4 Npcf_AMPolicyAuthorization Service

29.5343GPP5G SystemAccess and Mobility Policy Authorization ServiceRelease 18Stage 3TS

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

4.1 Service Description

4.1.1 Overview

The Npcf_AMPolicyAuthorization service, as defined in 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14], is provided by the Policy Control Function (PCF) and enables an authorized NF service consumer to influence access and mobility policies for a UE and to subscribe to notifications on UE 5G ProSe Policy event(s).

The Npcf_AMPolicyAuthorization service enables to authorize a NF service consumer’s request and create/update the associated access and mobility policies as requested by the authorized NF service consumer for the Access and Mobility policy association to which the NF service consumer AM context (e.g. the AF application AM context) is bound.

This service also allows the NF service consumer to subscribe/unsubscribe to notifications on AM Policy event(s) (e.g. service area restrictions policy change) and to subscribe/unsubscribe to notifications on UE 5G ProSe Policy event(s) (e.g. PDUID change event).

4.1.2 Service Architecture

The 5G System Architecture is defined in 3GPP TS 23.501 [2]. The Policy and Charging control related 5G architecture is also defined in 3GPP TS 23.503 [14] and 3GPP TS 29.513 [15].

The known NF service consumers of the Npcf_AMPolicyAuthorization service are the Application Function (AF), the Network Exposure Function (NEF), the 5G Direct Discovery Name Management Function (5G DDNMF) and the Time Sensitive Communication and Time Synchronization Function (TSCTSF).

The Npcf_AMPolicyAuthorization service is provided by the PCF and consumed by the NF service consumers (e.g. AF, NEF), as shown in figure 4.1.2-1 for the SBI representation model and in figure 4.1.2-2 for the reference point representation model.

Figure 4.1.2-1: Npcf_AMPolicyAuthorization service architecture, SBI representation

Figure 4.1.2-2: Npcf_AMPolicyAuthorization service architecture, reference point representation

In the case of an Untrusted AF, i.e. when the AF interacts with the PCF via the NEF, the NEF may interact with the PCF via the N30 reference point in the same way that the AF interacts with the PCF via the N5 reference point.

4.1.3 Network Functions

4.1.3.1 Policy Control Function (PCF)

The PCF (Policy Control Function) is a functional element that encompasses, among other functionalities, access and mobility policy decisions for the control of e.g. the UE Service Area Restrictions and RAT/RFSP control, and the delivery of UE Policies (e.g. UE 5G ProSe Policies) to the UE.

The PCF receives from a NF service consumer (e.g. AF, NEF) access and mobility service requirements related to a registered UE and notifies it about the outcome of the requested access and mobility policy changes, if applicable, if the NF service consumer previously subscribed, via the Npcf_AMPolicyAuthorization service.

The PCF derives access and mobility policies and provisions them to the AMF via the Npcf_AMPolicyControl as described in 3GPP TS 29.507 [16].

When the PCF that handles the AM Policy Associations (PCF for the UE) is different from the PCF that handles the SM Policy Associations (PCF for the PDU session) for a UE, the PCF subscribes to application traffic detection event(s) using the Npcf_PolicyAuthorization service as described in 3GPP TS 29.514 [17].

The PCF receives from a NF service consumer (e.g. 5G DDNMF) subscriptions to notifications on events related to the delivered UE 5G ProSe Policies for a SUPI.

4.1.3.2 NF Service Consumers

The known NF service consumers are the AF, the NEF, the 5G DDNMF, and the TSCTSF as defined in 3GPP TS 23.502 [3].

The Application Function (AF) is a network function offering, among other functionalities, control to applications for the dynamic change of access and mobility policies for a registered UE. The AF uses the Npcf_AMPolicyAuthorization service to provide to the PCF service information related to the required access and mobility context (e.g. access and mobility required policies) for the concerned service(s).

The AFs can be deployed by the same operator offering the access services or be provided by an external third-party service provider. If the AF is not allowed by the operator to directly access the PCF, the AF uses the 3GPP external network exposure framework via the NEF to interact with the PCF, as described in clause 5.20 of 3GPP TS 23.501 [2].

The Network Exposure Function (NEF) supports external exposure of the capabilities of 5GC network functions.

The 5G DDNMF is a network function that handles the network related actions required for dynamic 5G ProSe Direct Discovery, as defined in 3GPP TS 23.304 [22].

The AF trusted by the operator, or the NEF can use the TSCTSF to interface with the PCF to support the delivery of access stratum time distribution information to the AMF as defined in 3GPP TS 29.565 [25].

4.2 Service Operations

4.2.1 Introduction

Service operations defined for the Npcf_AMPolicyAuthorization service are shown in table 4.2.1-1.

Table 4.2.1-1: Npcf_AMPolicyAuthorization Service Operations

Service Operation Name	Description	Initiated by
Npcf_AMPolicyAuthorization_Create	Creates an AF application AM context in the PCF as per request from an authorized NF service consumer, and determines and installs the access and mobility policy according to the service information provided by the NF service consumer. It also allows the subscription to event notifications.	NF service consumer (e.g. AF, NEF, TSCTSF)
Npcf_AMPolicyAuthorization_Update	Updates the AF application AM context in the PCF as per request from an authorized NF service consumer, and determines and updates the access and mobility policy according to the modified service information provided by the NF service consumer. It also allows the update of the associated subscription to event notifications.	NF service consumer (e.g. AF, NEF, TSCTSF)
Npcf_AMPolicyAuthorization_Delete	Provides means to the concerned NF service consumer to delete the AF application AM context in the PCF.	NF service consumer (e.g. AF, NEF, TSCTSF)
Npcf_AMPolicyAuthorization_Subscribe	Allows NF service consumers to subscribe to event notifications.	NF service consumer (e.g. AF, NEF, 5G DDNMF)
Npcf_AMPolicyAuthorization_Unsubscribe	Allows NF service consumers to unsubscribe from event notifications.	NF service consumer (e.g. AF, NEF, 5G DDNMF)
Npcf_AMPolicyAuthorization_Notify	Notifies NF service consumers of the subscribed events.	PCF

NOTE 1: The NEF and the AF use the Npcf_AMPolicyAuthorization service in the same way.

