Fault tolerance of multihoming in FL-net for nuclear instrument and control environment

We propose multihoming, the token synchronization, and the packet selection in FL-net to achieve fault tolerance. Multihoming assigns two IPs on two interfaces which reach two disjoint paths so that 1 + 1 packets in FL-net for the 1 + 1 protection architecture are supported. However, based on the architecture, a problem called delay mismatch makes FL-net nondeterministic because of collisions. To solve the delay mismatch problem, the packet selection selects the early packet between 1 + 1 packets and then the token synchronization ensures the time to send both of 1 + 1 packets is after the time to receive both of them. This synchronized sending time not only avoids collisions but also matches delay and token cycle time on two disjoint paths. Therefore, fault tolerance on two disjoint paths is achieved. NS2 simulation results are shown in two scenarios. One scenario indicates matched token cycle time and another scenario indicates our method achieves fault tolerance in queueing delay, queueing delay variance, and throughput.