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
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (56 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-14, normative work from Rel-15.
In Release 15, the QoS Enforcement Rule (QER) was updated with new attributes to enhance its functionality. These changes were part of a broader set of clarifications for control and user plane functions and the PFCP association procedures. The specification explicitly notes that the QER is only present for QoS Flows within the UPF's packet processing rules.
In Release 16, a key enhancement for the QER function was the introduction of a procedure for "Activating a predefined FAR/URR/QER," allowing these rules to be dynamically enabled within a PFCP session. This built upon the existing framework where the QER is specifically applied for QoS Flows as part of the sequential rule execution following packet detection. The changes also included broader PFCP session management improvements, such as support for sessions being successively controlled by different SMFs within a set.
- Enhancement to the PFCP Association Release Procedure TS 29.244CR0240
- Update the PFCP association setup to support UE IP address Allocation by AAA/DHCP TS 29.244CR0252
- PFCP sessions successively controlled by different SMFs of a same SMF set TS 29.244CR0261
- Measurement Before QoS Enforcement Clarification TS 29.244CR0273
- PFCP messages bundling TS 29.244CR0285
- PFCP sessions controlled by different SMFs in a set TS 29.244CR0270
+ 19 more changes
In Release 17, specific enhancements were made to the QoS Enforcement Rule (QER) function within the PFCP framework. The key update introduced the capability to define the "Number of Reports and Monitoring Time/Measurement Before QoS Enforcement," providing a configurable delay or measurement period before applying QoS enforcement actions. This allows for more granular control and monitoring of traffic conditions prior to enforcement.
- PFCP Node related messages supported over N4mb TS 29.244CR0606
- Transport Level Marking information for PFCP sessions over N4mb TS 29.244CR0622
- Correcting PFCP Associations setup description TS 29.244CR0596
- Return Node ID in PFCP Session Report Response TS 29.244CR0605
- PFCP session related procedures apply to 5GC TS 29.244CR0609
- N4mb requirements for PFCP Node Related messages TS 29.244CR0634
+ 10 more changes
In Release 18, specific corrections and clarifications were made to the QER (QoS Enforcement Rule) function, primarily focusing on the correction of QER indications within the PFCP protocol. These updates were part of broader PFCP session management enhancements, including error handling corrections and procedures for session modification and deletion.
- PFCP extensions for HR-SBO PDU sessions TS 29.244CR0750
- TL-Containers in PFCP Session Modification/Deletion Request/Response TS 29.244CR0767
- PFCP Error Handling Corrections TS 29.244CR0740
- Correction of the QER Indications TS 29.244CR0792
- PFCP Association Release procedure with the MPAS feature TS 29.244CR0802
- Remove Session Report for QoS monitoring measurement at PFCP session deletion TS 29.244CR0807
+ 2 more changes
In Release 19, key enhancements for the QER function's operational context were introduced through improved PFCP session resilience. Specifically, the release defined procedures for excluding certain PFCP sessions from restoration upon an SMF failure and for restoring PFCP sessions at an alternative SMF. These changes ensure that QoS Enforcement Rules, which are applied within PFCP session contexts for QoS Flows, maintain continuity and accurate enforcement during SMF redundancy events.
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 |