblemDetails object with "cause" set to one of the corresponding application errors listed in Table 6.1.5.4.3.1-3.

5.2.2.3.5.2 Using N1MessageNotify in the Registration with AMF Re-allocation Procedure

In the Registration with AMF re-allocation procedure, the N1MessageNotify service operation is invoked by a NF Service Producer, i.e. an Initial AMF, towards a NF Service Consumer, e.g. the target AMF, which is selected to serve the UE, by the initial AMF.

The requirements specified in clause 5.2.2.3.5.1 shall apply with the following modifications:

1. The initial AMF discovers the NF Service Consumer (e.g. the target AMF) from the NRF, and fetch N1 Notification URI from the default notification subscription registered with "N1_MESSAGE" notification type and "5GMM" N1 message class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29].

NOTE: The alternate AMF is expected to have registered a callback URI with the NRF.

2. Same as step 1 of Figure 5.2.2.3.5.1-1, the request payload shall include the following information in the HTTP POST Request message body:

– RAN NGAP ID and initial AMF name (the information enabling (R)AN to identify the N2 terminating point);

– RAN identity, e.g. RAN Node Id, RAN N2 IPv4/v6 address;

– Information from RAN, e.g. User Location, RRC Establishment Cause and UE Context Request;

– the N1 message, which shall be the complete Registration Request message in clear text if the UE has a valid NAS security context, or as the one contained in the NAS message container IE in the Security Mode Complete message as specified in clause 4.2.2.2.3 of 3GPP TS 23.502 [2];

– the UE’s SUPI and MM Context;

– the Allowed NSSAI together with the corresponding NSI IDs (if network slicing is used and the initial AMF has obtained).

5.2.2.3.5.3 Using N1MessageNotify in the UE Assisted and UE Based Positioning Procedure

In the UE assisted and UE based positioning procedure, the N1MessageNotify service operation is invoked by the AMF, towards the LMF, to notify the N1 UE positioning messages received from the UE.

The requirements specified in clause 5.2.2.3.5.1 shall apply with the following modifications:

1. If the corresponding N1 notification URI is not available, the AMF shall retrieve the NF profile of the NF Service Consumer (e.g. the LMF) from the NRF using the NF Instance Identifier received during corresponding N1N2MessageTransfer service operation (see clause 5.2.2.3.1), and further identify the corresponding service instance if Service Instance Identifier was also received, and fetch N1 Notification URI from the default notification subscription registered with "N1_MESSAGE" notification type and "LPP" N1 message class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29]).

2. Same as step 1 of Figure 5.2.2.3.5.1-1, the request payload shall include the following information:

– the N1 Uplink Positioning Message;

– LCS correlation identifier.

5.2.2.3.5.4 Using N1MessageNotify in the UE Configuration Update for transparent UE Policy delivery

In the UE Configuration Update for transparent UE Policy delivery procedure, the N1MessageNotify service operation is invoked by the AMF, towards the PCF which subscribed to be notified with UPDP messages received from the UE.

The requirements specified in clause 5.2.2.3.5.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.3.5.1-1. The request payload shall include the following information:

– the UPDP message.

5.2.2.3.5.5 Using N1MessageNotify in the LCS Event Report, Event Reporting in RRC INACTIVE state procedures, LCS Cancel Location and LCS Periodic-Triggered Invoke Procedures

In the LCS Event Report, Event Reporting in RRC INACTIVE state procedures, LCS Cancel Location and LCS Periodic-Triggered Invoke procedure, the N1MessageNotify service operation is invoked by the AMF, towards the LMF, to notify the N1 UE LCS messages received from the UE.

The requirements specified in clause 5.2.2.3.5.1 shall apply with the following modifications:

1. If the corresponding N1 notification URI is not available, the AMF shall retrieve the NF profile of the NF Service Consumer (e.g. the LMF) from the NRF using the NF Instance Identifier received during corresponding N1N2MessageTransfer service operation (see clause 5.2.2.3.1), and further identify the corresponding service instance if Service Instance Identifier was also received, and fetch N1 Notification URI from the default notification subscription registered with "N1_MESSAGE" notification type and "LCS" N1 message class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29]).

