Description
A Packet Flow Description (PFD) is a data object used within 3GPP's policy and charging control framework to enable application-aware network management. Its primary purpose is to provide the User Plane Function (UPF) or Traffic Detection Function (TDF) with the necessary information to detect traffic belonging to a specific application, such as a video streaming service or a social media app. A PFD is not a rule itself but the descriptive input used to create Packet Detection Rules (PDRs) within the PFCP protocol. A PFD typically contains an application identifier (e.g., a standardized 3GPP App ID or a custom identifier) and one or more packet filters.
These packet filters can be defined at different layers of the protocol stack to allow for flexible and efficient detection. They may include domain names, URLs, URI patterns, or traditional 3-tuple/5-tuple IP information (source/destination IP address, protocol, port numbers). For example, a PFD for a video service might include the domain name of its content delivery network and specific URL patterns for video segments. The entity responsible for PFD management, such as the Policy Control Function (PCF) or an Application Function (AF), provisions these PFDs to the SMF via the N5/N7 interface. The SMF then translates the PFDs into actionable Packet Detection Rules (PDRs) and installs them into the relevant UPF using the PFCP protocol.
Once installed, the UPF uses these derived rules to inspect packets. When a match is found, the UPF can apply the appropriate policy, such as steering the traffic to a specific edge server, applying QoS prioritization, triggering charging events, or blocking the flow. This mechanism is crucial for service differentiation, network optimization, and parental controls. The PFD framework also includes procedures for PFD management, allowing the PCF to provision, update, or remove PFDs dynamically, enabling real-time adjustment to the network's application detection capabilities as new services emerge or traffic patterns change.
Purpose & Motivation
The Packet Flow Description was developed to address the challenge of effectively identifying and managing the exploding variety of Over-The-Top (OTT) application traffic in mobile networks. Traditional policy control relied heavily on static, operator-defined rules based on IP addresses and port numbers, which became ineffective as applications used dynamic ports, encrypted protocols (like HTTPS), and shared content delivery networks, obscuring their identity.
PFDs provide a standardized, flexible method for describing application traffic beyond the limited 5-tuple. By incorporating application-layer identifiers like domain names and URL patterns, they enable much more accurate traffic detection. This accuracy is fundamental for implementing advanced policies like sponsored data (where an application provider pays for the data usage), application-specific QoS boosting (e.g., prioritizing a partner's video service), and intelligent traffic steering to local breakouts or edge caches. The PFD framework, introduced as part of enhanced policy control, empowers operators and third-party service providers to collaborate in creating application-aware networks, moving from managing anonymous IP pipes to managing recognized services and user experiences.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (484 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 PFD (Packet Flow Description) function was enhanced with specific corrections to PFD management procedures to ensure proper application detection. Furthermore, the release introduced the capability for the PFD to contain application data for application detection, as defined for use by the Network Exposure Function (NEF). These updates provided a more robust framework for managing packet flow descriptions within the 5G core network.
- PS Data Off supporting non-IP data packet TS 23.501CR0680
- Corrections to RQoS logic when receiving DL packet with RQI TS 23.501CR0011
- Proposal of Specifying Packet Detection Rule TS 23.501CR0027
- Corrections and clarifications for the usage of Packet Filter Set TS 23.501CR0035
- Updates to the Security Edge Protection Proxy description TS 23.501CR0045
- Traffic mapping information that disallows UL packets TS 23.501CR0053
+ 70 more changes
In Release 16, the PFD (Packet Flow Description) function was enhanced with new management procedures for partial failure scenarios and notifications. Specifically, the release introduced mechanisms for PFD management partial failure and corresponding partial failure notifications. Additionally, the PFD function's capabilities were extended through a defined PFD extension.