NOTE 2: The 5G DDNMF only uses the Npcf_AMPolicyAuthorization subscribe, unsubscribe and notify service operations.

NOTE 3: The TSCTSF only uses the Npcf_AMPolicyAuthorization create, update and delete service operations.

4.2.2 Npcf_AMPolicyAuthorization_Create service operation

4.2.2.1 General

The Npcf_AMPolicyAuthorization_Create service operation authorizes the request from the NF service consumer, and optionally communicates with Npcf_AMPolicyControl service to determine and install in the AMF the access and mobility policies according to the information provided by the NF service consumer.

The Npcf_AMPolicyAuthorization_Create service operation creates a NF service consumer related AM context in the PCF.

The following procedures using the Npcf_AMPolicyAuthorization_Create service operation are supported:

– Initial provisioning of access and mobility related service information.

– Creation of the subscription to service area coverage change outcome.

4.2.2.2 Initial provisioning of access and mobility related service information

This procedure is used to set up an NF service consumer AM context (e.g. an AF application AM context) for the service as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.2.2-1 illustrates the initial provisioning of service information for the AM context.

Figure 4.2.2.2-1: Initial provisioning of service information for the AM context

When a NF service consumer requires an AM context is being established in the 5GS and the related access and mobility requirements are available at the NF service consumer, the NF service consumer shall invoke the Npcf_AMPolicyAuthorization_Create service operation by sending the HTTP POST request to the resource URI representing the "Application AM contexts" collection resource of the PCF, as shown in figure 4.2.2.2-1, step 1.

The NF service consumer shall include in the "AppAmContextData" data type in the payload body of the HTTP POST request a partial representation of the "Individual Application AM Context" resource, that shall include:

– the notification URI where the PCF requests to the NF service consumer the termination of the application AM context encoded as "termNotifUri" attribute;

– the SUPI of the UE to which the AF requested policy shall apply encoded as "supi" attribute;

– when the NF service consumer is the NEF or the AF:

a. the indication that high throughput policy is desired for the indicated UE encoded as "highThruInd" attribute; and/or

b. the service area coverage desired for the indicated UE encoded as "covReq" attribute, that contains a list of Tracking Area codes per serving network where the requested service shall be allowed;

– when the NF service consumer is the TSCTSF:

a. the access stratum time distribution parameters (5G access stratum time distribution indication (enable, disable), and/or Uu time synchronization error budget) encoded as "asTimeDisParam" attribute.

In the "AppAmContextData" data type in the payload body of the HTTP POST request, the NF service consumer may include, when the NF service consumer is the NEF or the AF:

– the GPSI of the UE encoded as "gpsi" attribute; and/or

– the expiration time of the AF requested policy encoded as "expiry" attribute.

The NF service consumer may also include the "evSubsc" attribute of "AmEventsSubscData" data type to request the notification of access and mobility policy changes events. The NF service consumer shall include within the "evSubsc" attribute:

– the notification URI where the NF service consumer receives the events notification encoded as "eventNotifUri" attribute; and

– the events to subscribe to in the "events" attribute. For each subscribed event in the "events" attribute, the NF service consumer shall include the event identifier within the "event" attribute and may include the description of the event reporting mode as specified in clause 4.2.5.2.

The events subscription data is provisioned in the "AM Policy Events Subscription" sub-resource.

The NF service consumer may include within the "evSubsc" attribute specific per event subscription information, if applicable, and as described in clause 4.2.2.3.

If the PCF cannot successfully fulfil the received HTTP POST request due to the internal PCF error or due to the error in the HTTP POST request, the PCF shall send the HTTP error response as specified in clause 5.7.

Otherwise, when the PCF receives the HTTP POST request from the NF service consumer, the PCF shall bind the Individual application AM context to the concerned AM policy association. The PCF identifies the AM policy association for which the HTTP POST request applies with the SUPI provided in the "supi" attribute within the body of the HTTP POST request:

If the PCF fails in executing the binding with the AM policy association, the PCF shall reject the HTTP POST request with an HTTP "500 Internal Server Error" response and may include the "cause" attribute set to "POLICY_ASSOCIATION_NOT_AVAILABLE".

The PCF shall check whether the received access and mobility related service information requires access and mobility policies to be created and provisioned in the AMF. Provisioning of access and mobility policies shall be carried out as specified at 3GPP TS 29.507 [16].

If the PCF created an "Individual Application AM Context" resource, the PCF shall send to the NF service consumer a "201 Created" response to the HTTP POST request, as shown in figure 4.2.2.2-1, step 2. The PCF shall include in the "201 Created" response:

– a Location header field; and

– an "AppAmContextRespData" data type in the payload body.

The Location header field shall contain the URI of the created Individual application AM context resource i.e. "{apiRoot}/npcf-am-policyauthorization/<apiVersion>/app-am-contexts/{appAmContextId}".