2. Same as step 1 of Figure 5.2.2.3.5.1-1, the request payload shall include the following information:

– the N1 Uplink LCS Message;

– LCS correlation identifier;

– indication of Control Plane CIoT 5GS Optimisation if Control Plane CIoT 5GS Optimisation is being used.

and may include serving cell ID if it is available;

NOTE: For the EventReport message and UE initiated CancelDeferredLocation message, the AMF includes the deferred routing identifier received from UE in N1 UL NAS TRANSPORT message as LCS correlation identifier. The LCS correlation identifier can assist a serving LMF in identifying the periodic or triggered location session if the same LMF had assigned the deferred routing identifier or can indicate to the LMF that it is acting as a default LMF.

5.2.2.3.5.6 Using N1MessageNotify in the UE triggered policy provisioning procedure to request UE policies

In the UE triggered policy provisioning procedure, the N1MessageNotify service operation is invoked by the AMF, towards the PCF which subscribed to be notified with UPDP messages received from the UE.

The requirements specified in clause 5.2.2.3.5.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.3.5.1-1. The request payload shall include the following information:

– the UPDP message.

5.2.2.3.6 N2InfoNotify

5.2.2.3.6.1 General

The N2InfoNotify service operation is used during the following procedure:

– Inter NG-RAN node N2 based handover procedure (see 3GPP TS 23.502 [3], clauses 4.9.1.3.3, 4.9.1.3.3a and 4.23.7.3);

– Network assisted positioning procedure (see clause 6.11.2 of 3GPP TS 23.273 [42])

– AMF planned removal procedure with UDSF deployed (see clause 5.21.2.2.1 of 3GPP TS 23.501 [2]), to forward uplink N2 signalling to a different AMF.

The N2InfoNotify service operation is invoked by AMF, to notify a NF Service Consumer that subscribed N2 information has been received from access network.

The AMF shall use HTTP POST method to the N2Info Notification URI provided by the NF Service Consumer via N1N2MessageSubscribe service operation (See clause 5.2.2.3.3). See also figure 5.2.2.3.6.1-1.

Figure 5.2.2.3.6.1-1 N2 Information Notify

1. The AMF shall send a HTTP POST request to the n2NotifyCallbackUri, and the payload body of the POST request shall contain a N2InformationNotification data structure, containing the N2 information that was subscribed by the NF Service Consumer.

2a. On success, "204 No Content" shall be returned and the payload body of the POST response shall be empty.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.5.5.3.1-3 shall be returned. The message body shall contain a ProblemDetails object with "cause" set to one of the corresponding application errors listed in Table 6.1.5.5.3.1-3.

5.2.2.3.6.2 Using N2InfoNotify during Inter NG-RAN node N2 based handover procedure

The N2InfoNotify service operation is invoked by a NF Service Producer, e.g. the target AMF, towards the NF Service Consumer, i.e. the source AMF, to notify that the handover procedure has been successful in the target side, for a given UE.

Figure 5.2.2.3.6.2-1 N2 Information Notify during N2 Handover execution

The requirements specified in clause 5.2.2.3.6.1 shall apply with the following modifications:

0. During an inter AMF handover procedure, the source AMF, acting as a NF Service Consumer, when invoking the CreateUEContext service operation (see clause 5.2.2.2.3), shall include a N2Info Notification URI to the target AMF in the HTTP request message.

1. Same as step 1 of Figure 5.2.2.3.6.1-1, the request payload shall contain the following information:

– notification payload (see clause 6.1.5.5) without the "n2InfoContainer" attribute;

– the "notifyReason" attribute set to "HANDOVER_COMPLETED";

– the "smfChangeInfoList" attribute including the UE’s PDU Session ID(s) for which the I-SMF or V-SMF has been changed or removed, if any, with for each such PDU session, the related "smfChangeIndication" attribute set to "CHANGED" or "REMOVED", if the I-SMF or the V-SMF is changed or removed respectively.

– the "notifySourceNgRan" attribute set to "true" during an Inter NG-RAN node N2 based DAPS handover procedure, if the target AMF receives this indication in the Handover Notify from the target NG-RAN node (see clause 4.9.1.3.3a of 3GPP TS 23.502 [3]).

