Figure 1: TSN standards define layer 2 functions and can coexist with various APIs. Image source: Texas Instruments
some of the many IEEE 802.1 standards for implementing TSN, considers how IEC/IEEE 60802 relates to TSN, and compares TSN with other protocols like EtherCAT, ProfiNet, and EtherNet/IP. It then presents MPUs from Texas Instruments, NXP, and Renesas that include TSN capability, along with development platforms that support the integration of deterministic networking into Industry 4.0 devices. Prior to the development of TSN, real-time networking was only available on specialized industrial field buses. Field buses are often referred to as the ‘industrial Ethernet’. The 802.1 TSN standards define layer-2 functions and local area networking (LAN) level switching and add the concepts of time and synchronization. TSN does not replace protocols at levels above layer-2 and does not define the software interface or hardware configurations and features, making it compatible with various application programming interfaces (APIs) (Figure 1). Existing TSN traffic shaping algorithms enable the co-existence of real-time traffic with regular best-effort traffic within standard Ethernet networks. Determinism and low latency can be guaranteed for time-critical communication. That can support the deployment of safety-related systems in industrial
How to implement Time Sensitive Networking to ensure deterministic communication
and automotive environments. Some of the key IEEE 802.1 TSN sub-standards include (Table 1): ■ IEEE 802.1 AS – timing & synchronization ■ IEEE 802.1Qbv – time-aware shaper ■ IEEE 802.3Qbr – interspersed express traffic ■ IEEE 802.1Qbu – frame preemption ■ IEEE 802.1Qca – path control & reservation ■ IEEE 802.1CB – redundancy ■ IEEE 802.1 Qcc – enhancements and improvements for stream reservation ■ IEEE 802.1 Qch – cyclic queuing & forwarding ■ IEEE 802.1Qci – per-stream filtering and policing ■ IEEE 802.1CM – time-sensitive network for fronthaul
standards that are required to ensure the operation of TSN. Time synchronization is the bedrock to ensure the synchronization of clocks across a network. 802.1AS, also called 802.1ASrev, is the primary sub-standard related to synchronization. Another group of sub-standards relates to bounded low latency. Support for bounded low latency is a necessary condition for achieving determinism in data transmissions and is defined with five sub- standards: 802.1Qat (credit-based shaper), 802.3Qbr (interspersed express traffic), 802.1Qbu (frame preemption), 802.1Qbv (time aware shaper (TAS)), 802.1Qav (cyclic queuing and forwarding), and 802.1Qcr (asynchronous traffic shaping). Ultra-reliability is required to deal with faults, errors, and provide redundancy and related functions.
Deterministic communication is vital in various applications such as autonomous robotics and other Industry 4.0 systems, 5G communications, automotive advanced driver assistance systems (ADAS), and real-time streaming services. The IEEE 802 Ethernet standards, called Time Sensitive Networking (TSN), have been expanded to support deterministic communication. Properly implemented, TSN can be interoperable with non-TSN devices, but deterministic communication is only available between TSN- enabled devices. There are
numerous IEEE 802 standards to coordinate when implementing TSN and ensure that it delivers both deterministic communication and interoperability, making it complex and time-consuming to design TSN into networking equipment from scratch. Instead, designers of networking equipment can turn to microprocessor units (MPUs) with built-in TSN functionality to speed time to market and reduce development risks. This article reviews the basics of TSN operation and implementation, introduces
Written by Jeff Shepard
IEEE TSN can be partitioned into four categories of sub-
we get technical
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