Challenges and Limitations of IEEE 802.1CB-2017

For many Ethernet-based real-time systems, such as those from automotive, avionics, and industry automation domains, fault tolerance is emerged as an essential requirement for enabling fail-safe or fail-operational behavior. Consequently, the IEEE 802.1CB-2017 standard was published. It is currently the only available time-sensitive networking group standard offering protection against transmission errors. It tackles these faults by preventively replicating the frames and transmitting redundant copies via different paths to the destination. However, in contrast to its obvious advantages, the standard contains some pitfalls: most notably, it lacks protection mechanisms against inadequate configurations, which can not only invalidate the intended increase in reliability but even actively jeopardize the safety of the network. Due to the lack of alternative mechanisms, it is crucial to fully understand the fundamental properties of the standard and its implications on the safety aspects of the network traffic. In this letter, we identify critical aspects and limitations of the standard. We demonstrate the risks of inadequate configurations, discuss their ramifications. Finally, we provide an intuition and initial steps toward deriving the formal worst-case timing analysis of the standard, which is a key requirement for its safe and efficient implementation in the aforementioned real-time domains.