2. Same as Step 2a of Figure 5.2.2.3.6.1-1, with the following additions/modifications:

– the source AMF shall release the PDU Session(s) listed in the toReleaseSessionList attribute in the payload;

– if the smfChangeInfoList attribute was received in the request, the source AMF shall release the SM Context at the I-SMF or V-SMF only, for all the PDU sessions listed in the smfChangeInfoList attribute with the smfChangeIndication attribute set to "CHANGED" or "REMOVED";

– the source AMF shall remove the individual ueContext resource. The source AMF may choose to start a timer to supervise the release of the UE context resource and may keep the individual ueContext resource until the timer expires;

– if Secondary RAT usage data have been received from the source NG-RAN and buffered at the source AMF for one or more PDU sessions as specified in step 2a0 of clause 4.9.1.3.3 of 3GPP TS 23.502 [3], the source AMF shall send a 200 OK response with the Secondary RAT usage data included in the response payload for one or more PDU sessions.

– if the "notifySourceNgRan" attribute was set to "true" in the request, the source AMF shall send a HANDOVER SUCCESS to the source NG-RAN (see clause 4.9.1.3.3a of 3GPP TS 23.502 [3]).

NOTE: This notification is due to an implicit subscription and hence no explicit subscription Id is created. UE context Id is included as the notification subscription Id for the NF Service Consumer (e.g. Source AMF) to co-relate the notification to an earlier initiated UE context creation during a handover procedure.

5.2.2.3.6.3 Using N2InfoNotify during Location Services procedures

The N2InfoNotify service operation is invoked by a NF Service Producer, i.e. the AMF, towards the NF Service Consumer, e.g. the LMF, to notify the positioning parameters received from the 5G-AN in the NRPPa message.

The requirements specified in clause 5.2.2.3.6.1 shall apply with the following modifications:

1. If the corresponding N2 notification URI is not available, the AMF shall retrieve the NF profile of the NF Service Consumer (e.g. the LMF) from the NRF using the NF Instance Identifier received during corresponding N1N2MessageTransfer service operation (see clause 5.2.2.3.1), and further identify the corresponding service instance if Service Instance Identifier was also received, and fetch N2 Notification URI from the default subscription registered with "N2_INFORMATION" notification type and "NRPPa" N2 information class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29]).

2. Same as step 1 of Figure 5.2.2.3.6.1-1, the request payload shall contain N2 information of type NRPPa and LCS correlation identifier.

5.2.2.3.6.4 Using N2InfoNotify during AMF planned removal procedure with UDSF deployed procedure

In the AMF planned removal procedure with UDSF deployed (see clause 5.21.2.2.1 of 3GPP TS 23.501 [2]), the N2InfoNotify service operation is invoked by a NF Service Producer, i.e. an initial AMF, towards the NF Service Consumer, i.e. the target AMF, to forward uplink N2 signalling to the target AMF.

The requirements specified in clause 5.2.2.3.6.1 shall apply with the following modifications:

1. If the N2 notification URI is not available, the initial AMF shall discover the NF Service Consumer (i.e. the target AMF) from the NRF, and fetch the N2 Notification URI from the default notification subscription registered with "N2_INFORMATION" notification type and "RAN" N2 message class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29].

NOTE: The target AMF is expected to have registered a callback URI with the NRF.

2. Same as step 1 of Figure 5.2.2.3.6.1-1, the request payload shall contain the following information in the HTTP POST Request message body:

– N2 information of type "RAN";

– N2 message;

– initial AMF name;

– RAN identity, e.g. RAN Node Id, RAN N2 IPv4/v6 address.

5.2.2.4 Non-UE N2 Message Operations

5.2.2.4.1 NonUeN2MessageTransfer

5.2.2.4.1.1 General

The NonUeN2MessageTransfer service operation is used by a NF Service Consumer to transfer N2 information to the 5G-AN through the AMF in the following procedures:

– Obtaining non-UE associated network assistance data (See clause 4.13.5.6 in 3GPP TS 23.502 [3]);

– Warning Request Transfer procedures (See clause 9A in 3GPP TS 23.041 [20]);

– Configuration Transfer procedure (see clause 5.26 of 3GPP TS 23.501 [2])

– RIM Information Transfer procedures (see clause 8.16 of 3GPP TS 38.413 [12]).

– Broadcast of Assistance Data by an LMF (see clause 6.14.1 of 3GPP TS 23.273 [42]).

