The Design And Implementation Of NOP Protocol Based On UIO

Nowadays, with the flourishing development of research on the computer technology since last century, more and more computer systems are used in safety-critical field. And the systems which serve critical area related to the safety of the people, public property and resources-environment safeties, have been named as the safety critical system. With the increasing functions, the safety critical system has appeared the typical distribution characteristics gradually. For this reason, the communications between its subsystems have become a core component of the modern distributed safety-critical network. As a new safety-critical real-time communication protocol, NOP builds a distributed system on the concept of the node order under the safety framework of IEC61508, eliminating the dependence of communication protocol to the global clock, and sets up transmission semantics of time-triggered protocol which is achieved by event-triggered mode depending on the node order. NOP provides a method to solve the shortcomings of poor predictability for the traditional event-triggered (ET) network and low flexibility for the time-triggered (TT) network. Combining the advantages of both TT network and ET network, NOP gives an orderly and reliable way for the realization of safety critical system.In this paper, in order to ensure that the NOP protocol can work in Linux user space, the Userspace I/O(UIO) framework is used to build a Communication Network Interface (CNI) for the NOP protocol. Meanwhile, the NOP protocol has been implemented base on the communication primitives in the user space. And it makes the NOP protocol as a separated module to control and communicate with the network. In addition, the performance evaluation for the existed protocols has been done, and the experiments show that the NOP protocol has low delay and high efficient utilization of network resources. So with new design ideas and concepts, NOP protocol has a great advantage to replace the traditional time-triggered protocol which has low resource utilization and poor flexibility in some cases.