Policy &
Charging.
The module where the network becomes a business. The PCF and its three policy associations, URSP — the law book the network writes into your phone, the PCC rule’s six regions, tripwire triggers, spending limits, and the converged CHF: quotas, thresholds, CDRs and the graceful art of running out of credit — narrated and fully animated, with a cinematic camera.
Policy & Charging — rules like a lawyer, ledgers like an accountant
The player screen is a live animation stage with a cinematic camera — gauges fill, quotas drain and coins burst exactly as the narration reaches them. Karaoke subtitles in English, two subtitle modes, fullscreen.
Every information element in the module
Each policy and charging structure the video opens — its interface, direction, purpose and clause. Click any row to open its full breakdown. Filter to find any of them.
| Structure | Interface | Dir | What it does | Clause |
|---|
Policy & Charging, at protocol depth
Everything the video animates, as reference you can scan: the PCF’s three associations, the exact URSP structure, the PCC rule’s six regions, the session poster, every tripwire, and the quota machine. All spec-cited.
AM Policy — where may you roam
- AMF ⇄ PCF (N15) · Npcf_AMPolicyControl.
- Service area restrictions: allowed / not-allowed TAIs (+ max count).
- RFSP index steers frequency layers; UE-AMBR caps the device.
- UE enforces while IDLE · RAN/AMF while CONNECTED.
UE Policy — the phone’s law book
- PCF → AMF (N15) → UE (N1/NAS) · Npcf_UEPolicyControl.
- Carries URSP + ANDSP (+ V2XP, ProSeP, A2XP, RSLPP).
- Split into Policy Sections (PSI), each under the NAS size limit.
- The AMF shall NOT change it — a courier, not an editor.
SM Policy — lanes and money
- SMF ⇄ PCF (N7) · Npcf_SMPolicyControl.
- Unit of law: the PCC rule (Table 6.3.1).
- Plus the session poster: AMBR, thresholds, triggers (Table 6.4-1).
- Becomes PDR·QER·URR in the UPF, via N4.
Rule precedence
- Mandatory · every rule a different value.
- Evaluated strictly lowest-first.
Traffic descriptor — ALL must match
- Application descriptors (OSId + OSAppId).
- IP descriptors (dest IP · port · protocol) — never with Non-IP.
- Domain descriptors (FQDN / regex) · DNN.
- Connection Capabilities ("ims", "mms", "internet"…).
- Spec advice: at most two components.
Route Selection Descriptors — tried in order
- S-NSSAI(s) · DNN(s) — the RSD’s DNN replaces the app’s ask.
- SSC mode (3 ⇒ IP only) · PDU session type.
- Non-seamless offload (alone) · access-type preference.
- Validation: time window · location criteria.
Matching cascade: first rule whose descriptor fully matches → try its RSDs by precedence → reuse a matching PDU session or establish one → else next rule. Order of authority: URSP rule → UE Local Config → match-all rule.
1 · identity
- rule id · precedence · SDF template (filters or app-id)
2 · charging
- charging key = rating group · method (online/offline/neither) · blocking?
3 · policy
- gate · 5QI/ARP · 4 bitrates · QNC · reflective · alt-QoS · L4S
4 · reporting
- location · timezone · satellite id
5 · monitoring
- monitoring key · session-bucket exclusion
6 · steering
- DNAI(s) · per-DNAI policy · AF subscriptions
Life cycle (§6.3.2): activate → modify (dynamic only) → deactivate · one rule = one QoS flow · dynamic replaces predefined on identifier clash, wins precedence ties · deferred activation/deactivation only on the default-QoS-rule flow, never deferring QoS/filters.
| Attribute | What it does | Scope |
|---|---|---|
| Charging information | CHF address (+ instance/set ID) — where the money conversation happens | PDU session |
| Default charging method | for every rule that doesn’t state its own | PDU session |
| Authorized Session-AMBR | ceiling of all Non-GBR flows — enforced in the UPF via N4 | PDU session |
| Authorized default 5QI/ARP | quality of the default QoS flow | PDU session |
| Time Condition + Subsequent AMBR/5QI | up to 4 scheduled future changes — midnight, pre-ordered | PDU session |
| Revalidation time limit | SMF must re-request policy before the clock expires | PDU session |
| Monitoring key + Volume/Time threshold | the data-pack bucket: count silently, interrupt at threshold | Monitoring key |
| Monitoring time + Subsequent thresholds | re-arm the bucket at a set time | Monitoring key |
| Inactivity Detection Time | stop the usage clock when no packets flow | Monitoring key |
| PRA Identifier(s) | geofences the session should watch | PDU session |
Source: POLICY = 23.503 Table 6.1.3.5-1 (PCF arms the SMF) · CHARGING = 32.255 Table 5.2.1.4.1 (CHF arms the SMF). Immediate = report now · deferred = tell me with the next message.
| Trigger | Source | Level | Category | What fires it |
|---|
SDF starts
- online rule → need fuel
Request
- CDR-Req [Update] · Requested Unit
Grant
- granted units + thresholds + validity time
Threshold
- low-fuel lamp → re-request while flowing
Exhausted
- final grant carries finalUnitAction
Termination action
- allow · drop · redirect (top-up portal)
The pipeline
- SMF embeds the CTF → senses chargeable moments.
- Nchf/N40 → CHF (acts as CDF) → opens/updates/closes CDRs.
- CDRs → CGF (Ga if external) → files → Billing Domain (Bd).
- Charging Identifier: minted per session by the first SMF, survives handovers.
FBC vs QBC
- FBC — per rating group (+service id) — the default; the retail bill.
- QBC — per QoS flow — interconnect/wholesale, roaming charging profile.
- Home-routed: V-SMF→V-CHF and H-SMF→H-CHF — each counts at home.
- Both may run in the same charging session.
| Step | Actor | What happens |
|---|---|---|
| 9ch-a | SMF | creates the Charging Identifier · sends Charging Data Request [Initial] (start of PDU session) |
| 9ch-b | CHF | opens the CDR for this PDU session |
| 9ch-c | CHF | acknowledges with Charging Data Response [Initial] — may carry the first quota grants |
| 16ch-a..c | SMF⇄CHF | if “start of service data flow” needs quota: [Update] request → CDR update → grant (not for offline-only) |
| release 2ch | SMF⇄CHF | [Termination] with trigger “End of PDU session” — the CHF seals the CDR |
The rule to remember: policy and charging is one loop, not two features. The PCF writes the law — URSP into the phone, PCC rules into the SMF; tripwires report life back; the CHF counts money and its counters rewrite the law. Master the PCC rule’s six regions and the three charging messages, and every “mystery speed drop” in a 5G network becomes a ten-minute investigation.
TS 23.503 §6.1–6.6 (V19.5.0) · TS 32.255 §4.2/§5.1/§5.2/§6.1 (V19.3.0) · TS 23.203 (heritage)Policy & Charging mastery check
Questions and answers reshuffle every load. 70%+ to consider Module 5 done.