The "AppAmContextRespData" data type payload body shall contain the representation of the created "Individual application AM context" resource within the "AppAmContextData" data type. When the request included event subscription information:

– the "AppAmContextData" data type shall also include the "AM Policy Events Subscription" sub-resource representation within the "evSubsc" attribute; and

– when the NF service consumer requested the immediate reporting and the current value is available, the "AppAmContextRespData" data type shall include the corresponding event(s) notification, encoding the event identifier within the "repEvents" attribute and the applicable event(s) information as specified within the "AmEventsNotification" data type.

The acknowledgement towards the NF service consumer should take place before or in parallel with any required access and mobility policy provisioning towards the AMF.

NOTE: The behaviour when the NF service consumer does not receive the HTTP response message, or when it arrives after the internal timer waiting for it has expired, or when it arrives with an indication different than a success indication, are outside the scope of this specification and is based on operator policy.

4.2.2.3 Creation of the subscription to service area coverage change outcome

This procedure is used by a NF service consumer to subscribe to notifications about whether the requested service area coverage provided in the access and mobility service information has been provisioned as the corresponding Service Area Restrictions to the AMF or cannot be provisioned to the AMF. This procedure also enables the subscription to notifications about subsequent changes on the service area coverage result of changes of the provisioned Service Area Restrictions (e.g. due to changes in the subscribed Service Area Restrictions).

To request to the PCF to provide a notification when a service area coverage (which may be same or different service area coverage from the service area coverage provided by the NF service consumer) has been determined (and the related policy for Service Area Restrictions is applied) based on the request or when a service area coverage cannot be determined and, additionally, when the service area coverage subsequently changes within the AM Policy Association, the NF service consumer shall provide in the HTTP POST request message described in clause 4.2.2.2 the "evSubsc" attribute including an event entry within the "events" attribute with the "event" attribute set to "SAC_CH" and the "notifMethod" set to "ON_EVENT_DETECTION" (or omitted).

The PCF shall reply to the NF service consumer as described in clause 4.2.2.2.

When the service area coverage change event is met in the PCF, the PCF notifies to the NF service consumer as described in clause 4.2.7.4.

4.2.3 Npcf_AMPolicyAuthorization_Update service operation

4.2.3.1 General

The Npcf_AMPolicyAuthorization_Update service operation provides updated application level information from the NF service consumer and optionally communicates with the Npcf_AMPolicyControl service to determine and install the access and mobility policies according to the information provided by the NF service consumer.

The Npcf_AMPolicyAuthorization_Update service operation updates an AF application AM context in the PCF.

The following procedures using the Npcf_PolicyAuthorization_Update service operation are supported:

– Modification of AM related service information.

– Modification of the subscription to service area coverage change outcome.

4.2.3.2 Modification of AM related service information

This procedure is used to modify an existing AF application AM context as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.3.2-1 illustrates the modification of access and mobility service information using HTTP PATCH method.

Figure 4.2.3.2-1: Modification of access and mobility service information using HTTP PATCH

The NF service consumer may modify the AF application AM context information at any time (e.g. due to an AF application AM context modification or an internal NF service consumer trigger) and invoke the Npcf_AMPolicyAuthorization_Update service operation by sending an HTTP PATCH request message to the resource URI representing the concerned "Individual application AM context" resource, as shown in figure 4.2.3.2-1, step 1, with the modifications to apply.

The JSON body within the PATCH request shall include the "AppAmContextUpdateData" data type and shall be encoded according to "JSON Merge Patch", as defined in IETF RFC 7396 [18].

The NF service consumer may create, modify or remove access and mobility service information by including updated values within the "AppAmContextUpdateData" data type as follows:

– the NF service consumer may update the "termNotifUri" attribute, to request that subsequent termination notifications are sent to a new NF service consumer;

– the NF service consumer may create or update the previously provided access and mobility service information, e.g. when the NF service consumer is the AF/NEF, expiration time, high throughput indication and/or service area coverage information, or, when the NF service consumer is the TSCTSF, 5G access stratum time distribution indication (enable, disable), and/or Uu time synchronization error budget (see clause 4.2.2.2); and

– the NF service consumer may delete the previously provided attribute(s), e.g. when the NF service consumer is the AF/NEF, expiration time, high throughput indication and/or service area coverage information, or, when the NF service consumer is the TSCTSF, Uu time synchronization error budget, by setting them to null value, to indicate that the previously provided access and mobility service information no longer applies.

The NF service consumer may also create, modify or remove events subscription information by sending an HTTP PATCH request message to the resource URI representing the concerned "Individual application AM context" resource.

The NF service consumer shall create event subscription information by including the "evSubsc" attribute of "AmEventsSubscDataRm" data type with the corresponding list of events to subscribe to within the "events" attribute, and the callback URI where to receive the event notifications within the "eventNotifUri" attribute. For each subscribed event in the "events" attribute, the NF service consumer shall include the event identifier within the "event" attribute and may include the description of the event reporting mode as specified in clause 4.2.5.2.

The NF service consumer shall update existing event subscription information by including an updated value of the "evSubsc" attribute of the "AmEventsSubscDataRm" data type as follows:

– the "eventNotifUri" attribute may include an updated value of the callback URI;

– the "events" attribute shall include the new complete list of subscribed events; and

NOTE: When the NF service consumer requests to remove an event, this event is not included in the "events" attribute.

– the per specific event subscription information is included/removed, if applicable, and as described in clause 4.2.3.3.

The NF service consumer shall remove existing event subscription information by setting to null the "evSubsc" attribute.

