Description
Packet Detection Information (PDI) is a fundamental data structure within the 3GPP Packet Forwarding Control Protocol (PFCP), specified primarily in TS 29.244. It is used in the interaction between the Control Plane (CP) function, such as the Session Management Function (SMF) in 5G or the Control Plane part of a Packet Gateway (PGW-C), and the User Plane (UP) function, such as the User Plane Function (UPF) or PGW-U. The PDI is part of a Packet Detection Rule (PDR), which is a complete rule instructing the UP function on how to process packets. The PDI component specifically defines the matching criteria for identifying packets that belong to a particular service data flow.
The PDI contains a list of Information Elements (IEs) that serve as filters. These can include a Source Interface (indicating whether the packet comes from the access side or core network side), network identifiers like the Source/Destination IP address and subnet mask, transport layer identifiers such as Source/Destination port numbers, and application-layer identifiers like the Protocol ID (next header type). In more advanced deployments, it can also include fields for deep packet inspection, such as application identifiers, Service Data Flow (SDF) filters, or even custom enterprise-specific rules. When a packet arrives at the UP function, its header and payload are parsed and compared against all active PDIs. If a match is found, the associated PDR dictates the subsequent actions: forwarding, dropping, buffering, duplicating, or applying Quality of Service (QoS) marking.
Architecturally, the PDI enables the separation of control and user plane, a cornerstone of modern 5G and evolved 4G cores. The control plane function, possessing the full policy context, creates PDIs and installs them via PFCP Session Establishment or Modification procedures. The user plane function then applies these rules at line rate, ensuring low-latency packet processing. The granularity offered by PDI is crucial for implementing network slicing, where different slices require distinct traffic handling. It also forms the basis for traffic detection in policy and charging control (PCC), allowing operators to apply specific charging rates, QoS policies, or gating decisions based on the detected application or service.
In operation, a single PDR contains one PDI but can trigger multiple subsequent actions (Forwarding Action Rules, QoS Enforcement Rules, Usage Reporting Rules). The PDI's matching is typically performed in a defined order of precedence across all installed PDRs. Its design allows for high flexibility and scalability, supporting everything from simple best-effort internet traffic to complex enterprise VPN services with specific security and low-latency requirements. The efficiency of PDI matching directly impacts the overall performance and capacity of the user plane node.
Purpose & Motivation
The creation of Packet Detection Information (PDI) was motivated by the need for a highly flexible, programmable, and standardized method to detect and classify user plane traffic in a control-user plane separated (CUPS) architecture. Prior to CUPS, traffic detection and policy enforcement were tightly integrated within monolithic network nodes like the GGSN or PGW, making it difficult to scale the user plane independently or introduce new services rapidly. The PDI, as part of the PFCP protocol, provides a clean, abstracted interface for the control plane to instruct the user plane on what traffic to look for.
It solves the critical problem of service-aware traffic handling in a high-throughput, low-latency environment. Without a structured detection mechanism like PDI, the user plane would be limited to basic routing based on IP addresses. PDI enables deep packet inspection and classification at the network edge, which is essential for implementing sophisticated policy and charging control (PCC), network slicing, edge computing offload, and parental controls. It allows operators to monetize different service qualities and ensure service level agreements (SLAs) are met.
Historically, traffic detection was embedded in proprietary implementations. Standardizing PDI within PFCP ensured multi-vendor interoperability between control and user plane functions. This was a key enabler for Network Function Virtualization (NFV) and cloud-native deployments, as it allowed operators to source CP and UP functions from different vendors and deploy them elastically. The PDI model, introduced in Release 14 alongside CUPS for the EPC, was later carried forward and enhanced in the 5G Core's Service-Based Architecture (SBA), proving its foundational role in modern packet core networks.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (124 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 PDI (Packet Detection Information) was enhanced to include QFIs (QoS Flow Identifiers) for improved QoS handling and to allow the provision of several SDF filters within a single PDI. The function also gained capabilities for duplicating user plane packets to multiple destinations and for reporting application detection when PFDs are removed. Furthermore, clarifications were provided for the Source Interface in User Plane IP Resource Information and for the overall CP/UP function and PFCP association concepts.