- CIoT High Level Description in 23.501 TS 23.501CR0748
- High Latency Overall Description TS 23.501CR0751
- General description of solution 1 in 23.725 for user plane redundancy TS 23.501CR0753
- Add description of solution 4 in 23.725 to 23.501 TS 23.501CR0811
- Description of solution 7 in 23.725 as replication framework TS 23.501CR0872
- Description of solution 11 in 23.725 for Ethernet anchor relocation TS 23.501CR0755
+ 89 more changes
In Release 17, the PFD (Packet Flow Description) function was enhanced to support the PATCH method for updating a PFD Management Transaction resource, allowing for more efficient partial modifications. This update included a description of using a JSON body with "JSON Patch" encoding to specify the changes. These improvements provided a more flexible and standardized mechanism for the NEF to manage PFDs for application detection.
- Packet Loss Rate measurements TS 23.501CR2587
- Function Description for Multi-SIM devices TS 23.501CR2553
- EASDF discovery and selection and update of edge computing description TS 23.501CR2707
- NSACF functional descriptions TS 23.501CR2727
- Fix the description on the ethernet port TS 23.501CR2820
- ProSe related functional description TS 23.501CR2861
+ 121 more changes
In Release 18, the PFD (Packet Flow Description) function was enhanced to support Packet Delay Variation (PDV) monitoring and reporting as a new QoS monitoring parameter, which is controlled by the PCF and can be exposed to an Application Function. Additionally, updates were made to the flow description handling for a list of UEs and to the protocol description for end-of-burst indication.
- PCF support of 5GS Packet Delay Variation monitoring based on QoS monitoring mechanism and exposed to AF TS 23.501CR3792
- Support for network timing synchronization status and reporting KI1 - description TS 23.501CR3892
- Add description for PSA UPF selection TS 23.501CR3985
- Update the descriptions for supporting Edge Computing on satellite TS 23.501CR4293
- Update about the Packet Delay Variation description and add PDV in QoS monitoring parameters TS 23.501CR4506
- Basic description of Service Function Chaining TS 23.503CR0740
+ 128 more changes
In Release 19, key enhancements to the Packet Flow Description (PFD) function included specific enhancements on PFD provisioning procedures. The release also introduced new UPF packet inspection functionalities, which enable more detailed application detection and traffic management. Furthermore, it added support for the identification and marking of Data Burst Size within downlink GTP-U packets, providing greater visibility into data flow characteristics.
- Adding the NAT information exposure and Packet Inspection functionality in the UPF NF profile TS 23.501CR5420
- Adding 5G Femto support description TS 23.501CR5488
- General description of relaying media related information over N6 using an encapsulation protocol TS 23.501CR5711
- Functional Description of Energy Efficiency Control Functionality TS 23.501CR5740
- UPF Packet Inspection functionalities TS 29.244CR0881
- Identification and marking of Data Burst Size in DL GTP-U packets TS 29.244CR0892
+ 46 more changes
Explore further
Broader topics and technologies where PFD plays a role.
Defining Specifications
3GPP specifications that define or reference PFD, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.503 vk00 | 5G Policy and Charging Control Framework | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 26.512 vj10 | 5G Media Streaming Protocols & APIs | Rel-19 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TS 29.122 vj40 | T8 Reference Point for Northbound APIs | Rel-19 |
| TS 29.212 vj00 | Gx/Gxx/Sd/St Diameter Protocol | Rel-19 |
| TS 29.244 vj40 | PFCP Specification for Control/User Plane Separation | Rel-19 |
| TS 29.250 vj00 | Nu Reference Point Stage 3 Specification | Rel-19 |
| TS 29.251 vj00 | Gw/Gwn Reference Points Stage 3 Specification | Rel-19 |
| TS 29.510 vj50 | NRF Service Based Interface Protocol | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.519 vj40 | UDR Usage for Policy & Exposure Data | Rel-19 |
| TS 29.520 vj40 | 5G Network Data Analytics Services Stage 3 | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.551 vj30 | 5G PFD Management Service Stage 3 | Rel-19 |
| TS 38.101 vj31 | NR User Equipment Radio Transmissions | Rel-19 |