The NF Service Consumer shall invoke the service operation by sending POST to the URI of the "transfer" customer operation on the "Non UE N2Messages Collection" resource (See clause 6.1.3.8.4.2) on the AMF. See also figure 5.2.2.4.1.1-1.

Figure 5.2.2.4.1.1-1 Non-UE N2 Message Transfer

1. The NF Service Consumer shall invoke the custom operation for non UE associated N2 message transfer by sending a HTTP POST request, and the request body shall carry the N2 information to be transferred.

2a. On success, AMF shall respond a "200 OK" status code with N2InformationTransferRspData data structure.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.8.4.2.2-2shall be returned with the message body containing a N2InformationTransferError structure, including a ProblemDetails attribute with the "cause" attribute set to one of the application errors listed in Table 6.1.3.8.4.2.2-2.

5.2.2.4.1.2 Obtaining Non UE Associated Network Assistance Data Procedure

The NonUeN2MessageTransfer service operation shall be invoked by a NF Service Consumer, e.g. LMF to transfer non UE associated N2 information of N2 information class NRPPa to NG-RAN for obtaining the network assistance data.

The requirements specified in clause 5.2.2.4.1.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.4.1.1-1, the POST request body shall carry the N2 information to be transferred together with the NG RAN node identifier(s) to which the transfer needs to be initiated. The POST request body shall also include the NF Instance Identifier of the NF Service Consumer (e.g. LMF) in "nfId" attribute.

5.2.2.4.1.3 Warning Request Transfer Procedure

The NonUeN2MessageTransfer service operation shall be invoked by the NF Service Consumer, e.g. CBCF/PWS-IWF, to send non-UE specific messages of N2 information class PWS to the NG-RAN.

The requirements specified in clause 5.2.2.4.1.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.4.1.1-1, the request body shall include the N2 Message Container and:

– the globalRanNodeList IE, or;

– the taiList IE and the ratSelector IE, or;

– the ratSelector IE.

The AMF shall forward the N2 Message Container to ng-eNBs or to gNBs indicated in the globalRanNodeList IE if present. If the globalRanNodeList IE if not present, the AMF shall forward the N2 Message Container to ng-eNBs or to gNBs, subject to the value of the ratSelector IE, that serve Tracking Areas as listed in the taiList IE if present. If the taiList IE and the globalRanNodeList IE are not present, the AMF shall forward the N2 Message Container to all attached ng-eNBs or all attached gNBs, subject to the value of the ratSelector IE.

NOTE: The globalRanNodeList IE can be present when transferring WRITE-REPLACE WARNING REQUEST. When present, the globalRanNodeList IE only contains RAN nodes of the same type, i.e. only ng-eNBs or only gNBs.

The request body may additionally include the omcId IE and/or the sendRanResponse IE.

2a. Same as step 2a of Figure 5.2.2.4.1.1-1, and the POST response body shall contain the mandatory elements from the Write-Replace-Warning Confirm response (see clause 9.2.17 in TS 23.041 [20]) or the mandatory elements and optionally the unknown TAI List IE from the Stop-Warning Confirm response (see clause 9.2.19 in TS 23.041 [20]).

2b. Same as step 2b of Figure 5.2.2.4.1.1-1, and the POST response body shall contain following additional information:

– PWS specific information, if any, e.g. PWS Cause information.

5.2.2.4.1.4 Configuration Transfer Procedure

The NonUeN2MessageTransfer service operation shall be invoked by the NF Service Consumer (i.e. source AMF) towards the NF Service Producer (i.e. target AMF) to transfer the RAN configuration information received from the source NG-RAN towards the target NG-RAN.

The requirements specified in clause 5.2.2.4.1.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.4.1.1-1. The POST request body shall contain the SON Configuration Transfer IE received from the source NG-RAN, the NG RAN node identifier of the destination of this configuration information, and the N2 information class "RAN".

The target AMF shall forward the SON Configuration Transfer IE in a NGAP Downlink RAN Configuration Transfer message to the target NG-RAN.

5.2.2.4.1.5 RIM Information Transfer Procedures

The NonUeN2MessageTransfer service operation shall be invoked by the NF Service Consumer (i.e. source AMF) towards the NF Service Producer (i.e. target AMF) to transfer the RIM information received from the source NG-RAN towards the target NG-RAN.