If the service information provided in the body of the HTTP PATCH request is rejected because the requested policy for the AM context is invalid or insufficient for the PCF to perform the requested action because the service area coverage and/or high throughput policies present in the request result in an Individual application AM context without service area coverage and high throughput requested policies, or the request indicates the deletion of the 5G access stratum time distribution parameters resulting in an Individual application AM context without 5G access stratum time distribution and Uu time synchronization error budget requested policies, the PCF may indicate in an HTTP "400 Bad Request" response message the cause for the rejection including the "cause" attribute set to "INVALID_POLICY_REQUEST".

If the PCF cannot successfully fulfil the received HTTP PATCH request due to the internal PCF error or due to the error in the HTTP PATCH request, the PCF shall send the HTTP error response as specified in clause 5.7.

If the PCF determines the received HTTP PATCH request needs to be redirected, the PCF shall send an HTTP redirect response as specified in clause 6.10.9 of 3GPP TS 29.500 [4].

If the request is accepted, the PCF shall update the AM related service information with the new information received and/or update the associated AM events subscription. Due to the updated service information and/or AM events subscription, the PCF may need to create, modify or delete the related access and mobility policies and provide the updated information towards the AMF following the corresponding procedures specified in 3GPP TS 29.507 [16].

The PCF shall reply to the NF service consumer with an HTTP "200 OK" response message and include the "AppAmContextRespData" data type payload body which shall include:

– the representation of the modified "Individual Application AM Context" resource within the "AppAmContextData" data type; and

– when the request included the creation or the update of the subscription to notification event(s):

a) the representation of the "AM Policy Events Subscription" sub-resource within the "evSubsc" attribute included in the "AppAmContextData" data type; and

b) when the NF service consumer requested the immediate reporting of the new subscribed event(s) and the current value(s) is available, "AppAmContextRespData" data type shall include the corresponding event(s) notification encoding the event identifier within "repEvents" attribute and the applicable event(s) information as specified within the "AmEventsNotification" data type.

The HTTP response message towards the NF service consumer should take place before or in parallel with any required access and mobility policy provisioning towards the SMF.

4.2.3.3 Modification of the subscription to service area coverage change outcome

This procedure is used by a NF service consumer to subscribe to notifications about whether an updated service area coverage (which may be same or different service area coverage from the service area coverage provided by the NF service consumer) determined from the requested service area coverage provided in the access and mobility service information has been applied as the corresponding Service Area Restrictions or whether an updated service area coverage cannot be provisioned. This procedure also enables to modify or remove a previous subscription to service area coverage changes.

The NF service consumer shall include in the HTTP PATCH request message described in clause 4.2.3.2 the "evSubsc" attribute as encoded as follows:

– To create a subscription (i.e., the subscription to the "SAC_CH" event does not exist in the PCF) the NF service consumer shall include the "evSubsc" attribute encoded as specified in clause 4.2.2.3.

– To modify an existing subscription, (i.e., the subscription to the "SAC_CH" event exists in the PCF) the NF service consumer shall include within the "evSubsc" attribute the "events" attribute with the updated subscription information for the "event" attribute set to "SAC_CH" as specified in clause 4.2.2.3.

– To remove an existing subscription (i.e., the subscription to the "SAC_CH" event exists in the PCF):

a. If there are other events whose subscription the NF service consumer wants to keep, the NF service consumer shall include the "events" attribute without any event entry with the "event" attribute set to "SAC_CH".

b. If there are no other events whose subscription the NF service consumer wants to keep, the NF service consumer shall set to null the "evSubsc" attribute.

The PCF shall reply to the NF service consumer as described in clause 4.2.3.2.

When the service area coverage change event is met in the PCF, the PCF notifies to the NF service consumer as described in clause 4.2.7.4.

NOTE: When the previously provided service area coverage requirements are completely removed by the NF service consumer, or the requested service area coverage policy expires, the NF service consumer should also unsubscribe to SAC_CH event to prevent the stale subscription information from remaining on the PCF.

4.2.4 Npcf_AMPolicyAuthorization_Delete service operation

4.2.4.1 General

The Npcf_AMPolicyAuthorization_Delete service operation provides means for the NF service consumer to delete the AF application AM context.

The following procedures using the Npcf_AMPolicyAuthorization_Delete service operation are supported:

– AF application AM context termination.

4.2.4.2 AF application AM context termination

This procedure is used to terminate an AF application AM context as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.4.2-1 illustrates the AF application AM context termination.

Figure 4.2.4.2-1: AF application AM context termination

When an AF session is terminated, and if the AF application AM context was created as described in clause 4.2.2, the NF service consumer shall invoke the Npcf_AMPolicyAuthorization_Delete service operation to the PCF using an HTTP DELETE request, as shown in figure 4.2.4.2-1, step 1.

The NF service consumer shall set the request URI to "{apiRoot}/npcf-am-policyauthorization/<apiVersion>/app-am-contexts/{appAmContextId}".

When the PCF receives the HTTP DELETE request from the NF service consumer, indicating the termination of the AF application AM context information, if the HTTP DELETE request from the NF service consumer is accepted, the PCF shall acknowledge that request by sending to the NF service consumer a "204 No Content".

Afterwards, the PCF shall determine whether the access and mobility policies of the concerned UE need to be updated or not. If the PCF determines that an update is needed, the PCF shall initiate the update of the access and mobility policies of the concerned UE as per the procedures specified in 3GPP TS 29.507 [16].

If the HTTP DELETE request from the NF service consumer is not accepted, the PCF shall indicate in the response to HTTP DELETE request the cause for the rejection as specified in clause 5.7.

