ReT-FTS: Re-transmission-based fault-tolerant scheduling in TSN

Abstract

Time-Sensitive Networking (TSN) has become a popular technique for providing deterministic transmission policies in the modern Internet of Things (IoT). To simplify configuration complexity and enhance dynamic and flexible behavior in TSN, IEEE 802.1Qch (Cyclic Queuing and Forwarding, CQF) was released. However, messages may encounter transient faults during transmissions, which can influence schedulability and reliability. To protect against such faults, re-transmitting incorrectly received messages is a common approach. However, unlimited re-transmissions can cause a temporary and rapid increase in network load, leading to situations where some streams cannot be transmitted within their deadlines, decreasing the reliability of time-critical streams. This presents a new challenge for performing re-transmissions in TSN. In this paper, we address this issue and present a re-transmission-based fault-tolerant scheduling technique for TSN (called ReT-FTS). Each stream is limited to a minimum number of re-transmissions while maintaining reliability requirements. Therefore, we develop analysis techniques for quantifying network reliability in various scenarios, including those in which streams are dropped or not dropped. We then demonstrate that the reliability does not increase when streams are dropped. We also conduct extensive experiments with synthetic and realistic networks in order to demonstrate the effectiveness of our approach.