Fault-Tolerant Cyclic Queuing and Forwarding with Fast ACK in Time-Sensitive Networking

TSN is widely used in industrial automation networks because it can provide deterministic transmission services for critical data. Cyclic Queuing and Forwarding (CQF) is used to shape critical data. However, unexpected data errors may occur due to transient failures like electromagnetic interference. IEEE 802.1CB provides a solution to tolerate such failures by transmitting multiple replicas of data over disjoint paths. However, this solution introduces network resources wastage. Compared to redundant transmission, retransmission can reduce resource waste, but may violate the determinism in TSN. To address this issue, we propose a fault-tolerant mechanism for CQF that supports retransmission, called fault-tolerant CQF (FT-CQF). FT-CQF adopts the Go-Back-N concept to resist failure. Therefore, it does not violate the original transmission sequence of frames. On the basis of standard CQF, FT-CQF occupies an additional queue to cache replicas of Time-Trigger (TT) flows and reserves time slots to forward them. FT-CQF will forward or remove these replicas based on the ACK information. Non-TT flows can use this time slot to transmit when replicas are removed. We implemented FT-CQF on OMNeT++ and verified the performance of FT-CQF. Simulation experiments show that FT-CQF is effective in terms of reliability, bandwidth consumption, and delay.