If the PCF determines the received HTTP DELETE request needs to be redirected, the PCF shall send an HTTP redirect response as specified in clause 6.10.9 of 3GPP TS 29.500 [4].

4.2.5 Npcf_AMPolicyAuthorization_Subscribe service operation

4.2.5.1 General

The Npcf_AMPolicyAuthorization_Subscribe service operation enables to manage subscriptions to events for an existing AF application AM context. The Npcf_AMPolicyAuthorization_Subscribe service operation also enables to manage subscriptions to events without an existing AF application AM context.

Such subscriptions to events shall be created:

– within the AF application AM context establishment procedure by invoking the Npcf_AMPolicyAuthorization_Create service operation, as described in clause 4.2.2;

– within the AF application AM context modification procedure by invoking the Npcf_AMPolicyAuthorization_Update service operation, as described in clause 4.2.3; or

– by invoking the Npcf_AMPolicyAuthorization_Subscribe service operation for the existing AF application AM context, as described in clause 4.2.5.2.

– by invoking the Npcf_AMPolicyAuthorization_Subscribe service operation when there is no existing Individual application AM context and the NF service consumer does not provide Access and Mobility related service information, as described in clause 4.2.5.3.

The following procedures using the Npcf_AMPolicyAuthorization_Subscribe service operation is supported:

– Subscription to events for an existing AF application AM context.

– Subscription to events without an existing AF application AM context.

– Subscription to PDUID changes.

4.2.5.2 Handling of subscription to events for the existing AF application AM context

This procedure is used to create a subscription to events for the existing AF application AM context or to modify an existing subscription, as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.5.2-1 illustrates the creation of events subscription information using HTTP PUT method.

Figure 4.2.5.2-1: Creation of events subscription information using HTTP PUT

Figure 4.2.5.2-2 illustrates the modification of events subscription information using HTTP PUT method.

Figure 4.2.5.2-2: Modification of events subscription information using HTTP PUT

When the NF service consumer decides to create a subscription to one or more events for the existing AF application AM context or to modify an existing subscription previously created by itself at the PCF, the NF service consumer shall invoke the Npcf_AMPolicyAuthorization_Subscribe service operation by sending the HTTP PUT request to the resource URI representing the "AM Policy Events Subscription" sub-resource in the PCF, as shown in figure 4.2.5.2-1, step 1 and figure 4.2.5.2-2, step 1.

NOTE 1: The NF service consumer builds the "AM Policy Events Subscription" sub-resource URI by adding the path segment "/events-subscription" at the end of the resource URI of the "Individual application AM context" resource, received in the Location header field of the resource creation response as specified in clause 4.2.2.2.

The NF service consumer shall provide in the "AmEventsSubscData" data type of the body of the HTTP PUT request:

– the "events" attribute with the list of events to be subscribed; and

– the "eventNotifUri" attribute, that includes the callback URI where the PCF shall send the notification of the subscribed events.

NOTE 2: The "eventNotifUri" attribute within the "AmEventsSubscData" data structure can be modified to request that subsequent notifications are sent to a new NF service consumer.

For each subscribed event included in the "events" attribute, the NF service consumer type shall include the event identifier within the "event" attribute and may include the description of the event reporting mode, as follows:

a. immediate reporting indication as "immRep" attribute;

b. event notification method (periodic, one time, on event detection) as "notifMethod" attribute;

c. maximum number of reports as "maxReportNbr" attribute;

d. monitoring Duration as "monDur" attribute; and/or

e. repetition period for periodic reporting as "repPeriod" attribute.

The NF service consumer may provide within the "AmEventsSubscData" data type specific per event subscription information, if applicable, and as described in clause 4.2.2.3.

NOTE: The NF service consumer can use this service operation to subscribe/unsubscribe to events that matched based on the provided requested policy related to the AM context (e.g. SAC_CH event, which is matched based on the requested service area coverage). In these cases, to avoid the PCF keeping stale subscription information, the NF service consumer needs to ensure that the concerned requested policy exists together with the event subscription, i.e. the event subscription is removed when the related policy is removed.

Upon the reception of the HTTP PUT request from the NF service consumer, the PCF shall decide whether the received HTTP PUT request is accepted.

If the HTTP PUT request from the NF service consumer is not accepted, the PCF shall indicate in the response to HTTP PUT request the cause for the rejection as specified in clause 5.7.

If the PCF determines the received HTTP PUT request needs to be redirected, the PCF shall send an HTTP redirect response as specified in clause 6.10.9 of 3GPP TS 29.500 [4].

If the PCF accepted the HTTP PUT request to create a subscription to events, the PCF shall create the "AM Policy Events Subscription" sub-resource and shall send the HTTP response message to the NF service consumer as shown in figure 4.2.5.2-1, step 2. The PCF shall include in the "201 Created" response:

– a Location header field that shall contain the URI of the created "AM Policy Events Subscription" sub-resource i.e. "{apiRoot}/npcf-am-policyauthorization/<apiVersion>/app-am-contexts/{appAmContextId}/events-subscription"; and

– a response body with the "AmEventsSubscRespData" data type, which:

a) shall contain the created "AM Policy Events Subscription" sub-resource encoded in the attributes of the "AmEventsSubscData" data type; and

b) if the NF service consumer requested the immediate reporting and the current value is available, may contain the corresponding event(s) notification by encoding event identifier within the "repEvents" the attribute and the applicable event(s) information as specified within the "AmEventsNotification" data type.