The requirements specified in clause 5.2.2.4.1.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.4.1.1-1. The POST request body shall contain the RIM Information Transfer IE received from the source NG-RAN, the NG RAN node identifier of the destination of this configuration information, and the N2 information class "RAN".

The target AMF shall forward the RIM Information Transfer IE in a NGAP Downlink RIM Information Transfer message to the target NG-RAN.

5.2.2.4.1.6 Broadcast of Assistance Data by an LMF

The requirements specified in clause 5.2.2.4.1.1 shall apply with the following modifications:

1. Same as step 1 of Figure 5.2.2.4.1.1-1, the POST request body shall contain NRPPa-PDU IE carrying Network Assistance Data generated by LMF to be transferred together with the target NG RAN node identifier(s) to which the transfer needs to be initiated. The POST request body shall also include the NF Instance Identifier of the NF Service Consumer (e.g. LMF) in "nfId" attribute.

5.2.2.4.2 NonUeN2InfoSubscribe

5.2.2.4.2.1 General

The NonUeN2InfoSubscribe service operation is used by a NF Service Consumer (e.g. CBCF or PWS-IWF) to subscribe to the AMF for notifying non UE specific N2 information of a specific type (e.g. PWS Indications).

An NF Service Consumer (e.g. CBCF or PWS-IWF) may subscribe to notifications of specific N2 information type (e,g PWS Indications) that are not associated with any UE. In this case, the NF Service Consumer shall subscribe by using the HTTP POST method with the URI of the "Non UE N2Messages Subscriptions Collection" resource (See clause 6.1.3.9.3.1). See also Figure 5.2.2.4.2.1-1.

Figure 5.2.2.4.2.1-1 N2 Information Subscription for Non UE Information

1. The NF Service Consumer shall send a POST request to create a subscription resource in the AMF for a non UE specific N2 information notification. The payload body of the POST request shall contain:

– N2 Information Type, identifying the type of N2 information to be notified

– A callback URI for the notification

On failure or redirection, one of the HTTP status codes together with the response body listed Table 6.1.3.9.3.1-3 shall be returned.

5.2.2.4.3 NonUeN2InfoUnSubscribe

5.2.2.4.3.1 General

The NonUeN2InfoUnSubscribe service operation is used by a NF Service Consumer (e.g. CBCF or PWS-IWF) to unsubscribe to the AMF to stop notifying N2 information of a specific type (e.g. PWS Indications).

The NF Service Consumer shall use the HTTP method DELETE with the URI of the "Non UE N2 Message Notification Individual Subscription" resource (See clause 6.1.3.10.3.1), to request the deletion of the subscription for non UE specific N2 information notification, towards the AMF. See also Figure 5.2.2.4.3.1-1.

Figure 5.2.2.4.3.1-1 NonUeN2InfoUnSubscribe for Non UE Specific Information

1. The NF Service Consumer shall send a DELETE request to delete an existing subscription resource in the AMF.

2. If the request is accepted, the AMF shall reply with the status code 204 indicating the resource identified by subscription ID is successfully deleted, in the response message.

On failure or redirection, one of the HTTP status codes together with the response body listed Table 6.1.3.10.3.1-3 shall be returned.

5.2.2.4.4 NonUeN2InfoNotify

5.2.2.4.4.1 General

The NonUeN2InfoNotify service operation is used during the following procedures:

– Obtaining non-UE associated network assistance data (See clause 4.13.5.6 in 3GPP TS 23.502 [3])

– Receiving PWS related events from the NG-RAN

– Broadcast of Assistance Data by an LMF (see clause 6.14.1 of 3GPP TS 23.273 [42]).

The NonUeN2InfoNotify service operation is invoked by the AMF to notify a NF Service Consumer that subscribed Non-UE N2 information has been received from the 5G-AN.

The AMF shall use HTTP POST method to the N2Info Notification URI provided by the NF Service Consumer via NonUeN2InfoSubscribe service operation (See clause 5.2.2.4.2). See also Figure 5.2.2.4.4.1-1.

