AM Policy Association (TS 29.507 §4.2.2 — NpcfAMPolicyControl)

Mirrored documentation

Mirrored read-only from claudia-5gc @ v2.3.1. Edit upstream, not here.

Purpose

At UE registration AMF creates an AM Policy Association with PCF (N15 interface, npcf-ampolicycontrol). PCF returns the RFSP index (Radio Frequency Selection Priority), service area restrictions, and UE-AMBR override if configured. The AMF stores the polAssoId to release it at deregistration and to trigger updates when the UE moves.

This procedure is distinct from Npcf_UEPolicyControl (URSP delivery, TS 29.525):

• npcf-ampolicycontrol (TS 29.507) → AM policies: RFSP, service area, UE-AMBR
• npcf-ue-policy-control (TS 29.525) → UE policies: URSP rules

Specifications

Topic	Reference
Architecture	TS 23.501 §5.6.2
Procedure flow	TS 23.502 §4.2.2.2.2 step 14c
Stage 3	TS 29.507 §4.2.2
Data model	TS 29.507 §6.1.1.2 (PolicyAssociationRequest / PolicyAssociation)

Sequence Diagram

sequenceDiagram
    participant UE
    participant AMF
    participant PCF
    participant UDM

    AMF->>UDM: Nudm_SDM_Get AM data (step 16)
    UDM-->>AMF: AMSubscriptionData (AllowedNSSAI, SubscribedAMBR)

    Note over AMF,PCF: Step 14c — AM Policy Association
    AMF->>PCF: POST /npcf-ampolicycontrol/v1/policies\n{supi, accessType="3GPP_ACCESS", plmnId}
    PCF-->>AMF: 201 Created\nLocation: /npcf-ampolicycontrol/v1/policies/{polAssoId}\n{polAssoId, rfsp=1, triggers=[]}

    AMF->>AMF: Store polAssoId in UEContext
    AMF-->>UE: Registration Accept (step 20)

Information Elements

PolicyAssociationRequest (AMF → PCF, POST body)

IE	Type	M/O	Description
supi	string	M	UE’s SUPI
pei	string	O	UE permanent equipment identifier
accessType	enum	M	3GPP_ACCESS or NON_3GPP_ACCESS
plmnId	object	O	PLMN id of serving network (mcc, mnc)
notificationUri	URI	O	Callback for policy update notifications

PolicyAssociation (PCF → AMF, response body)

IE	Type	Description
polAssoId	string	Assigned association ID (ULID)
rfsp	integer	Radio Frequency Selection Priority (1-256); optional
triggers	array	Policy control request triggers; empty if none
servAreaRes	object	Service area restrictions; omitted if unrestricted
ueAmbr	object	UE-AMBR override; omitted if no override

Error Cases

Condition	HTTP Status	Cause
Missing supi	400	MANDATORY_IE_MISSING
Missing accessType	400	MANDATORY_IE_MISSING
Unknown polAssoId in DELETE	404	POLICY_ASSOCIATION_NOT_FOUND

Implementation Notes

• Association stored in PCF’s in-memory amPolicies map (keyed by polAssoId).
• polAssoId = ULID.
• Default response: rfsp=1, empty triggers, no servAreaRes (unrestricted).
• DELETE /npcf-ampolicycontrol/v1/policies/{polAssoId} returns 204.
• AMF calls this non-fatally in Phase3 (step 14c); failure does not block Registration Accept.
• AMF stores AMPolicyAssocID in UEContext and releases it on deregistration.