UDR Policy Data Resource (TS 29.504 §5.2.13 / TS 29.519 — NudrDataRepository)

Mirrored documentation

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

Purpose

The UDR is the data repository for policy data (TS 29.519), retrieved and provisioned by the PCF over the N36 reference point using Nudr_DataRepository (TS 29.504). Today the UDR exposes only the UE Policy Set (URSP) resource; the SM Policy Data resource is missing, so the PCF cannot source per-subscriber/per-DNN SM policy (authorized 5QI / ARP / Session-AMBR) from the repository — its QoS overrides live only in PCF process memory and are lost on restart.

This task makes SM Policy Data a first-class Nudr_DR resource (GET/PUT/PATCH), adds PATCH to the existing UE Policy Set resource for parity, and routes the PCF reads and writes of SM policy data through Nudr_DR so the policy decision is repository-backed and survives a PCF restart.

Resource-path note. TS 29.519 nests policy data under /policy-data/ues/{ueId}/sm-data. The existing UDR follows a simplified house style that places the SUPI directly after policy-data (/nudr-dr/v2/policy-data/{supi}/ue-policy-set, already in use by the URSP resource). The SM Policy Data resource added here keeps that house style: /nudr-dr/v2/policy-data/{supi}/sm-data. The backlog (UDR-001) refers to it loosely as “sm-policy”; the spec resource name is SmPolicyData.

Specifications

Topic	Reference
Nudr_DataRepository (Stage 3)	TS 29.504 §5.2.13 (policy data)
Policy data model — SmPolicyData	TS 29.519 §5.6.2.4
Policy data model — SmPolicySnssaiData	TS 29.519 §5.6.2.5
Policy data model — SmPolicyDnnData	TS 29.519 §5.6.2.6
UE Policy Set	TS 29.519 §5.7, TS 29.525
PCF SM Policy decision	TS 29.512 §5.2.2.2, TS 23.503 §6.2.1

Sequence Diagram

sequenceDiagram
    participant MGMT as MCP / Portal
    participant PCF
    participant UDR
    participant SMF

    Note over MGMT,UDR: Provisioning — PCF writes SM policy data through Nudr_DR
    MGMT->>PCF: PUT /pcf-internal/.../sm-policy-override {5qi, dnn, snssai?, ambr}
    PCF->>UDR: PUT /nudr-dr/v2/policy-data/{supi}/sm-data\n{smPolicySnssaiData:{...}}
    UDR-->>PCF: 204 No Content
    PCF-->>MGMT: 200 OK

    Note over SMF,UDR: SM Policy decision — PCF reads SM policy data from Nudr_DR
    SMF->>PCF: POST /npcf-smpolicycontrol/v1/sm-policies {supi, dnn, snssai, subsDefQos}
    PCF->>UDR: GET /nudr-dr/v2/policy-data/{supi}/sm-data
    alt SM policy data exists for (snssai, dnn)
        UDR-->>PCF: 200 SmPolicyData
        PCF->>PCF: authorized 5QI/ARP/AMBR ← UDR (qos_source=UDR_POLICY_DATA)
    else not provisioned
        UDR-->>PCF: 404 (fail-open → subsDefQos / operator default)
    end
    PCF-->>SMF: 201 Created SmPolicyDecision

Resources & Operations

Method	Route	Body / Response	Spec
GET	/nudr-dr/v2/policy-data/{supi}/sm-data	→ SmPolicyData (200) / 404	TS 29.519 §5.6.2.4
PUT	/nudr-dr/v2/policy-data/{supi}/sm-data	SmPolicyData → 204	TS 29.504 §5.2.13
PATCH	/nudr-dr/v2/policy-data/{supi}/sm-data	SmPolicyData (merge) → 204	TS 29.504 §5.2.13
GET	/nudr-dr/v2/policy-data/{supi}/ue-policy-set	→ PolicySubscription (200) / 404	existing
PUT	/nudr-dr/v2/policy-data/{supi}/ue-policy-set	PolicySubscription → 204	existing
PATCH	/nudr-dr/v2/policy-data/{supi}/ue-policy-set	partial PolicySubscription → 204	TS 29.504 §5.2.13
DELETE	/nudr-dr/v2/policy-data/{supi}/ue-policy-set	→ 204	existing

Information Elements — SmPolicyData (TS 29.519 §5.6.2.4)

