Design And Implementation Of Fault-tolerance For NOP Protocol

NOP(Node Order Protocol) is a communication protocol designed for small safety critical real-time system. This protocol is developed based on safety concept and analyzing the shortcomings of current design principle of communication protocol. Its key features are:(1) The sequence for nodes to access the shared media is predefined, and all nodes must agree on the sequence before communicating. And communication is triggered only by events without global time concept.(2) NOP haspredictability and flexibility.(3) NOP has greater network utilization.(4) The safety concept is involved in the entire lifecycle of NOP.In the thesis, the fault-tolerant mechanism TMR+1is introducedto NOP, it implementsastrongerfault-tolerant protocol NOP V2.0. The main work of the thesis includes design of fault-tolerance, formal verification of design and implementation.In the design and implementation of NOP V2.0, the safety concept is involved.The design is guidedby IEC61508. And semi-formal method FMEA is adopted to statically systematically analyze failure mode of the system, beyond that, formal verification method SPIN is adopt to dynamically simulate protocol behavior, and then verify the correctness of the protocol by exhaustively searching the state space of the protocol.The state space reduction method is utilized to reduce the occupied resource in verification process.And the verification result shows that the protocol have expected behaviors. Finally, the thesis implements the design. The wireshark tool is used to analyze communication behaviors of the protocol. The results show that fault coverage requirement is satisfied in communication behaviors.