URSP is pre-configured in the UE or provisioned to UE from PCF. The pre-configured policy is applied by the UE only when it has not received the same type of policy from the PCF.

• PCF selects the UE policy information applicable for each UE based on local configuration, and operator policies.

• PCF provides the UE policy information to the AMF through N15 or Namf interface and then from AMF to the UE through the N1 interface and AMF will not change the UE policy information provided by the PCF.

• PCF adds policy control trigger through Npcf_UEPolicyControl Create Response to AMF.

• The PCF is responsible for delivery of UE policy. If the PCF is notified about UE policy information delivery failure, then PCF will retry based on the configuration.

• If the UE has an URSP rule (except the URSP rule with the match all traffic descriptor) that matches the application as the UE shall perform the association of the application to the corresponding PDU session.

• If no URSP rule is applicable for the application, the UE shall perform the association of the application to a PDU session according to the applicable UE local configurations.

UE Policy Delivery

• PCF provides the UE policy information during UE Policy Association Establishment and UE Policy Association Modification procedures.

• The PCF includes the UE policy information delivered to the UE into a Policy Section identified by a Policy Section Identifier (PSI).

• The PCF may divide the UE policy information into different Policy Sections, each one identified by a PSI. Each policy section provides a list of self-contained UE policy information to the UE, through AMF. The PCF ensures that a policy section is under a predefined size limit, known by the PCF.

• The size limit is configured in the PCF. The PLMN ID is provided to the UE together with UE policy information and it is used to indicate which PLMN a policy section list belongs to.

• If the UE has no policy sections with the same PSI, the UE stores the policy section.

• If the UE has an existing policy section with the same PSI, the UE replaces the stored policy section with the received information.

• The UE removes the stored policy section if the received information contains only the PSI.

• The UE keeps the received UE policies stored even when registering in another PLMN.

• The UE provides the list of stored PSIs (Policy Section Identifier) which identify the policy sections associated to the home PLMN that are currently stored in the UE.

• The UE may trigger an initial registration with the list of stored PSIs to request a synchronization for example if the UE powers up without USIM being changed.

• If USIM is changed, the UE does not provide any PSI. If no policies are stored in the UE for the home PLMN, the UE does not provide any PSI associated to the home PLMN.

• PCF subscribes to the AMF to be notified about the UE response to an update of UE policy information.

• PCF invokes Namf_Communication_N1N2MessageTransfer service operation then AMF shall transfer transparently the UE Policy to UE.

• After the successful N1Message Notification from AMF, UE Policy gets installed in the UE. So PCF will send the UDR update message with the installed UE Policy details.

• When UE is not reachable AMF reports to the PCF that the UE Policy could not be delivered to the UE using Namf_Communication_N1N2TransferFailureNotification.

Principles of PTI Handling For UE Policy Delivery Service Procedures

When the PCF or the UE initiates a procedure, it shall include a valid PTI value in the message header of the command message or the request message.

When the PCF initiates a transaction related procedure, it shall include a valid PTI value in the message header of the command message.

If a response message is sent as a result of a received command or request message, the UE or the PCF shall include in the response message the PTI value received within the received command or request message.

If a command message is sent as a result of a received request message, the PCF shall include in the command message the PTI value received with the request message.

To initiate the network-requested UE policy management procedure, the PCF shall:

• Allocate a PTI value currently not used and set the PTI IE to the allocated PTI value.

• Encode the information about the UE policy sections to be added, modified, or deleted in a UE policy section management list IE as specified in subclause D.6.2 and include it in a MANAGE UE POLICY COMMAND message.

• Send the MANAGE UE POLICY COMMAND message to the UE via the AMF .

• Start the timer T3501.

Note	The PCF starts a different timer T3501 for each allocated PTI value.

UE Policy Delivery Service Message Type

The purpose of the UE policy section management list information element is to transfer from the PCF to the UE a list of instructions to be performed at the UE for management of UE policy section stored at the UE.

