TSN

AF Time Sensitive Networking Application Function

Services →
Introduced in Rel-5 Also in: Radio Access Network, Services, Management

TSN is an Application Function in the 5G Core that interfaces with external Time-Sensitive Networking systems, translating their requirements into 5G network policies to enable deterministic, low-latency connectivity for industrial automation.

Category
Services
Introduced
Rel-5
Where
Core Network › 5G Core
Also touches
3 segments
Specifications
35 specs
TSN Description Purpose Related Classification Detected Changes Specifications

Description

The TSN Application Function (TSN AF) is a critical component defined by 3GPP for integrating 5G systems into IEEE 802.1 Time-Sensitive Networking (TSN) ecosystems, which are central to industrial Ethernet and deterministic communication. It resides in the 5G Core network as a specialized Application Function, interacting with other core network functions like the Policy Control Function (PCF) and Network Exposure Function (NEF) via service-based interfaces. The TSN AF's primary role is to represent the TSN network (or the TSN System) to the 5G system, acting as a gateway for TSN-specific configuration and requirements.

Architecturally, the TSN AF interfaces with a TSN Network Controller (or Centralized Network Controller - CNC), which is the entity in the TSN domain responsible for overall schedule and resource management. The TSN AF receives TSN requirements from the CNC, which include deterministic communication parameters such as periodicity, maximum latency, reliability (packet error rate), and time synchronization accuracy for data flows that will traverse the 5G system. The 5G system, in this context, is modeled as a virtual TSN bridge (or a set of bridges) from the TSN network's perspective. The TSN AF is responsible for making the 5G system's capabilities and resources visible to the TSN CNC and for mapping the TSN flow requirements into 5G-specific QoS parameters and policies.

How it works involves a multi-step process. First, during capability exposure, the TSN AF informs the TSN CNC about the 5G system's characteristics, such as supported latency bounds, time synchronization support (via 5G system as a timing slave or master), and available bandwidth. When the CNC computes a global schedule for TSN traffic, it includes the 5G virtual bridge. The CNC sends this schedule, including gate control lists for the 5G bridge ports, to the TSN AF. The TSN AF then translates these TSN constructs into 5G policy rules. It interacts with the PCF to create or modify PCC (Policy and Charging Control) rules that enforce the required QoS—for example, by allocating a dedicated 5G QoS Flow with guaranteed bit rate and packet delay budget for a specific TSN stream. It may also interact with the SMF (Session Management Function) and UPF (User Plane Function) to configure the user plane for deterministic forwarding.

Key components it interacts with include the TSN Translator in the UE and/or in the UPF, which handle the actual adaptation of Ethernet frames to 5G packets and vice versa, including timestamping for synchronization. The TSN AF's role is purely in the control plane, managing the configuration. It enables end-to-end deterministic connectivity where a 5G wireless link can be seamlessly integrated into a wired TSN network, supporting critical Industry 4.0 applications like motion control, machine vision, and closed-loop control systems that require ultra-reliable, low-latency, and time-synchronized communication.

Purpose & Motivation

The TSN AF was created to bridge two historically separate worlds: deterministic industrial networking (TSN) and cellular mobile networks (5G). Industrial automation has long relied on wired fieldbus and industrial Ethernet technologies (like PROFINET, EtherCAT) that provide hard guarantees on latency, jitter, and synchronization. These are essential for coordinating machines on a production line. Wireless solutions were traditionally unsuitable due to lack of determinism, reliability, and precise timing.

The advent of 5G, with its URLLC (Ultra-Reliable Low-Latency Communication) capabilities, promised to break this barrier, enabling flexible wireless connectivity for moving parts like AGVs (Automated Guided Vehicles) and robotic arms. However, simply providing a low-latency pipe was not enough. For true integration, the 5G network needed to appear as a standard, manageable component within the TSN ecosystem, which is controlled by a central CNC. The TSN AF solves this problem by acting as the 5G system's agent to the TSN control plane.