Figure 5.2.2.4.4.1-1 Non-UE N2 Information Notify

1. The AMF shall send a HTTP POST request to the N2Info Notification URI, and the payload body of the POST request shall contain a N2INformationNotification data structure, with the N2 information that was subscribed by the NF Service Consumer.

2a. On success, "204 No Content" shall be returned and the payload body of the POST response shall be empty.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.5.3.3.1-3 shall be returned. The message body shall contain a ProblemDetails object with "cause" set to one of the corresponding application errors listed in Table 6.1.5.3.3.1-3.

5.2.2.4.4.2 Using NonUeN2InfoNotify during Location Services procedures

The NonUeN2InfoNotify service operation is invoked by a NF Service Producer, i.e. the AMF, towards the NF Service Consumer, e.g. the LMF, to notify the assistance data received from the 5G-AN.

The requirements specified in clause 5.2.2.4.4.1 shall apply with the following modifications:

1. If the corresponding N2 notification URI is not available, the AMF shall retrieve the NF profile of the NF Service Consumer (e.g. the LMF) from the NRF using the NF Instance Identifier received during "Obtaining Non UE Associated Network Assistance Data Procedure" or "Broadcast of Assistance Data by an LMF Procedure" (see clause 5.2.2.4.1.2), and further identify the corresponding service instance if Service Instance Identifier was also received, and fetch N2 Notification URI from the default subscription registered with "N2_INFORMATION" notification type and "NRPPa" information class (See Table 6.2.6.2.3-1 and Table 6.2.6.2.4-1 of 3GPP TS 29.510 [29]).

2. Same as step 1 of Figure 5.2.2.4.4.1-1, the payload shall contain network assistance data.

5.2.2.4.4.3 Use of NonUeN2InfoNotify for PWS related events

The NonUeN2InfoNotify service operation shall be used during the following PWS related events:

1) The AMF has received a Write-Replace-Warning-Response or a PWS-Cancel-Response from the NG-RAN over N2.

Upon receiving the N2 Message Content the RAN Nodes return a response which may include the Broadcast Completed Area List IE or the Broadcast Cancelled Area List IE, depending on the Message Type IE. The AMF may aggregate the lists it receives from the RAN Nodes for the same request.

If the Send-Write-Replace-Warning Indication IE was present in the Write-Replace-Warning Request message, then the AMF may forward the Broadcast Completed Area List IE(s) to the NF Service Consumer. If the NG-RAN node(s) have responded without the Broadcast Completed Area List IE then the AMF shall include the NG-RAN node ID(s) in "bcEmptyAreaList" attribute in the request body.

If the Send-Stop-Warning Indication IE was present in the Stop-Warning-Request message, then the AMF may forward the Broadcast Cancelled Area List IE(s) to the NF Service Consumer. If the NG-RAN node(s) have responded without the Broadcast Cancelled Area List IE then the AMF shall include the NG-RAN node ID(s) in "bcEmptyAreaList" attribute in the request body.

2) The AMF has received a Restart Indication or a Failure Indication from a NG-RAN Node. The AMF shall forward the Restart Indication or Failure Indication to the NF Service Consumer.

The requirements specified in clause 5.2.2.4.4.1 shall apply with the following modifications:

– Same as step 1 of Figure 5.2.2.4.4.1-1, the request body shall include the PWS related N2 information.

5.2.2.5 AMF Status Change Operations

5.2.2.5.1 AMFStatusChangeSubscribe

5.2.2.5.1.1 General

This service operation is used by a NF Service Consumer to subscribe the status change of the AMF.

The AMFStatusChangeSubscribe service operation is used during the following procedure:

– AMF planned removal procedure (see 3GPP TS 23.501 [2], clause 5.21.2.2)

5.2.2.5.1.2 Creation of a subscription

This service operation creates a subscription so a NF Service Consumer can request to be notified when the status of the AMF is changed.

It is executed by creating a new individual resource under the collection resource "subscriptions". The operation shall be invoked by issuing a POST request on the URI of the "subscriptions collection" resource (See clause 6.1.3.6.3.1).

Figure 5.2.2.5.1.1-1 NF Service Consumer Subscription to Notifications

1. The NF Service Consumer shall send a POST request to the resource URI representing the "subscriptions" collection resource. The request body shall include the data indicating the GUAMI(s) supported by the AMF that the NF Service Consumer is interested in receiving the related status change notification. The request body also contains a callback URI, where the NF Service Consumer shall be prepared to receive the actual notification from the AMF (see AMFStatusChangeNotify operation in clause 5.2.2.5.3).

