Description
The User Plane Function (UPF) is a fundamental network function within the 5G Core (5GC) based on the Service-Based Architecture (SBA). It is responsible for all tasks related to the processing and forwarding of user data packets. The UPF acts as the interconnect point between the Radio Access Network (RAN) – either NG-RAN or non-3GPP access – and external Data Networks (DNs), such as the internet or operator services. Its architecture is designed to be highly flexible and distributable, allowing multiple UPF instances to be deployed in different parts of the network (e.g., central, regional, edge locations) to meet diverse latency and bandwidth requirements.
How the UPF works is governed by rules installed by the Session Management Function (SMF). The SMF provisions Packet Detection Rules (PDRs), Forwarding Action Rules (FARs), QoS Enforcement Rules (QERs), and Usage Reporting Rules (URRs) into the UPF via the N4 interface. Upon receiving a packet, the UPF inspects it (matching against PDRs) and executes the associated actions. These actions can include forwarding the packet to a specific tunnel or interface (FAR), applying QoS marking and rate limiting (QER), measuring traffic volume for charging (URR), and even duplicating packets for analytics or redundancy. A single UE session may involve multiple UPFs, such as a branching point UPF for multi-homed connectivity or an intermediate UPF for localized breakouts.
Key components of the UPF's role include being the anchor point for mobility—both intra-system and between 3GPP and non-3GPP access. It provides the external PDU Session interface, making it the official 'exit point' of the 5G network. Furthermore, the UPF is the critical enabler for several advanced 5G capabilities. For Network Slicing, different UPF instances can be dedicated to specific slices, providing isolated data paths. For Edge Computing, the UPF can be deployed at the network edge to locally route traffic to nearby application servers, drastically reducing latency. It also performs deep packet inspection for application-aware steering and supports features like traffic aggregation and IPv6 multi-homing.
Purpose & Motivation
The UPF was created as part of the clean-slate design of the 5G Core network to address the limitations of the 4G EPC's user plane, particularly the split SGW/PGW architecture. The motivations were to achieve greater flexibility, scalability, and support for new service paradigms. Key problems it solves include: enabling ultra-low latency services by allowing decentralized deployment at the network edge; providing the architectural foundation for end-to-end network slicing by offering an isolatable data plane component; and supporting a wider range of access technologies (5G NR, LTE, Wi-Fi, fixed) with a unified anchor point.
Historically, the 4G EPC gateways (SGW, PGW) were monolithic entities with control and user plane tightly coupled, making them difficult to scale independently and deploy flexibly. The 5G design principles of cloud-nativity, SBA, and Control and User Plane Separation (CUPS) directly led to the UPF's creation. The UPF is a pure, scalable user plane element that can be instantiated on demand anywhere in the network cloud. This addresses the need for a dynamic, software-driven architecture capable of supporting diverse 5G use cases, from enhanced mobile broadband (eMBB) to massive IoT (mIoT) and critical communications, each with distinct bandwidth, latency, and reliability requirements.
Architecture
In the Network Map
- Mobile Network → 5G Core → UPF (User Data & Packet Gateway)
- Mobile Network → NG-RAN → UPF (5G Core (context))
Evolution Lineage
- Evolved from: S-GW (4G→5G), PGW (4G→5G)
- Network evolution overview →
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (200 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the UPF was formally introduced as the 5G Core's dedicated User Plane Function, centralizing packet routing and forwarding. New capabilities included support for N4 interface management with the SMF, procedures for UPF discovery via the NRF, and specific handling for PDU session establishment and restoration, including mechanisms for UPF restart recovery. Furthermore, the release defined the UPF's role in legal interception, QoS enforcement, and specialized packet detection for services like IMS.
- Using NRF for UPF discovery TS 23.501CR0002
- Corrections to UPF selection and resolution of related Editor's Note TS 23.501CR0044
- Select the same SMF+UPF for PDU sessions of the same DNN within one slice TS 23.501CR0187
- Clarification on handling of Ethernet frames at UPF TS 23.501CR0497
- Clarification for QoS handling at UPF TS 23.501CR0502
- Subscription of selecting the same SMF and UPF TS 23.501CR0515
+ 7 more changes
In Release 16, new UPF capabilities were introduced, including UE IP address allocation directly by the UPF with N4 interface impacts, and enhanced selection mechanisms influenced by 5G AN N3 User Plane capability and analytics. The UPF gained roles in supporting ATSSS, traffic offload controlled by the I-SMF, and providing residence time information for Time-Sensitive Communication (TSC) deterministic QoS. Furthermore, the release specified procedures for UPF failure detection and recovery for IMS services, including the UPF's role in reporting RTCP Receiver Report packets to trigger dedicated IMS bearer establishment.