If the PCF accepted the HTTP PUT request to modify the events subscription, the PCF shall modify the "AM Policy Events Subscription" sub-resource and shall send to the NF service consumer:

– the HTTP "204 No Content" response (as shown in figure 4.2.5.2-2, step 2a); or

– the HTTP "200 OK" response (as shown in figure 4.2.5.2-2, step 2b) including in the "AmEventsSubscRespData" data type:

a) the updated representation of the "AM Policy Events Subscription" sub-resource encoded within the attributes of the "AmEventsSubscData" data type; and

b) if one or more of the updated subscribed events are already met in the PCF, the notification of these events by including the event identifier within the "repEvents" attribute and the applicable event(s) information as specified within the "AmEventsNotification" data type.

When the "monDur" attribute is included in the response, it represents a server selected expiry time that is equal or less than a possible expiry time in the request.

4.2.5.3 Subscription to events without an existing AF application AM context

This procedure is used by an NF service consumer (e.g. 5G DDNMF) to request the creation of a subscription to event(s) in the PCF when no "Individual application AM context" exists, and the NF service consumer does not provide Access and Mobility related service information, i.e., does not create an AF application AM context.

Figure 4.2.5.3-1 illustrates the subscription to event(s) without an existing AF application AM context.

Figure 4.2.5.3-1: Subscription to events without an existing AF application AM context

When an NF service consumer (e.g. 5G DDNMF) decides to create a subscription to one or more event(s), and the NF service consumer is not providing Access and Mobility related service information and the "Individual application AM context" resource does not exist, the NF service consumer shall invoke the Npcf_AMPolicyAuthorization_Subscribe service operation to create an "Individual application AM context" resource and the corresponding "AM Policy Events Subscription" sub-resource by sending an HTTP POST request to the resource URI representing the "Application AM contexts" collection resource of the PCF, as shown in figure 4.2.5.3-1, step 1.

The NF service consumer shall include in the AppAmContextData data type in the payload body of the HTTP POST request a partial representation of the "Individual Application AM Context" resource, which shall include:

– the notification URI where the PCF shall request the termination of the application AM context to the NF service consumer, encoded as "termNotifUri" attribute;

– the SUPI encoded as "supi" attribute; and

– the "evSubsc" attribute to subscribe to notifications of access and mobility policy changes events. The NF service consumer shall include within the associated AmEventsSubscData data type:

a. the notification URI where the NF service consumer wants to receive the event notifications, encoded as "eventNotifUri" attribute; and

b. the event(s) to subscribe to within the "events" attribute. For each subscribed event, the AmEventData data type shall include the event identifier in the "event" attribute and may include the description of the event reporting mode as specified in clause 4.2.5.2.

The event(s) subscription data is provisioned in the "AM Policy Events Subscription" sub-resource.

Otherwise, the PCF shall perform the association of the AF request to one and only one AM policy association or UE policy association. If the PCF fails in executing the binding with the AM policy association or UE policy association, the PCF shall reject the HTTP POST request with an HTTP "500 Internal Server Error" response and may include the "cause" attribute set to "POLICY_ASSOCIATION_NOT_AVAILABLE".

NOTE 1: In this release of the specification whether the AF request is associated to an AM policy association or to a UE policy association is determined per specific event, e.g., a subscription to PDUID changes implies the binding to a UE policy association.

If the PCF created an "Individual Application AM Context" resource and the corresponding "AM Policy Events Subscription" sub-resource, the PCF shall send to the NF service consumer a "201 Created" response to the HTTP POST request, as shown in figure 4.2.5.3-1, step 2. The PCF shall include in the "201 Created" response:

– a Location header field; and

– an AppAmContextRespData data type in the payload body.

The Location header field shall contain the URI of the created "AM Policy Events Subscription" sub-resource, i.e., "{apiRoot}/npcf-am-policyauthorization/<apiVersion>/app-am-contexts/{appAmContextId}/events-subscription".

The AppAmContextRespData data type payload body shall contain:

– the representation of the created "Individual application AM context" resource within the AppAmContextData data type, which shall also include the "AM Policy Events Subscription" sub-resource representation within the "evSubsc" attribute; and

– when the PCF determines that the subscribed event(s) is already met and/or the NF service consumer requested immediate reporting and the current value is available, the AppAmContextRespData data type shall include the corresponding event(s) notification within the "repEvents" attribute of the AmEventsNotification data type.

NOTE 2: The created "Individual application AM context" resource does not include Access and Mobility related service information, only includes the information supplied by the NF service consumer to perform the association to the concerned AM policy association or UE policy association, i.e., the "supi" attribute, the SBI handling specific properties, i.e. the "suppFeat" attribute and the "termNotifUri" attribute, together with the "evSubsc" attribute.

4.2.5.4 Subscription to PDUID changes

This procedure is used by a NF service consumer to request the PCF to subscribe to notifications of PDUID change event.

The NF service consumer requests the subscription to notifications of PDUID change without providing (Access and Mobility or 5G ProSe) service information at initial subscription to event(s), using the HTTP POST request message as described in clause 4.2.5.3.

The NF service consumer shall include within the "events" array attribute of the "evSubsc" attribute of the AppAmContextData data type:

– an event with the "event" attribute set to "PDUID_CH"; and

– to retrieve the current value of the PCF allocated PDUID for the UE, the request for immediate reporting by setting the "immRep" attribute to true.

The PCF shall perform the association of the AF request to the UE policy association and shall retrieve the internally stored PDUID value allocated to the UE for the UE 5G ProSe Policy.