2a. On success, the AMF shall include a HTTP Location header to provide the location of a newly created resource (subscription) together with the status code 201 indicating the requested resource is created in the response message.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.6.3.1-3 shall be returned. For a 4xx/5xx response, the message body containing a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.6.3.1-3.

5.2.2.5.1.3 Modification of a subscription

This service operation updates the subscription data of an NF Service Consumer previously subscribed in the AMF by providing the updated subscription data to the AMF. The update operation shall apply to the whole subscription data (complete replacement of the existing subscription data by a new subscription data).

The NF Service Consumer shall issue an HTTP PUT request, towards the URI of the "individual subscription" resource (See clause 6.1.3.7.3.2), as shown in Figure 5.2.2.5.1.3-1:

Figure 5.2.2.5.1.3-1 Subscription Data Complete Replacement

1. The NF Service Consumer shall send a PUT request to the resource URI representing the individual subscription. The request body shall include a representation of subscription data to replace the previous subscription data in the AMF.

2a. On success, "200 OK" shall be returned, the payload body of the PUT response shall contain the representation of the replaced resource. "204 No Content" may be returned, if the NF Service Producer accepts entirely the resource representation provided by the NF Service Consumer in the request.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.7.3.2-3 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.7.3.2-3.

5.2.2.5.2 AMFStatusChangeUnSubscribe

5.2.2.5.2.1 General

This service operation removes an existing subscription to notifications.

The AMFStatusChangeUnSubscribe service operation is used during the following procedure:

– AMF planned removal procedure (see 3GPP TS 23.501 [2], clause 5.21.2.2)

It is executed by deleting a given resource identified by a "subscriptionId". The operation is invoked by issuing a DELETE request on the URI of the specific " individual subscription" resource (See clause 6.1.3.7.3.1).

Figure 5.2.2.5.2.1-1: NF Service Consumer Unsubscription to Notifications

1. The NF Service Consumer shall send a DELETE request to the resource URI representing the individual subscription. The request body shall be empty.

2a. On success, "204 No Content" shall be returned. The response body shall be empty.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.7.3.1-3 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.7.3.1-3.

5.2.2.5.3 AMFStatusChangeNotify

5.2.2.5.3.1 General

This service operation notifies each NF Service Consumer that was previously subscribed to receiving notifications of the status change of the AMF (e.g. AMF unavailable). The notification is sent to a callback URI that each NF Service Consumer provided during the subscription (see AMFStatusChangeSubscribe operation in 5.2.2.5.1).

The AMFStatusChangeNotify service operation is used during the following procedure:

– AMF planned removal procedure (see 3GPP TS 23.501 [2], clause 5.21.2.2)

The operation is invoked by issuing a POST request to each callback URI of the different NF Service Consumer.

Figure 5.2.2.5.3.1-1: AMF Notifications

1. The AMF shall send a POST request to the callback URI. The request body shall include the GUAMI(s) and the related status change, GUAMI(s) is indicated by the NF Service Consumer during the subscription operation. For network deployment without UDSF case, the target AMF Name which is to serve the user of the indicated GUAMI(s) is also included.

2a. On success, "204 No content" shall be returned by the NF Service Consumer.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.5.2.3.1-2 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.5.2.3.1-2.

5.2.2.6 EBIAssignment

5.2.2.6.1 General

The EBIAssignment service operation is used during the following procedures (see 3GPP TS 23.502 [3], clause 4.11.1.4):

– UE requested PDU Session Establishment including Request Types "Initial Request", "Existing PDU Session", "Initial emergency request" and "Existing emergency PDU session" (Non-roaming and Roaming with Local Breakout (see 3GPP TS 23.502 [3], clause 4.3.2.2.1).

– UE requested PDU Session Establishment including Request Types "Initial Request" and "Existing PDU Session" (Home-routed Roaming (see 3GPP TS 23.502 [3], clause 4.3.2.2.2).

– UE or network requested PDU Session Modification (non-roaming and roaming with local breakout) (see 3GPP TS 23.502 [3], clause 4.3.3.2).