IE	Type	M/O	Description
smPolicySnssaiData	map[snssaiKey → SmPolicySnssaiData]	M	Per-S-NSSAI policy data. Key = "sst" or "sst-sd" (e.g. "1-000001")

SmPolicySnssaiData (§5.6.2.5)

IE	Type	M/O	Description
snssai	Snssai	M	The S-NSSAI this entry applies to (sst, optional sd)
smPolicyDnnData	map[dnn → SmPolicyDnnData]	O	Per-DNN policy data

SmPolicyDnnData (§5.6.2.6 — pragmatic subset)

IE	Type	M/O	Description
dnn	string	M	Data Network Name
5qi	int	O	Authorized default 5QI for the DNN
arpPriorityLevel	int	O	Authorized ARP priority level (1–15)
ambrUplink	string	O	Authorized Session-AMBR uplink (e.g. "100 Mbps")
ambrDownlink	string	O	Authorized Session-AMBR downlink

Modelling note. TS 29.519 SmPolicyDnnData carries many fields (gbrUl/gbrDl, adcSupport, subscCats, online/offline charging, …). This implementation persists the subset the PCF uses to make the SM policy QoS decision (authorized 5QI / ARP / Session-AMBR per DNN). The resource shape (smPolicySnssaiData → smPolicyDnnData) follows the spec; unused fields are omitted.

PCF integration (criterion 2 — “PCF reads/writes policy data through Nudr_DR”)

• Write — handleSetQoSOverride (PCF internal mgmt API) write-throughs the override to UDR so a configured QoS policy is persisted in the repository (survives a PCF restart). The write is read-modify-write: the PCF reads the current SmPolicyData, replaces only its own bucket (udrSmPolicyBucketKey="0") with the rebuilt overrides — or removes that bucket on handleDeleteQoSOverride — and writes the result back, so directly-provisioned per-S-NSSAI slices are preserved (the PCF does not own the whole document). Best-effort: a UDR read/write failure is logged, non-fatal (in-memory override still applied).
• Read — handleCreateSmPolicy queries GetSmPolicyData(supi) when no in-memory override matches, resolving the authorized QoS for the session’s (snssai, dnn). This is a new precedence tier reported as x5gcQosSource = UDR_POLICY_DATA, sitting above the UDM subscription default (subsDefQos) and operator config.

QoS decision precedence (PCF SmPolicyControl_Create, highest first)

1. DNN-scoped in-memory override (supi|dnn)
2. Subscriber-wide in-memory override (supi)
3. UDR SM Policy Data ((snssai, dnn) from Nudr_DR) ← new
4. Subscribed default QoS from SMF (subsDefQos — UDM sm-data)
5. Operator config defaults

Because the write path keeps the in-memory override (tier 1/2) and also persists to UDR (tier 3), the live decision is byte-identical to before for an active PCF; after a restart, tier 3 restores the same decision from the repository. Zero regression when UDR is absent: the PCF read is fail-open (a nil client, a 404, or any error falls through to subsDefQos/defaults).

Error Cases

Condition	HTTP Status	Cause
GET sm-data, none provisioned	404	DATA_NOT_FOUND
Malformed PUT/PATCH body	400	MANDATORY_IE_INCORRECT
Store backend failure	500	SYSTEM_FAILURE
PATCH ue-policy-set, subscriber has no policy	404	DATA_NOT_FOUND

Implementation Notes

• UDR: SmPolicyData/SmPolicySnssaiData/SmPolicyDnnData added to shared/types (re-exported by the UDR store, mirroring PolicySubscription). New store methods GetSmPolicyData, PutSmPolicyData, PatchSmPolicyData on the Store interface, implemented for both InMemory and Postgres (new subscription_sm_policy JSONB table, migration 004_sm_policy_data.sql).
• PATCH merges at the smPolicySnssaiData map granularity (provided S-NSSAI entries replace the existing entry for that key; absent keys are preserved) — a 404 if no row exists yet.
• PCF: UDRClient gains GetSmPolicyData + PutSmPolicyData; HTTPUDRClient implements them against the new routes. The SM policy create read and the override write-through are both guarded by s.udrClient != nil and are non-fatal.
• Validation: in-process (UDR store + handlers, PCF read/write precedence). No N1/N2/N4 path is touched — the live PDU-session decision is unchanged for the default 5qi=9 session.