Time Sensitive Networking (TSN) is a collection of industry standards that extends conventional Ethernet with various procedures and protocols. The idea is to avoid delays or losses in data transmission and thus guarantee high reliability – especially when the network load is high. For the cabin, for example, TSN enables a shared network. One example is the Passenger Announcement System, which is only allowed to transmit with minimal delay to avoid echo effects and thus ensure easily understandable voice transmission. This is particularly relevant when it comes to passenger safety announcements. Data traffic is therefore prioritized.
Consequently, there is data that is more important than others and the experts transfer this to the network. The aim is to guarantee that this data arrives in any case (determinism). This means, for example, that it is sent over different paths, even if a cable breaks or a device malfunctions. Another advantage is that TSN enables programmers to ensure that the data arrives within a certain time. With conventional Ethernet, it is not possible to maintain such precise time synchronization. TSN enables this not only in milliseconds but microseconds – again, particularly relevant for safety-critical systems and thus the safety of passengers. Another example: If a passenger is watching a movie via in-flight entertainment, this data transmission is of lower priority than the data from a smoke detector in the event of a fire. The latter data packet must be allowed to “drive” preferentially through the data network via TSN like an ambulance with blue lights on the highway. Of course, one could use an extra cable per data stream to achieve the same result, but this is expensive, consumes space on the aircraft, and adds weight. Therefore, it is more efficient to use one cable for different purposes at the same time. This means prioritizing the data packets differently.
The TSN experts at ZAL GmbH ensure that it is known in advance which devices send the maximum number of bits per second. With the help of per-stream filtering and policing, they control what is allowed to pass through the network and ensure that it arrives, like a data police. To do this, they examine and design the topology, i.e. the network participants and devices as well as their connections to each other. In addition, they work with streams, with which one can trace from which device, and which amount of data traffic goes where. In addition, the constraints define what must arrive when and with what reliability, i.e. whether there may be losses or not. Finally, this data can be used in a program that calculates the rules that must apply in the network The team has developed a tool for this purpose that can be used to automatically generate multiple-use paths through the network, based on the aforementioned topology and streams. It thus ensures that no end device exceeds its share of the available data bandwidth in the network that is scheduled for the device. Accordingly, TSN is a set of security measures that the experts take to be able to certifiably guarantee at the end that this data arrives safely in a given time.
Since 2019, the experts of ZAL GmbH have been testing TSN in several projects such as DELIA (https://zal.aero/news/verknuepft-verbunden-vernetzt-neues-vom-forschungsprojekt-delia/) or the ZAL Endpoint (https://zal.aero/news/indika-und-der-zal-endpoint-viel-digitalisierung-auf-kleinster-flaeche/). They advise partners on the sub-standards relevant for their use case and check which switches (TSN devices) are suitable. They develop network configurations to achieve the goals that are placed on the Ethernet network depending on the project. In the next step, they will implement TSN in the cabin demonstrator at ZAL GmbH.
Do you find TSN exciting and want to learn more? Call us, we are looking forward to it!
Jens Neumann
Development Engineer Data & Power Networks
+49 40 248 595-133