- ATSSS-SMF and UPF selection TS 23.501CR0761
- UPF Selection influenced by the indication of the identity/identities of 5G AN N3 User Plane capability TS 23.501CR0862
- Use of analytics for user plane function selection TS 23.501CR0899
- UE IP address Allocation by UPF: N4 impacts TS 23.501CR0931
- Addition of UE IP address Allocation by UPF TS 23.501CR0954
- Traffic offload by UPF controlled by the I-SMF TS 23.501CR1179
+ 40 more changes
In Release 17, the UPF saw enhancements focused on failure resilience and new analytics capabilities. Specifically, it introduced procedures for MBS (Multicast/Broadcast Service) session restoration upon MB-UPF failure, both with and without restart, and defined UPF behavior for P-CSCF failure detection to speed up IMS session recovery. Furthermore, the release added support for UPF information exposure for service experience and DN performance analytics, and extended the UPF's role in forwarding specific message types like (g)PTP and DNS messages.
- PMF extensions for sending UE-assistance data to UPF TS 23.501CR2647
- UPF function update to support network information exposure TS 23.501CR2900
- Use UPF to transfer DNS message between EASDF and DNS server TS 23.501CR3186
- MBS session restoration upon MB-UPF failure with restart TS 23.527CR0041
- MBS session restoration upon MB-UPF failure without restart TS 23.527CR0042
- UPF behaviour of setting source and destination addresses of PMF message TS 29.244CR0580
+ 27 more changes
In Release 18, the UPF saw significant enhancements in event exposure and service integration, including new support for Satellite Edge Computing and local switching via satellite-deployed UPFs. The release introduced UPF event exposure services for TSC management and QNC, enabled direct reporting to TSN AF/TSCTSF, and expanded UPF's role as a data source for NWDAF analytics. Furthermore, it added procedures for UPF discovery considering event exposure capabilities, N6 tunneling for HR-SBO sessions, and updates to UPF event subscription and notification mechanisms via the SMF.
- Update for UPF registration and event exposure related context concluded in FS_UPEAS TS 23.501CR3723
- Support of Satellite Edge Computing via UPF deployed on satellite TS 23.501CR3793
- Support of local switch via UPF deployed on satellite for GEO backhaul case TS 23.501CR3794
- UPF event exposure service for TSC management TS 23.501CR3720
- Add description for PSA UPF selection TS 23.501CR3985
- Clarification of N19 forwarding for local switch via PSA UPF on GEO TS 23.501CR3999
+ 60 more changes
In Release 19, the UPF enhancements focused on improved event exposure and health monitoring, including UPF event exposure during UPF relocation or PDU session release and direct subscription to UPF event exposure using a UE IP address. Furthermore, the release introduced UPF health check and failure recovery procedures, particularly for IMS sessions, and expanded UPF selection capabilities to consider factors like N6 delay. These updates also included corrections to UPF selection and enhancements to QoS monitoring and reporting during session mobility events.
- Adding the NAT information exposure and Packet Inspection functionality in the UPF NF profile TS 23.501CR5420
- Support of UPF selection according to the conclusion in FS_UPEAS_Ph2 TS 23.501CR5441
- Supporting direct subscription of UPF event exposure using UE's IP address TS 23.501CR5540
- UPF event exposure during UPF relocation TS 23.501CR5565
- Support of L-PSA UPF Selection Considering N6 Delay TS 23.501CR5437
- Updates to UPF data exposure for KI#2 direct subscription TS 23.501CR5452
+ 36 more changes
Explore further
Broader topics and technologies where UPF plays a role.