The UE policy section management list information element has a minimum length of 12 octets and a maximum length of 65534 octets.

The value part of the UE policy section management list information element consists of one or several UE policy section management sub lists.

UE Policy Section Management Sublist

Following are the details of UE policy section management sub list:

• Length of UE policy section management sub list (octets d to d+1). This field contains the binary encoding of the length of the UE policy section management sub list in units of octets.

• Mobile country code (MCC) from octet d+2, and bits 4 to 1 of octet d+3.

• Mobile network code (MNC) from bits 8 to 5 of octet d+3, and octet d+4 .

• The coding of this field is the responsibility of each administration, but BCD coding shall be used. The MNC shall consist of 2 or 3 digits. If a network operator decides to use only two digits in the MNC, MNC digit 3 shall be coded as 1111.

The UE policy section management sub list contents consist of one or several instructions.

Instructions:

• Instruction contents length (octets d+5 to d+6) This field contains the binary encoding of the instruction contents length in units of octets.

• UPSC (octets d+7 to d+8) This field contains the binary encoding of the UPSC. The value of the UPSC is set by the PCF.

• UE policy section contents (octets d+9 to k)

The UE policy section contents consist of one or several UE policy parts.

UE policy part contents length (octets q to q+1) . This field contains the binary encoding of the UE policy part contents length in units of octets.

UE policy part type (bits 4 to 1 of octet q+2)

Bits

0 0 0 1 URSP

Bits 8 to 5 of octet q+2 are spare and shall be coded as zero.

UE policy part contents

This field contains a UE policy part encoded as specified in 3GPP TS 24.526 [19] for the UE policy part type field set to URSP or ANDSP and encoded as specified in 3GPP TS 24.588 [19C] for the UE policy part type field set to V2XP (V2X Policy).

UE Policy Association Management Service

• Npcf_UEPolicyControl Create Request - This message is for UE Policy Establishment.

• Npcf_UEPolicyControl Delete Request - Provides means to delete UE Policy Association.

• Namf_ Communication_N1N2Message N1N2MessageTransfer (UE Specific) - This service operation is used by PCF to transfer N1 and/or N2 information to the UE and/or 5G-AN through the AMF.

• Namf_ Communication_N1N2Message N1N2MessageSubscribe (UE Specific) - This message is used by PCF to subscribe to the AMF for notifying N1 messages of a specific type or N2 information of a specific type.

• Namf_ Communication_ N1MessageNotify - This N1MessageNotify service operation is invoked by the AMF, towards the PCF which subscribed to be notified with UPDP messages received from the UE.

• Namf_ Communication_N1N2MessageUnSubscribe - This service operation is used by PCF to unsubscribe to the AMF to stop notifying N1 messages of a specific type .

• Namf_ Communication_N1N2Message N1N2TransferFailureNotification (UE Specific) - This notification to inform PCF that an earlier Namf_Communication_N1N2Message Transfer failed, since AMF failed to deliver the N1 message to the UE as the UE failed to respond to paging.

UDR Query APIs

Following are the APIs for UDR query UEPolicySet:

• GET - Retriver the policy data set for a subscriber.

• PATCH - Modify the policy data set for a subscriber.

UE Policy Association Creation

UE Policy Association create request will be triggered by AMF in following scenarios:

• UE initial registration with the network.

• UE registration with 5GS when the UE moves from EPS to 5GS and there is no existing UE Policy Association between AMF and PCF for this UE.

The AMF creates the UE policy association with the PCF when a UE policy is received from the UE.

The AMF sends a Npcf_UEPolicyControl Create Request with SUPI, may include Access Type and RAT, PEI (Permanent Equipment Identifier), ULI, UE time zone, Serving Network (PLMN ID, or PLMN ID and NID), the Internal-Group-ID-list and UE Policy Container (the list of stored PSIs, operating system identifier).