Upon success, the PCF creates an "Individual Application AM Context" resource and the corresponding "AM Policy Events Subscription" sub-resource. The PCF shall then send a "201 Created" response to the HTTP POST request received from the NF service consumer, as described in clause 4.2.5.3, including the retrieved PDUID value within the AmEventsNotification data type as described in clause 4.2.7.5.

4.2.6 Npcf_AMPolicyAuthorization_Unsubscribe service operation

4.2.6.1 General

The Npcf_AMPolicyAuthorization_Unsubscribe service operation enables an NF service consumer to remove an existing subscription to event(s) for an existing AF application AM context. The Npcf_AMPolicyAuthorization_Unsubscribe service operation also enables an NF service consumers to remove an existing subscription to event(s) without an existing AF application AM context.

Such subscription to events shall be removed:

– by invoking the Npcf_AMPolicyAuthorization_Unsubscribe service operation for an existing AF application AM context, as described in clause 4.2.6.2; or

– within the AF application AM context modification procedure by invoking the Npcf_AMPolicyAuthorization_Update service operation, as described in clause 4.2.3; or

– within the AF application AM context termination procedure by invoking the Npcf_AMPolicyAuthorization_Delete service operation, as described in clause 4.2.4.

– by invoking the Npcf_AMPolicyAuthorization_Unsubscribe service operation when there is no existing Individual application AM context, as described in clause 4.2.6.3.

The following procedures using the Npcf_AMPolicyAuthorization_Unsubscribe service operation are supported:

– Unsubscription to events, Access and Mobility related service information exists.

– Unsubscription to events, Access and Mobility related service information does not exist.

4.2.6.2 Unsubscription to events, Access and Mobility related service information exists

This procedure is used to unsubscribe to all subscribed events when the NF service consumer previously provided access and mobility related service information for the existing AF application AM context, as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14]. As result of this procedure, the "AM Policy Events Subscription" sub-resource is removed but the "Individual application AM context" remains with the access and mobility related service information.

Figure 4.2.6.2-1 illustrates the procedure to unsubscribe from AM Policy Authorization event(s) using the HTTP DELETE method.

Figure 4.2.6.2-1: Removal of events subscription information using HTTP DELETE

When the NF service consumer decides to unsubscribe to all subscribed event(s) for an existing AF application AM context, and the NF service consumer previously provided access and mobility service information to the PCF, the NF service consumer shall invoke the Npcf_AMPolicyAuthorization_Unsubscribe service operation by sending an HTTP DELETE request message to the resource URI representing the concerned "AM Policy Events Subscription" sub-resource in the PCF, as shown in figure 4.2.6.2-1, step 1.

Upon the reception of the HTTP DELETE request message from the NF service consumer, the PCF shall decide whether the received HTTP request message is accepted.

If the HTTP DELETE request message from the NF service consumer is accepted, the PCF shall delete the "AM Policy Events Subscription" sub-resource and shall send to the NF service consumer a HTTP "204 No Content" response message.

If the HTTP DELETE request message from the NF service consumer is rejected, the PCF shall indicate in the HTTP response message the cause for the rejection as specified in clause 5.7.

If the PCF determines the received HTTP DELETE request needs to be redirected, the PCF shall send an HTTP redirect response as specified in clause 6.10.9 of 3GPP TS 29.500 [4].

4.2.6.3 Unsubscription to events, Access and Mobility related service information does not exist

This procedure is used by the NF service consumer to unsubscribe to all subscribed event(s) when the AF application AM context does not contain access and mobility related service information, i.e. only contains the "supi" attribute, the SBI handling specific properties, i.e. the "suppFeat" attribute and the "termNotifUri", together with the subscription information encoded in the "evSubsc" attribute. As a result of this procedure, the "AM Policy Events Subscription" sub-resource and the parent "Individual application AM context" resource are both removed.

The procedure to unsubscribe from AM Policy Authorization events when the AF application AM context does not contain access and mobility related service information is the same as the procedure to delete the AF application AM context defined in clause 4.2.4.2.

4.2.7 Npcf_AMPolicyAuthorization_Notify service operation

4.2.7.1 General

The Npcf_AMPolicyAuthorization_Notify service operation enables to notify to the NF service consumers that the previously subscribed event for the existing AF application AM context occurred or that the AF application AM context is no longer valid.

The following procedures using the Npcf_AMPolicyAuthorization_Notify service operation are supported:

– Notification about AF application AM context event.

– Notification about AF application AM context termination.

– Notification about service area coverage change outcome.

– Notification about PDUID changes.

4.2.7.2 Notification about AF application AM context event

This procedure is invoked by the PCF to notify the NF service consumer when a certain, previously subscribed, AF application AM context event occurs, as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.7.2-1 illustrates the notification about AF application AM context event.

Figure 4.2.7.2-1: Notification about AF application AM context event

When the PCF determines that the event for the existing AF application AM context, to which the NF service consumer has subscribed to, occurred, the PCF shall invoke the Npcf_AMPolicyAuthorization_Notify service operation by sending the HTTP POST request (as shown in figure 4.2.7.2-1, step 1) to the NF service consumer using the callback URI received in the subscription creation (or modification), as specified in clauses 4.2.2.2, 4.2.3.2 and 4.2.5.2. The PCF shall provide in the body of the HTTP POST request the "AmEventsNotification" data type including:

– the AM Policy Events Subscription resource identifier related with the notification in the "appAmContextId" attribute; and

– the list of the reported events in the "repEvents" attribute. For each reported event, the "AmEventNotification" data type may include additional event information.

The notification of other specific events using the Npcf_AMPolicyAuthorization_Notify request is described in the related clauses.

