What is TSN?

Time-Sensitive Networking is an extension of standard Ethernet with the primary goal of making standard Ethernet deterministic. This allows technicians to precisely understand the exact time it takes for traffic to travel through the network, as well as the nature of any delays and transmission time variations (jitter) that traffic will experience.

Conventional internet applications have a much higher tolerance for latency and jitter than many industrial processes can tolerate. Because Ethernet inherently lacks the ability to guarantee the timing of events, it cannot be reliably used in many machine applications, and this lack of determinism can lead to quality degradation or even machine damage.

Various open protocols, such as CC-Link IE, have been adopted to address these issues, and when combined with TSN, they continue to provide valuable capabilities for industrial applications. While these protocols provide a method for deterministic Ethernet for industrial applications, enabling what is now known as Industrial Ethernet, they still fall short of providing a well-defined converged solution. The current trend toward TSN will ultimately address this gap. However, it is important to remember that TSN is simply a "plumbing" that transmits data from one location to another in a deterministic manner. It does not address higher-level application functions such as safety or motion control. Therefore, these protocols are still needed to implement these functions.

Another consideration for TSN networks is bandwidth. In addition to determinism, the standards behind TSN allow Industrial Ethernet to more efficiently utilize this typically fixed resource. Prioritization capabilities allocate the necessary bandwidth, ensuring that all traffic flows smoothly on the network and preventing less important data from interfering with higher-priority data.

What standards are involved in TSN?

The IEEE 802.1 Ethernet specification defines how the technology delivers deterministic performance and ultimately convergence by implementing features such as time synchronization and traffic prioritization.
IEEE 802.1Qbv allows for the definition of transmission time slots for network traffic queues. This controls when each traffic type can access the network. In this example, four time slots are divided among eight queues. Within each time slot, the higher-numbered queue has priority.
IEEE 802.1AS – Timing and Synchronization for Time-Sensitive Applications: Time synchronization provides the foundation for determinism by ensuring that all devices on the network share the same sense of time. For example, if it is 10:00 AM, all devices on the network know this and their operations are synchronized to the same clock. This minimizes the possibility of time drift that can cause delays and variations in data transmission (latency and jitter), thereby enabling the timely and predictable delivery of critical data traffic.
IEEE 802.1Qbv – Enhancements for Scheduling Traffic

How are TSN standards evolving?

Like any technology, the IEEE 802.1 standard that defines TSN is constantly evolving, with existing standards being refined and new ones emerging all the time. Even as the standards evolve, the technology itself is mature enough to be implemented in projects. Evolving technology can be considered more valuable because it continues to evolve to meet current needs and is therefore less likely to become obsolete. Therefore, this development is positive.

In contrast to this evolution, the Ethernet standard has a long track record of backward compatibility. Ethernet technology has been around for approximately four decades, yet in many cases, older equipment is generally compatible with newer equipment. TSN is expected to follow this trend. Therefore, companies that need to complete projects immediately can incorporate TSN now, confident that it is unlikely to become obsolete in a few years. There is no need to wait for TSN to be "ready" at some uncertain future point, which is unlikely to ever arrive.