Motion control needs packets that arrive on time every time, while video, file transfers and IT data want to share the same cables. A set of IEEE Ethernet extensions now lets both kinds of traffic coexist without the real time data ever waiting in line.
Standard Ethernet delivers packets eventually, but not at a guaranteed time. TSN adds shared clocks, scheduled transmission and redundancy so control traffic gets bounded, predictable latency on converged networks.
What Is Time Sensitive Networking?
Time sensitive networking, or TSN, is a family of IEEE 802.1 standards that add precise time synchronisation, scheduled traffic, frame preemption and redundancy to standard Ethernet, giving guaranteed low latency for critical data. It lets protocols such as PROFINET share a network with IT traffic.
IIoT World reports more than 3800 TSN capable products from over 700 vendors. PROFINET, EtherNet/IP and CC Link can run together on one converged network.
Before TSN, hard real time needed special hardware, as in EtherCAT or PROFINET IRT. TSN moves those capabilities into standard switches.
The CC Link Partner Association has been integrating TSN since 2018, and OPC UA over TSN is aimed at controller to controller communication.
5 Powerful TSN Standards
Every switch and device shares one clock through 802.1AS, often to better than a microsecond. The schedule in 802.1Qbv then opens time slots reserved for control traffic.
Frame preemption lets an urgent frame interrupt a long best effort frame, then resume it. This cuts waiting time on slower links.
How Scheduled Traffic Works
Switches become central to the design, so choose ones listed for TSN and industrial use, see network switches for SCADA and DCS.
For higher layers, OPC UA PubSub over TSN gives a vendor neutral way to exchange real time data.
TSN vs Standard Ethernet
| Feature | Standard Ethernet | With TSN |
|---|---|---|
| Latency | Variable | Bounded and predictable |
| Time sync | Optional, loose | Built in, sub microsecond |
| Traffic mix | Best effort | Scheduled plus best effort |
| Redundancy | Ring protocols with recovery time | Seamless with 802.1CB |
| Vendor lock in | Low | Low, based on IEEE standards |
The IEC and IEEE 60802 joint profile selects TSN features for industrial automation. It aims to make devices from different vendors interoperate.
Seamless redundancy complements ring designs described in DCS network redundancy.
Latency Estimate
Path latency ≈ Hops × (Frame time + Switch latency)
Example, 128 byte frame at 100 Mbit per s:
Frame time = 148 × 8 ÷ 100 = 11.84 µs
5 hops, switch latency 3 µs
Latency ≈ 5 × 14.84 ≈ 74.2 µs
At 1 Gbit per s the same frame takes only 1.18 µs per hop. With TSN scheduling, this figure becomes a guaranteed bound instead of a best case.
Link speed and cabling limits are covered in Ethernet cable types and lengths.
Where TSN Is Used
Most plants adopt time sensitive networking gradually, starting with new machine cells and backbone switches. Legacy devices keep working as best effort traffic while new ones use scheduled streams.
Latency Calculator
Compare the path latency with your control cycle time. A good rule is to keep it well under half the cycle.
- One converged network for OT and IT.
- Guaranteed latency for control.
- Standard IEEE technology.
- Seamless redundancy options.
- Needs TSN capable switches.
- Schedules require careful configuration.
- Profiles still maturing.
- Mixed legacy devices.
Think about TSN at the architecture stage, alongside the layers in the ISA 95 automation pyramid.
TSN for Industrial Automation Survey PDF
Deterministic Communications Video
Time Sensitive Networking FAQ
Related Articles
- PROFINET Communication Guide
- EtherNet/IP vs EtherCAT
- OPC UA Explained
- Network Switches for SCADA and DCS
- Network Speed and Throughput
External References
- TSN for Industrial Automation, ACM Computing Surveys
- How TSN Transforms Automation, IIoT World
- TSN, Wikipedia
What We Learn Today
- Time sensitive networking adds sync, scheduling and redundancy to Ethernet.
- 802.1AS, 802.1Qbv and 802.1CB are the core building blocks.
- Converged networks carry control and IT traffic with bounded latency.