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The communication delay uncertainty of Ethernet has become a major obstacle in application on industrial control. To solve the problem, it's very important to exactly model and carry out quantitative research on the real-time performance of Ethernet. This paper proposes a new solution to accomplish the modeling of Ethernet based on CSMA/CD media access method and Binary Exponential Back-up algorithm, especially giving the accurate calculation formula of the net collisions adopting the multiple integrals method. On the basis of this model, some evaluation indexes including collision probability, failure probability and average time for a failure are selected to complete the quantitative analysis on Ethernet with different number of stations. Moreover, the paper comparatively studies the influence of the different network parameters on the Ethernet real-time performance. Finally, the correctness of the mathematical model is verified by the MATLAB simulation.

Network calculus has been a widely used theory for the performance analysis of network, especially switched Ethernet. The delay is the most important factor affecting the performance of Ethernet. In this paper, we get the arrival curve and service curve of the switch of each level. And then we derive the recurrence formula between the maximum delay and network scale using the theory of network calculus. After building the tree topology model of Ethernet/SDARP, which is service robots communication protocol based on switched Ethernet, we calculate its delay by the formula. The simulation result by OPNET proves the accuracy of the formula. It also demonstrates the expansibility of the protocol.