Description
The QoS Enforcement Rule (QER) is a core element of the 5G Policy and Charging Control (PCC) architecture, specified in 3GPP TS 29.244 (PFCP protocol) and TS 26.804 (codec-specific aspects). A QER is a container of instructions that dictates how the User Plane Function (UPF) should handle packets belonging to a specific Protocol Data Unit (PDU) Session or QoS Flow. It is created, modified, or removed by the Session Management Function (SMF) based on policies received from the Policy Control Function (PCF) using the N7 reference point.
Each QER contains several key information elements that define its enforcement behavior. This includes a QER Identifier, the QoS Flow Identifier (QFI) to which it applies, and a set of enforcement actions. The primary actions are Gate Status (open/close), which controls whether packets are allowed to pass, and QoS Enforcement parameters. The QoS parameters typically include the Guaranteed Flow Bit Rate (GFBR), Maximum Flow Bit Rate (MFBR), and optionally, an Aggregate Bit Rate (ABR) for the flow. The UPF uses these parameters to perform policing, marking, and scheduling of packets to ensure the contracted QoS is delivered.
Operationally, QERs are installed in the UPF via the Packet Forwarding Control Protocol (PFCP) Session Modification procedure. The SMF sends a PFCP Session Modification Request containing one or more QERs to be applied. The UPF then installs these rules in its fast-path data plane, where they are matched against incoming packets based on filters like the QFI. Enforcement involves metering the traffic against the configured bit rates, dropping or marking (e.g., setting Drop Eligibility Indicator) packets that exceed limits, and ensuring minimum guaranteed rates are sustained. This mechanism allows for highly dynamic and service-specific QoS treatment, which is central to 5G's network slicing and service-based architecture.
Purpose & Motivation
QoS Enforcement Rules (QERs) were introduced in 3GPP Release 14, initially for LTE Advanced Pro, and became central to the 5G Core (5GC) defined in Release 15. Their creation was driven by the need for more flexible, dynamic, and granular QoS enforcement beyond the static QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP) mechanisms of 4G EPS. Previous systems lacked the ability to dynamically adjust bit rate guarantees and enforcement policies on a per-flow basis during an active session, which limited support for novel services with highly variable bandwidth demands.
The primary problem QERs solve is enabling network-slicing and service-specific QoS guarantees. In 5G, a single PDU Session can contain multiple QoS Flows with different requirements (e.g., one for enhanced mobile broadband and another for ultra-reliable low-latency communication). QERs provide the tool for the PCF and SMF to instruct the UPF on how to police and shape each flow independently and in real-time. This is crucial for meeting Service Level Agreements (SLAs) for diverse use cases like industrial IoT, autonomous vehicles, and augmented reality.
Furthermore, QERs facilitate the separation of control and user plane in 5G. By defining a standardized rule format communicated via PFCP, they allow a centralized PCF/SMF to control distributed UPFs efficiently. This architectural shift supports cloud-native deployment and scalability. QERs thus represent a key evolution towards software-defined, policy-driven QoS management that can adapt to rapidly changing application needs and network conditions.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (4 CRs across 3 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the QoS Enforcement Rule (QER) was introduced as a new, non-mandatory function for controlling QoS Flows. The release specifically included updates to the attributes used within the QER. This rule is executed based on Packet Detection Rule (PDR) results alongside other rules like the Forward Action Rule (FAR).
- Update attributes in QER TS 29.244CR0091
In Release 16, the QER function was enhanced to allow its explicit activation as a predefined rule, providing more dynamic control over QoS enforcement. Furthermore, the procedures for modifying a session were clarified to include the creation of QER Information Elements within a modification message. These changes improved the flexibility and precision of managing QoS rules for QoS Flows within the system.
In Release 18, a specific correction was made to the QER (QoS Enforcement Rule) Indications. This update refined the signaling or procedural details for how QERs, which are only present for QoS Flows, are managed within the system. The change ensures the QER function operates correctly in conjunction with other packet flow rules like the FAR and URR.
- Correction of the QER Indications TS 29.244CR0792
Explore further
Broader topics and technologies where QER plays a role.
Defining Specifications
3GPP specifications that define or reference QER, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TS 29.244 vj40 | PFCP Specification for Control/User Plane Separation | Rel-19 |
