QoS Dictionary (QoS)¶
A lightweight dictionary for looking up the key terms of the 5G QoS model by meaning and usage. For the detailed mechanics, see the QoS chapter.
Related: QoS chapter / PFCP Dictionary / Interface Dictionary / PDU Session chapter
QoS term list¶
| Term | Full name | Meaning | Usage/Notes | Spec |
|---|---|---|---|---|
| QoS Flow | QoS Flow | The finest granularity of QoS control within a PDU session. A bundle of packets that receive the same QoS | QoS control is performed on a per-QoS Flow basis | TS 23.501 |
| QFI | QoS Flow Identifier | A value that identifies a QoS Flow | Attached to packets in the user plane (N3/N9 PDU Session Container = TS 38.415) | TS 23.501 / TS 38.415 |
| 5QI | 5G QoS Identifier | A scalar value pointing to QoS characteristics (priority/delay/error rate) | There are standardized 5QIs and dynamic assignment. The mapping table of concrete values is to be confirmed against the table in TS 23.501 | TS 23.501 |
| GBR | Guaranteed Bit Rate | Guaranteed-bit-rate type flow | Used for voice/real-time, etc. | TS 23.501 |
| Non-GBR | Non-Guaranteed Bit Rate | Non-guaranteed type flow (best effort) | General data communication, etc. | TS 23.501 |
| ARP | Allocation and Retention Priority | Allocation and retention priority | Controls whether resources can be allocated and preemption under congestion | TS 23.501 |
| Session-AMBR | Session Aggregate Maximum Bit Rate | Per-PDU-session aggregate cap for Non-GBR | The upper limit on the sum of Non-GBR flows within a session | TS 23.501 |
| UE-AMBR | UE Aggregate Maximum Bit Rate | Per-UE aggregate cap for Non-GBR | Notified to the RAN over N2 | TS 23.501 / TS 38.413 |
| QoS Rule | QoS Rule (NAS/5GSM) | The packet ↔ QoS Flow mapping rule notified to the UE | Classifies to a flow via packet filters (IE Dictionary) | TS 24.501 |
| QoS Flow Description | QoS Flow Description | A description of a QoS Flow's characteristics | Notified to the UE over NAS | TS 24.501 |
| Reflective QoS (RQoS) | Reflective QoS | A mechanism by which the UE reflectively applies uplink QoS based on the downlink direction | The UE derives rules automatically | TS 23.501 |
| GFBR/MFBR | Guaranteed/Maximum Flow Bit Rate | Guaranteed/maximum flow bit rate of a GBR flow | Specifies the bandwidth characteristics of a GBR flow | TS 23.501 |
Grasp QoS by its hierarchy
QoS is easier to organize when understood as a hierarchy of PDU session (Session-AMBR) > QoS Flow (QFI/5QI/GBR characteristics) > packet (classified to a flow by QoS Rule). In the user plane, the QFI is attached to packets (the PDU Session Container of N3/N9), and the UPF applies QoS via the QER (PFCP Dictionary). For the detailed mechanics, see the QoS chapter.