- PDI optimisation TS 29.244CR0071
- Adding QFIs to the Packet Detection Information TS 29.244CR0079
- Duplicating the user plane packets to multiple destinations TS 29.244CR0106
- The Source Interface in the User Plane IP Resource Information TS 29.244CR0108
- Essential clarification on the provision of several SDF filters in a PDI TS 29.244CR0134
- Application detection report when the PFDs are removed TS 29.244CR0154
+ 6 more changes
In Release 16, the PDI (Packet Detection Information) function was enhanced within the PFCP protocol to support new reporting and control mechanisms, as indicated by the introduction of Packet Rate Status Reporting and Control. Furthermore, PDI's role in packet forwarding was extended to support advanced scenarios like traffic offload by a UPF controlled by an I-SMF over the N16a interface and to enable 5GS Bridge information reporting for Time Sensitive Communication. These updates provided more granular control and reporting capabilities for packet detection and handling within the 5G core network's user plane.
- Enhancement to the PFCP Association Release Procedure TS 29.244CR0240
- Update on the Packet Forwarding Model TS 29.244CR0236
- 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
- Number of packets TS 29.244CR0274
- PFCP messages bundling TS 29.244CR0285
+ 31 more changes
In Release 17, the PDI (Packet Detection Information) function was enhanced to support new reporting and control mechanisms over the N4mb interface, specifically for User Plane (In)Activity Detection and Reporting. The release also introduced the ability to carry Transport Level Marking information and additional details like Partial Failure Information within PFCP session procedures. Furthermore, clarifications and corrections were made to the handling of MBS Session N4 Information and PFCP session restoration at UPF restart.
- PMF address information per QoS flow TS 29.244CR0557
- PFCP Node related messages supported over N4mb TS 29.244CR0606
- User Plane (In)Activity Detection and Reporting over N4mb TS 29.244CR0608
- Redirect Port Information TS 29.244CR0613
- Transport Level Marking information for PFCP sessions over N4mb TS 29.244CR0622
- Partial Failure Information TS 29.244CR0570
+ 21 more changes
In Release 18, the PDI (Packet Detection Information) function was enhanced to support new reporting and monitoring capabilities, specifically for congestion information and data rate monitoring as indicated by the new PFCP extensions. These updates enable the UPF to report detailed congestion information and QoS flow-related suggestion information to the CP function. Furthermore, the enhancements included updates to fields within the PDU Set Information and the introduction of a new GTP-U PDU Set Information Container extension header for improved packet handling.
- Direct reporting of TSC Management Information from UPF to TSN AF or TSCTSF TS 29.244CR0725
- Congestion information monitoring TS 29.244CR0724
- Reporting suggestion information for QoS flow related QoS monitoring TS 29.244CR0733
- User plane inactivity detection update TS 29.244CR0731
- Exposure of congestion information TS 29.244CR0739
- PFCP extensions for HR-SBO PDU sessions TS 29.244CR0750
+ 19 more changes
In Release 19, the PDI (Packet Detection Information) function was enhanced to support new packet inspection capabilities for exposing NAT information and for identifying and marking the Data Burst Size in downlink GTP-U packets. Furthermore, the release introduced mechanisms for transferring media-related information over the N6 interface using connect-UDP and UDP Option methods to support end-to-end encrypted traffic. These updates also included refinements for handling application detection information and corrections to the encoding of (S)RTP multiplexed media identification information.
- Supported functionality of NAT information exposure TS 29.244CR0876
- UPF Packet Inspection functionalities TS 29.244CR0881
- PFCP sessions excluded from the restoration upon a SMF failure with SMF set being deployed TS 29.244CR0895
- Transferring media related information over N6 using connect-UDP for e2e encrypted traffic TS 29.244CR0894
- Identification and marking of Data Burst Size in DL GTP-U packets TS 29.244CR0892
- Description for handling of allowed VLAN tags and use of VLAN Handling Information in SMF TS 29.244CR0884
+ 17 more changes
Explore further
Broader topics and technologies where PDI plays a role.
Defining Specifications
3GPP specifications that define or reference PDI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 29.244 vj40 | PFCP Specification for Control/User Plane Separation | Rel-19 |