It addresses the key limitation of previous wireless solutions—their opacity and lack of deterministic scheduling integration. Without the TSN AF, a TSN CNC could not see or control the 5G link, making end-to-end deterministic scheduling impossible. The TSN AF provides the necessary translation layer, allowing the CNC to treat the 5G radio link as just another TSN bridge with known characteristics. This motivated its creation in 3GPP Release 16 as part of the 5G system's support for vertical industries, specifically factory automation. It enables the convergence of OT (Operational Technology) and IT networks, allowing 5G to become a viable replacement for cables in the most demanding industrial control applications, thereby enabling new levels of flexibility and reconfigurability in smart manufacturing.

Classification

Specific typesNW-TT
Related approachesURLLC

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (233 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Studied in Rel-5, normative work from Rel-15.

Rel-15 10 changes

In Release 15, the TSN AF function was introduced with foundational architectural enhancements to facilitate 5G system communications with time-sensitive applications and packet data networks. The release included specific clarifications and fixes for application-related procedures, such as the association of an S-NSSAI to a given application and the handling of application detection reports. Furthermore, it defined mechanisms for application error reporting and the priority configuration between application traffic routing policies (URSP) and network access identifiers (LADN DNN).

  • 5G QoS fixes for URLLC services related attributes - PDB, PER, MDB, 5QI TS 23.501CR0087
  • Clarification on the association of an S-NSSAI to a given application TS 23.501CR0154
  • Clarification on Application data TS 23.501CR0242
  • Application detection report when the PFDs are removed TS 23.501CR0485
  • Clarification on priority of URSP and configuration of association between application and LADN DNN TS 23.501CR0609
  • Application Error POLICY_CONTEXT_DENIED TS 29.512CR0098

+ 4 more changes

Rel-16 96 changes

In Release 16, the TSN AF saw the introduction of specific containers for transporting TSN QoS and TSCAI information between network functions like the SMF, PCF, and AF, and it gained the ability for the PCF to provision TSN-related Policy Control Request triggers. Furthermore, the release defined mechanisms for AF session binding to a PDU Session for TSN networks and enhanced QoS parameter mapping between TSN characteristics and 5G QoS parameters.

  • 5GS Logical TSN bridge management TS 23.501CR1002
  • New clause for URLLC supporting TS 23.501CR0810
  • QoS parameters mapping between TSN characters and 5G QoS TS 23.501CR1003
  • TSN QoS mapping and 802.1Qbv parameters TS 23.501CR1123
  • Introduction of TSN Sync soln #28A TS 23.501CR1381
  • Introduction of QoS Monitoring to assist URLLC Service TS 23.501CR0990

+ 90 more changes

Rel-17 61 changes

In Release 17, the TSN AF function was expanded to introduce a new architecture for AF-requested support of Time Sensitive Communication (TSC) and Time Synchronization, enabling unified support for TSC/TSN services. This release specifically added support for Time Sensitive Communication other than TSN, broadening the scope beyond traditional IEEE TSN networks. These updates facilitated architecture enhancements for communications with packet data networks and applications.

  • Network slice adaptation for VAL applications TS 23.434CR0032
  • Unified support for TSC/TSN services TS 23.434CR0064
  • Editorial re-application of CR0043r3 "Off-network location management" TS 23.434CR0043
  • Introduction of the architectures for Time Sensing Communication other than TSN. TS 23.501CR2573
  • Adding the usage of Redundant Transmission Experience analytics for URLLC service TS 23.501CR2581
  • KI#2 BMIC and PMIC for TSC without IEEE TSN network TS 23.501CR2618

+ 55 more changes

Rel-18 49 changes

In Release 18, the TSN AF enhancements included new support for direct reporting of TSC Management Information from the UPF to the TSN AF or TSCTSF and the introduction of a TL-Container for TSN-enabled transport network integration. Furthermore, the release focused on improved interworking with TSN networks deployed in the transport layer and added specific UP Function features to bolster Time Sensitive Communication and synchronization capabilities.

  • Application level control signalling over 5G MBS sessions TS 23.434CR0124
  • Coordinated application-level direct UE-to-UE communications TS 23.434CR0215
  • Interworking with TSN network deployed in the transport network TS 23.501CR3811
  • Support of integration with IETF Deterministic Networking TS 23.501CR3844
  • Removing ENs for TSN TN integration TS 23.501CR3870
  • Assistance to Member Selection Functionality for Application Operation TS 23.501CR3910

+ 43 more changes

Rel-19 16 changes

In Release 19, the TSN (AF Time Sensitive Networking Application Function) saw specific enhancements, including corrections to the mapping of parameters between the 5GS and the TSN User Network Interface (UNI) to ensure proper interoperability. This release also provided clarifications on the handling of application detection reports and the start or stop procedures for an application and application instance, refining the overall application enablement framework.

  • General description of application enablement of AIML services TS 23.434CR0312
  • Application QoS coordination for Mobile Metaverse Services TS 23.434CR0336
  • Support of Application satellite coverage availability information configuration TS 29.549CR0382
  • Rel-19 CR 32.255 Add volume based charging principle for DC application download and usage TS 32.255CR0575
  • Rel-19 CR 32.291 Charging information for IMS DC application download charging TS 32.291CR0618
  • Adding per UE per Application level Energy consumption exposure TS 23.501CR6028

+ 10 more changes

Rel-20 1 change

In Release 20, the enhancement for the TSN Application Function introduced a capability to expose per-UE application ranking related information. This new functionality is facilitated through the exposure framework, specifically involving the EIF. The change enables the network to provide ranking information for individual applications on a per-user equipment basis.

  • KI#1: Per UE application ranking related information exposed by EIF TS 23.501CR6501

Explore further

Broader topics and technologies where TSN plays a role.

Topics
Policy & ChargingLawful InterceptManagement & OperationsProtocols & InterfacesRadio Access NetworkCore Network
Technologies
5G

Defining Specifications

3GPP specifications that define or reference TSN, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TR 21.905 vj00 3GPP Technical Terms and Definitions Rel-19
TS 22.821 vg10 5G LAN-type Services Requirements Rel-16
TS 23.434 vk00 Service Enabler Architecture for Verticals Rel-20
TS 23.501 vk00 5G System Architecture Stage 2 Rel-20
TS 23.725 vg20 Study on URLLC Architecture Enhancements Rel-16
TR 23.745 vh00 Study on App Layer Support for Factories of the Future in 5G Rel-17
TS 24.501 vj50 5G NAS Protocols Specification Rel-19
TS 24.519 vh10 TSN AF to DS-TT/NW-TT Protocol Aspects Rel-17
TS 24.535 vj00 TS 24535: (g)PTP Message Delivery Protocol Rel-19
TS 24.539 vj30 NW-TT Protocol Aspects Rel-19
TS 25.301 vj00 UE-UTRAN Radio Interface Protocol Architecture Rel-19
TS 25.302 vj00 UTRA Physical Layer Services Rel-19
TS 25.308 vj00 HSDPA Overall Description Rel-19
TS 25.309 v1600 FDD Enhanced Uplink Support Rel-6
TS 25.319 vj00 Enhanced Uplink for UTRA FDD/TDD Rel-19
TS 25.321 vj00 MAC Protocol Specification for UTRAN Rel-19
TS 25.331 vj00 UTRAN RRC Protocol Specification Rel-19
TR 28.839 vi10 Technical Report Rel-18
TR 28.843 vi10 Technical Report on Charging Aspects for Vertical Scenarios Rel-18
TS 29.244 vj40 PFCP Specification for Control/User Plane Separation 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 29.549 vj40 SEAL API Specification for Vertical Applications Rel-19
TS 29.564 vj50 Nupf Service Based Interface Protocol Rel-19
TS 29.585 vj00 TSN Interworking Protocol for 5G System Rel-19
TS 29.889 vj10 Study on UPF data collection for AI/ML Rel-19
TS 32.240 vj40 Charging Management Architecture & Principles Rel-19
TS 32.255 vk10 Telecom Management; Charging for 5G Data Connectivity Rel-20
TS 32.282 vi20 Charging management; Time Sensitive Networking Rel-18
TS 32.290 vj50 5G Charging for Service Based Interface Rel-19
TS 32.291 vj40 Charging Management: Service-Based Interface Protocol Rel-19
TS 32.297 vj00 Charging Data Record File Transfer Rel-19
TR 33.851 vh10 Security for Industrial IoT in 5G Rel-17
TR 38.825 vg00 Study on NR Industrial IoT Rel-16