Time Sensitive Networking (TSN)

TSN provides fully deterministic real-time communication over Ethernet. Ethernet is widely used and growing in popularity because it’s low-cost, well standardized and easily accessible. It is also scalable and offers a wide range of bandwidth.

However, regular Ethernet is not enough for many systems, because they require real-time and safety-critical communication. This includes industrial automation, where machines must share their data for synchronization, control, analysis and optimization. The same goes for energy production, where networking is needed for example for substation connectivity. Reliable communication is also necessary in automotive industry especially now that vehicles are becoming more and more automatized. Regular Ethernet does not fulfil the real-time communication requirements of these systems, because they need certainty about the communication latency times.

Time Sensitive Networking is the solution: it guarantees the communication latency times. Also network redundancy is often needed and most notable of the current redundancy protocols are IEEE 802.1CB and High-availability Seamless Redundancy (HSR). They provide redundancy with no single point of failure and zero time to recovery in case of a failure. The network is fully operational even during maintenance, as any device can be disconnected and replaced without breaking the network connectivity.

Because of TSN and redundancy protocols Ethernet becomes very attractive option for systems requiring real-time and safety-critical communication. Indeed, the usage of Ethernet is rapidly increasing in automotive, industrial automation and energy production. Ethernet and TSN will play a key role in the Industrial IoT and Industry 4.0. As machines and devices become connected, data will be more easily accessible – those who don’t take advantage of it will be left behind.


Traffic Policing and Shaping

TSN is a set of IEEE 802 sub-standards and guarantees communication latency times with several different methods. Traffic policing and shaping combined with resource reservation are some of these methods. In traffic policing and shaping, traffic bandwidth is measured and if it exceeds the configured rate, actions are taken to force the rate back to where it should be. Traffic shaper can delay frames while policer simply drops the excess traffic.

Traffic policer provides means for limiting the rate of incoming data stream(s) by dropping frames exceeding the configured rate. The policer needs to know the frame length to compare if it fits with the configured traffic rate.

Traffic shaper limits the transmit rate to comply with configured maximum allowed transmit rate. Shaping consumes more hardware resources than policing because it requires buffering the frames. Frames that exceed the configured rate are delayed increasing the latency they experience. The rate at which frames can be transmitted from certain priority queue can be configured, so traffic shaping can affect in which order the priority queues are emptied. Also shaper may drop the frames if buffers are full.


TTTech offers several TSN IP options for FPGA & ASIC, please find out more information here: https://www.tttech-industrial.com/products/slate/