PCF gets policy subscription related information and the latest list of PSIs from the UDR using Nudr_DM_Query service operation (SUPI, Policy Data, UE context policy control data, Policy Set Entry)

Then PCF sends a Npcf_UEPolicyControl Create Response to the AMF. The PCF relays the Policy Control Request Trigger parameters in the Npcf_UEPolicyControl Create Response.

To establish a UE policy association with the PCF, AMF request with {apiRoot}/npcf-ue-policy-control/v1/policies as Resource URI and the PolicyAssociationRequest data structure as request body shall include the following attributes:

• Notification URI as notificationUri attribute

• SUPI as supi attribute

• Features supported by the NF service consumer as suppFeat attribute

Following are the optional attributes:

• GPSI as gpsi attribute.

• Access type as accessType attribute

• Permanent Equipment Identifier (PEI) as pei attribute

• User Location Information as userLoc attribute

• UE Time Zone as timeZone attribute

• Identifier of the serving network (the PLMN Identifier or the SNPN Identifier), as servingPlmn attribute

• RAT type as ratType attribute

{
  "notificationUri": "string",
  "altNotifIpv4Addrs": [
    "string"
  ],
  "altNotifIpv6Addrs": [
    "string"
  ],
  "altNotifFqdns": [
    "string"
  ],
  "supi": "string",
  "gpsi": "string",
  "accessType": "string",
  "pei": "string",
  "userLoc": "string",
  "timeZone": "string",
  "servingPlmn": "string",
  "ratType": "string" [
    "string"
  ],
  
  "suppFeat": "string"
}

Following is the response body:

• The negotiated supported features are encoded as a suppFeat attribute.

• The information provided by the NF service consumer when requesting the creation of this policy association encoded as a request attribute.

• Following Policy Control Request Trigger are encoded as the triggersattribute:

  • Location change (tracking area)

  • Change of UE presence in PRA

  • Change of PLMN, if the PlmnChange feature is supported.

  • Change of UE connectivity state, if the ConnectivityStateChange feature is supported.

Note	Supports only the PlmnChange and Connectivity Changetwo feature numbers.

UDR GET QUERY

As a part of UE policy association creation and modification request, PCF makes UDR GET request to get UDR profile for the subscriber on ue-policy-set URI.

The response for UDR Get request on UE Policy set has upsi list and urPolicySections, pei, osIds.

As a part of UE Policy Association create request, PCF subscribes to the UDR on any changes of UE Policy Set for the subscriber.

PCF requests notifications from the UDR on changes in the policy data subscription information, and in this case, the PCF shall invoke the Nudr_DataRepository_Subscribe service operation by sending an HTTP POST request to the PolicyDataSubscriptions resource (/policy-data/subs-to-notify/{subsId}).

N1 N2 Message Subscribe and Unsubscribe

To subscribe to notifications of N1 message for UE Policy Delivery Result, or subsequent UE policy requests, the PCF invokes Namf_Communication_N1N2MessageSubscribe service operation to the AMF by sending the HTTP POST method with the URI of the N1N2 Subscriptions Collection for Individual UE Contexts resource.

This subscribe request has ueContextId, n2NotifyCallBackUri and n1MessageClass (UPDP) attributes provided by the PCF.

UE Policy Association Termination

The following cases are considered for UE Policy Association Termination:

• UE Deregistration from the network.

• The mobility with change of AMF .

• 5GS to EPS mobility with N26 if the UE is not connected to the 5GC over a non-3GPP access in the same PLMN.

Ops Center Configuration

Following are the configuration details:

n1n2message.transfer.retry.interval.in.secs

After the N1 message failure notification, PCF will retry after the configured interval using the following configuration:

n1n2message.transfer.retry.times

The following configuration is to know the number of retry of the N1N2 message transfer after the failure or Un-acknowledged status from the AMF.

n1n2message.transfer.ack.timer.in.secs

Following are the call flows for UE registration and UE de-registration:

Following is the call flow for N1N2 transfer failure: