TSN

What is TSN?

TSN (Time-Sensitive Networking) is a set of IEEE 802.1 standards that extends standard Ethernet with time synchronisation, time-based traffic scheduling, frame preemption and redundancy, so that time-critical data is delivered with a guaranteed, bounded latency. This lets real-time control and motion control traffic run over the same network as ordinary IT traffic such as video, file transfers or web traffic. TSN is not a protocol in itself but a toolbox of functions from which industrial protocols such as ProfiNET, OPC UA FX and CC-Link IE TSN make their selection.

TSN does not promise that there is never any delay. It promises that the delay for scheduled traffic is predictable and bounded, however much other traffic is on the network.

🧠 Where does TSN come from?

TSN grew out of Audio Video Bridging (AVB), an IEEE 802.1 task group that from 2005 onwards developed reliable audio and video streaming over Ethernet for stages, studios and cars. The credit-based shaper (802.1Qav, 2009) and the first edition of the 802.1AS time synchronisation standard (2011) date from that period.

In November 2012 the AVB Task Group was renamed the Time-Sensitive Networking Task Group. Its scope widened: not just media, but also hard real-time requirements from industrial automation, the automotive industry and telecoms. New requirements came with it, such as fault tolerance and reconfiguring traffic while the network is running.

The idea behind TSN fits Industry 4.0 and the IIoT: instead of separate networks for control, safety, video and office IT, a single converged network gives every data flow the guarantees it needs.

🔧 Which IEEE standards make up TSN?

TSN is a family of standards. Many were published as amendments and later rolled into the base standard IEEE 802.1Q.

For industry, the core is the combination of 802.1AS, 802.1Qbv and 802.1Qbu/802.3br: a shared time base, a fixed schedule and a way to stop a large frame from blocking critical traffic.

⚙️ How does TSN guarantee predictable latency?

Standard Ethernet with QoS priorities moves critical frames to the front of the queue, but gives no hard guarantee. A high-priority frame still has to wait if a maximum-size frame of 1,522 bytes has just started transmitting. That takes about 12.3 µs at 1 Gbit/s and about 123 µs at 100 Mbit/s, per switch. Under congestion, queues also build up, causing jitter.

TSN tackles this in three steps:

• Common time - through 802.1AS all devices share the same time with sub-microsecond accuracy. See also PTP.
• Time windows - the time-aware shaper opens and closes queues according to a fixed schedule (the gate control list). In the window reserved for critical traffic nothing else may transmit; a guard band ensures no frame is still half-way through when the window opens.
• Preemption - instead of a large guard band, the switch interrupts a low-priority frame in progress, sends the critical frame and then resumes the remainder. A fragment is at least 64 bytes, which cuts the worst-case waiting time at 1 Gbit/s from just over 12 µs to roughly 1 µs.

The result is deterministic behaviour: the latency of a scheduled stream can be calculated in advance and does not change when someone copies a large file over the same network. Typical industrial cycle times range from a few hundred microseconds to a few milliseconds.

🧱 What is IEC/IEEE 60802 and why is a profile needed?

The TSN family offers so many options that two “TSN-capable” devices do not automatically work together. A profile therefore specifies which functions, default values and configuration methods are mandatory for a given application domain:

IEC/IEEE 60802 is a joint project of IEC SC65C/WG18 and IEEE 802. IEEE approved the standard in March 2026, following the IEC vote in May 2025. The profile selects existing TSN functions and specifies configuration through YANG models. Security of network management is covered as well, including secure device identity according to IEEE 802.1AR and NETCONF over TLS.

Avnu, the CC-Link Partner Association, ODVA, the OPC Foundation and PROFIBUS & PROFINET International are developing a single common conformance test plan based on 60802. This is meant to prevent each protocol organisation from certifying its own, mutually incompatible flavour of TSN.

🔄 How does TSN relate to PROFINET, EtherCAT and OPC UA FX?

TSN handles transport at layer 2. Industrial protocols on top decide which data is exchanged:

• ProfiNET over TSN - conformance class D replaces the proprietary IRT mechanism with IEEE standards; PROFINET V2.5 supports IEC/IEEE 60802.
• OPC UA FX - uses OPC UA PubSub over UDP and follows 60802 where guaranteed latency is needed.
• CC-Link IE TSN - the CLPA completed this specification in November 2018, one of the first industrial networks built on TSN.
• IP - ODVA is working on TSN support and takes part in the common test plan.
• EtherCAT - processes frames on the fly and is already highly deterministic; TSN is mainly seen there as a backbone between EtherCAT segments, not as a replacement.

Older fieldbuses such as Profibus and DeviceNet will not disappear overnight. In existing plants (brownfield) coexistence is the norm; TSN is introduced mainly on new machines and lines.

🏭 Where is TSN used?

• Motion control and robotics - synchronised servo axes and robots communicating over the same network as the PLC
• Controller-to-controller - vendor-independent coupling between PLCs from different brands via OPC UA FX
• Machine vision - camera images from vision systems alongside control traffic, without the control loop stalling
• Automotive - in-vehicle networks for sensors and driver-assistance systems (802.1DG)
• Telecoms - fronthaul between antennas and baseband units (802.1CM)
• 5G - since 3GPP Release 16 a 5G system can act as a single logical TSN bridge, with translator functions on the device and network side

🛠️ How do you approach a TSN project?

1. Inventory the streams - which data is time-critical, with what cycle time, maximum latency and size? Distinguish scheduled traffic, reserved traffic and best effort, such as SCADA and MES communication or OPC UA client/server traffic.
2. Choose the profile and protocol - follow IEC/IEEE 60802 and pick the protocol (PROFINET, OPC UA FX, CC-Link IE TSN) that matches your PLC vendor.
3. Select hardware - use industrial switches and end devices that support the required TSN functions in hardware; an ordinary managed switch with VLANs and QoS is not enough.
4. Set up configuration - 802.1Qcc defines three models: fully distributed, centralised network with distributed users, and fully centralised with a Centralized Network Configuration (CNC) and Centralized User Configuration (CUC).
5. Design redundancy - where needed, combine 802.1CB with existing redundancy concepts such as PRP or HSR.
6. Test and monitor - measure latency and jitter under full load and include time synchronisation in your network monitoring.

🔐 What does TSN mean for OT security?

TSN is a reliability mechanism, not a security control. Convergence also has a downside: when IT and OT traffic share the same switches, physical separation disappears. Pay attention to the following:

• Segmentation is still required - TSN does not replace network segmentation into zones and conduits according to IEC 62443.
• Time is an attack target - anyone who manipulates 802.1AS messages can disrupt the entire schedule; protect the grandmaster and restrict who may send timing messages.
• Per-stream policing - 802.1Qci limits the damage from a device that sends too much traffic, whether deliberately or through a fault.
• Secure management - use secure device identity, 802.1X on access ports and encrypted management, in line with the security provisions of 60802.

❓ Frequently asked questions

Is TSN a replacement for PROFINET or EtherNet/IP?

No, TSN is a transport layer of IEEE 802.1 standards, not a complete industrial protocol. PROFINET, EtherNet/IP, CC-Link IE TSN and OPC UA FX run on top of TSN and use it to obtain guaranteed latency. As a result, different protocols can share the same TSN network.

Do I need special switches for TSN?

Yes, TSN functions such as the time-aware shaper, frame preemption and 802.1AS time synchronisation must be built into the hardware of switches and end devices. An ordinary managed switch with VLANs and priorities gives precedence, but no guaranteed, bounded latency. Choose TSN switches that support the IEC/IEEE 60802 profile.

What is the difference between TSN and ordinary QoS?

Ordinary QoS (802.1p priorities) puts critical frames at the front of the queue, but a frame already being transmitted or a full queue can still cause delay. TSN adds a shared clock, fixed time windows and preemption, so the latency of scheduled traffic can be calculated in advance. QoS gives priority; TSN gives guarantees.

Does TSN also work wirelessly?

TSN was designed for wired Ethernet, but from Release 16 onwards 3GPP has specified how a 5G system can behave as a logical TSN bridge. Wireless TSN variants for Wi-Fi are still being researched. In practice, wired TSN remains the norm for hard real-time applications.

When was IEC/IEEE 60802 published?

The industrial TSN profile IEC/IEEE 60802 was published as edition 1.0 on 29 June 2026, after IEEE approved the standard in March 2026. The profile defines which TSN functions industrial devices must support. A common conformance test plan from organisations including PI, ODVA and the OPC Foundation builds on it.

Does TSN make an OT network more secure?

TSN makes a network more reliable and predictable, but not automatically more secure. Functions such as 802.1Qci do limit the impact of a device that sends too much traffic. Segmentation, access control and monitoring according to IEC 62443 remain necessary.

📌 In summary

TSN turns standard Ethernet into a network with predictable timing through a shared clock (802.1AS), time windows (802.1Qbv), preemption (802.1Qbu/802.3br) and redundancy (802.1CB). With the IEC/IEEE 60802 profile from 2026 there is a common foundation for industrial devices, on which PROFINET, OPC UA FX and CC-Link IE TSN build. For OT convergence, TSN is an important building block, provided segmentation and security are designed just as carefully.

TSN gives Ethernet bounded, predictable latency, so that real-time OT traffic and ordinary IT traffic can safely share the same network.