– UE or network requested PDU Session Modification (home-routed roaming) (see 3GPP TS 23.502 [3], clause 4.3.3.3).

– UE Triggered Service Request (see 3GPP TS 23.502 [3], clause 4.2.3.2) to move PDU Session(s) from untrusted non-3GPP access to 3GPP access.

– Network requested PDU Session Modification, when the SMF needs to release the assigned EBI from a QoS flow (see 3GPP TS 23.502 [3], clause 4.11.1.4.3).

The EBIAssignment service operation is invoked by a NF Service Consumer, e.g. a SMF, towards the NF Service Producer, i.e. the AMF, to request the AMF to allocate EPS bearer ID(s) towards EPS bearer(s) mapped from QoS flow(s) for an existing PDU Session for a given UE.

EBI allocation shall apply only to:

– QoS flows of Single Access PDU Session(s) via 3GPP access supporting EPS interworking with N26;

– Qos flows of Multi-Access PDU Session(s) supporting EPS interworking with N26, that are not only allowed over non-3GPP access.

EBI allocation shall not apply to:

– PDU Session(s) via 3GPP access supporting EPS interworking without N26, or;

– PDU Session(s) via non-3GPP access supporting EPS interworking;

– GBR QoS flow(s) that are only allowed over non-3GPP access in Multi-Access PDU Session(s) supporting EPS interworking.

The EBIAssignment service operation is also invoked by an NF Service Consumer, e.g. an SMF, towards the NF Service Producer supporting the EAEA feature, i.e. the AMF, to request the AMF to update the mapping of EBI and ARP, if the ARP for a QoS flow that has already been allocated an EBI is changed during the network requested PDU Session Modification.

The NF Service Consumer (e.g. the SMF) shall perform EBIAssignment service operation by invoking "assign-ebi" custom operation on the "individual ueContext" resource (See clause 6.1.3.2.4.3). See also Figure 5.2.2.6.1-1.

Figure 5.2.2.6.1-1 EBI Assignment

1. The NF Service Consumer, e.g. the SMF, shall invoke "assign-ebi" custom method on individual ueContext resource, which is identified by the UE’s SUPI or PEI in the AMF. The NF Service consumer shall provide PDU Session ID and ARP list as input for the service operation. If the NF Service Consumer invokes this service operation to update the mapping of EBI and ARP for a QoS flow to which an EBI is already allocated in the AMF, the NF Service Consumer shall provide the PDU Session ID and modifiedEbiList.

2a. On success, the AMF shall assign EBI for each ARP in received ARP list, if enough EBI(s) are available. If there is not enough EBI(s) available, the AMF may revoke already assigned EBI(s) based on the ARP(s) and the S-NSSAI of the PDU session for which the request was received, EBIs information in the UE context and local policies. The AMF may only assign a subset of the requested EPS Bearer ID(s), e.g. when other PDU Sessions with higher ARP have occupied other available EPS Bearer IDs. If AMF has successfully assigned all or part of the requested EBI(s), the AMF shall respond with the status code 200 OK, together with the assigned EBI to ARP mapping(s), the list of ARPs for which the AMF failed to allocate an EBI (if any) and the list of EBI(s) released for this PDU session due to revocation based on ARP(s) and the S-NSSAI (if any).

If the request contains "releasedEbiList", the AMF shall release the requested EBI(s). The AMF shall respond with the status code 200 OK and shall include the EBI(s) released in the "releasedEbiList" IE of the POST response body. The "releasedEbiList" in the request shall be handled before the EBI assignment in AMF.

If the same EBI(s) are both in the "releasedEbiList"and "assignedEbiList", the NF sevice consumer considers that EBI(s) have been released and reassigned.

If the request contains "modifiedEbiList", the AMF shall store the association of the assigned EBI and ARP pair to the corresponding PDU Session ID. The AMF shall respond with the status code 200 OK and shall include the EBI(s) with ARP updated in the "modifiedEbiList" IE of the POST response body.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.1.3.2.4.3.2-2 shall be returned. For a 4xx/5xx response, the message body shall contain an AssignEbiError structure, including:

– a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.1.3.2.4.3.2-2;

– a failureDetails which describes the details of the failure including the list of ARPs for which the EBI assignment failed.