Defining Specifications
3GPP specifications that define or reference UPF, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.380 vj10 | IMS Restoration Procedures | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.527 vj50 | 5G System Restoration Procedures | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.758 vh00 | Study on Edge Application Architecture | Rel-17 |
| TS 24.193 vj50 | ATSSS Procedures Specification | Rel-19 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.502 vj20 | 5G Core Access via Non-3GPP Networks; Stage 3 | Rel-19 |
| TS 26.113 vj10 | 5G Real-Time Media Communication Procedures & APIs | Rel-19 |
| TS 26.501 vj30 | 5G Media Streaming (5GMS) Architecture | Rel-19 |
| TS 26.522 vj30 | RTP for XR in 5G Systems | Rel-19 |
| TS 26.802 vj20 | Multicast Enhancements for 5G Media Streaming | Rel-19 |
| TR 26.803 vh00 | 5G Media Streaming Extensions for Edge Processing | Rel-17 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TR 26.806 vi00 | Technical Report on Smartly Tethering AR Glasses | Rel-18 |
| TS 26.822 vj20 | 5G RTP Configurations Study Phase 2 | Rel-19 |
| TR 26.857 vi00 | Technical Report on Media Service Enablers | Rel-18 |
| TS 26.891 vg00 | Media Distribution Services in 5G System | Rel-16 |
| TR 26.919 vj00 | Study on 5G Conversational Media Handling | Rel-19 |
| TR 26.926 vj00 | Traffic Models & Quality Evaluation for Media/XR in 5G | Rel-19 |
| TR 26.942 vj00 | Study on Media Energy Consumption Exposure & Evaluation | Rel-19 |
| TS 28.802 vf00 | Management Study for 5G Network Architecture | Rel-15 |
| TR 28.822 vh00 | Charging for 5G LAN Services Study | Rel-17 |
| TR 28.833 vi01 | Technical Report on 5G LAN-type Service Management | Rel-18 |
| TR 28.836 vi00 | Technical Report on Intent Driven Management | Rel-18 |
| TS 28.874 vj10 | Study on Management Aspects of NTN Phase 2 | Rel-19 |
| TS 29.244 vj40 | PFCP Specification for Control/User Plane Separation | Rel-19 |
| TS 29.502 vj50 | 5G System; Nsmf Service Based Interface; Stage 3 | Rel-19 |
| TS 29.508 vj40 | 5G Session Management Event Exposure Service | 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 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | 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 29.523 vj20 | 5G Policy Control Event Exposure Service | Rel-19 |
| TS 29.532 vj30 | MB-SMF Service Based Interface Protocol | Rel-19 |
| TS 29.552 vj40 | 5G Network Data Analytics Signalling Flows | Rel-19 |
| TS 29.561 vj30 | 5G Interworking with External Data Networks | Rel-19 |
| TS 29.564 vj50 | Nupf Service Based Interface Protocol | Rel-19 |
| TS 29.574 vj40 | 5G Data Collection Coordination Services Stage 3 | Rel-19 |
| TS 29.575 vj40 | 5G Analytics Data Repository Services Stage 3 | Rel-19 |
| TS 29.585 vj00 | TSN Interworking Protocol for 5G System | Rel-19 |
| TR 29.820 vh00 | Study on PFCP Best Practice | Rel-17 |
| TS 29.866 vj00 | IMS Disaster Prevention & Restoration Enhancement | Rel-19 |
| TS 29.889 vj10 | Study on UPF data collection for AI/ML | Rel-19 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 29.892 vg00 | Study on User Plane Protocol in 5GC | Rel-16 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.279 vj00 | 5G MBS Session Converged Charging | Rel-19 |
| TS 32.899 vf10 | 5G Charging Architecture Study | Rel-15 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.501 vk00 | 5G Security Architecture and Procedures | Rel-20 |
| TS 33.515 vk00 | 5G SMF Security Assurance Specification | Rel-20 |
| TR 33.739 vi10 | Study on security enhancement of support for | Rel-18 |
| TS 33.749 vj00 | Study on security aspects of edge computing enhancement | Rel-19 |
| TS 33.835 vg10 | Study on authentication and key management for apps | Rel-16 |
| TR 33.851 vh10 | Security for Industrial IoT in 5G | Rel-17 |
| TS 33.861 vg10 | CIoT Security Evolution for 5G System | Rel-16 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.410 vj10 | NG Interface Introduction for NG-RAN to 5GC | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.414 vj00 | NG Interface User Plane Protocol | Rel-19 |
| TS 38.415 vj10 | PDU Session User Plane Protocol | Rel-19 |
| TS 38.423 vj10 | Xn Application Protocol (XnAP) specification | Rel-19 |