Upon the reception of the HTTP POST request from the PCF indicating that the subscribed event occurred, the NF service consumer shall acknowledge that request by sending an HTTP response message with the corresponding status code.

If the HTTP POST request from the PCF is not accepted, the NF service consumer shall indicate in the response to HTTP POST request the cause for the rejection as specified in clause 5.7.

If the HTTP POST request from the PCF is accepted, the NF service consumer shall acknowledge the receipt of the event notification with a "204 No Content" response to HTTP POST request, as shown in figure 4.2.7.2-1, step 2.

If the NF service consumer determines the received HTTP POST request needs to be redirected, the NF service consumer shall send an HTTP redirect response as specified in clause 6.10.9 of 3GPP TS 29.500 [4].

4.2.7.3 Notification about AF application AM context termination

This procedure is invoked by the PCF to notify the NF service consumer that the AF application AM context is no longer valid, as defined in 3GPP TS 23.501 [2], 3GPP TS 23.502 [3] and 3GPP TS 23.503 [14].

Figure 4.2.7.3-1 illustrates the notification about AF application AM context termination.

Figure 4.2.7.3-1: Notification about AF application AM context termination

When the PCF determines that the AF application AM context is no longer valid, the PCF shall invoke the Npcf_AMPolicyAuthorization_Notify service operation by sending the HTTP POST request (as shown in figure 4.2.7.3-1, step 1) using the callback URI received in the "Individual application AM context" resource creation, as specified in clause 4.2.2.2. The PCF shall provide in the body of the HTTP POST request the "AmTerminationInfo" data type including:

– the Individual application AM context resource identifier related to the termination notification within the "appAmContextId" attribute; and

– the AF application AM context termination cause within the "termCause" attribute encoded using of the "AmTerminationCause" data type, indicating the termination cause.

Upon the reception of the HTTP POST request from the PCF requesting the AF application AM context termination, the NF service consumer shall acknowledge that request by sending an HTTP response message with the corresponding status code.

If the HTTP POST request from the PCF is not accepted, the NF service consumer shall indicate in the response to HTTP POST request the cause for the rejection as specified in clause 5.7.

If the HTTP POST request from the PCF is accepted, the NF service consumer shall acknowledge the receipt of the AF application AM context termination request with a "204 No Content" response (as shown in figure 4.2.7.3-1, step 2) and shall invoke the Npcf_AMPolicyAuthorization_Delete service operation to the PCF as described in clause 4.2.4.

4.2.7.4 Notification about service area coverage change outcome

When the PCF becomes aware that the request received from the NF service consumer to change the service area coverage is performed, it shall inform the NF service consumer accordingly if the NF service consumer has previously subscribed to the "SAC_CH" event as described in clauses 4.2.2.3 and 4.2.3.3.

The PCF shall notify the NF service consumer by including the AmEventsNotification data type in the body of the HTTP POST request as described in clause 4.2.7.2. The PCF shall include within an entry of the "repEvents" attribute:

– the "event" attribute set to "SAC_CH" in the "event" attribute;

– the applied service area coverage (same or different service area coverage from the service area coverage provided by the NF service consumer) in the "appliedCov" attribute.

When the result of the execution of the request of service area coverage is that the service is allowed in one or more of the requested Tracking Areas in the serving network where the UE is camping, the "appliedCov" attribute shall encode within the "tacList" attribute the list of NF consumer provided Tracking Area codes where the requested service shall be allowed and within the "servingNetwork" attribute the serving network where the UE is camping.

When the result of the execution of the request of service area coverage change is that the service is restricted in the whole NF requested service area coverage, the "appliedCov" attribute shall encode an empty array within the "tacList" attribute.

NOTE: The actual service area coverage for the UE might be larger than the one reported within "appliedCov" attribute. The "appliedCov" attribute provides to the NF consumer feedback about where the service is allowed in relation to the NF consumer provided service area coverage.

When the NF service consumer indicated that the notification method is "ON_EVENT_DETECTION" (or omitted it) during the subscription, the subscription to this event is kept in the PCF until the NF service consumer terminates the subscription as described in clause 4.2.3.2 or 4.2.6.2. The NF service consumer shall be notified of subsequent service area coverage changes (i.e., changes in the applied service area coverage, which may indicate e.g. no service area coverage is allowed) as specified in bullets above without requiring a new subscription, both, when the service area coverage change is triggered by the NF service consumer and/or triggered by other events (e.g. based on PCF internal policies and/or changes in the subscribed service area restrictions), and as long as the requested service area coverage requirements exist (e.g, they have not expired).

Upon receipt of the HTTP POST request from the PCF, the NF service consumer shall acknowledge the request by sending a "204 No Content" response as described in clause 4.2.7.2.

4.2.7.5 Notification about PDUID changes

When the PCF allocates a new PDUID (ProSe Discovery UE ID) for the UE 5G ProSe Policy of a SUPI, the PCF shall inform the NF service consumer that previously subscribed as described in clause 4.2.5.4.

The PCF shall notify the NF service consumer by including the AmEventsNotification data type in the body of the HTTP POST request as described in clause 4.2.7.2, which shall include within an entry of the "repEvents" attribute:

– the "PDUID_CH" event within the "event" attribute; and

– the "pduidInfo" attribute, with the allocated PDUID within the "pduid" attribute and its validity timer within the "expiry" attribute.

When the NF service consumer receives the notification in the HTTP POST request, it shall acknowledge the request by sending a "204 No Content" response to the PCF as specified in clause 4.2.7.2.