The Reseach And Application Of Computer Network Performance Evaluation Based On Petri Nets

Petri Nets is widely applied in simulation and analysis discrete event systems because of the simple, intuitionistic and the strong power of simulation. It has main characteristics, such as, parallel, nondetermination, asynchronism and the power of distributing and analysis. Liveness, boundness (always call N-safeness), home-state and justice are some basis properties of Petri Nets. Since the concept of Petri nets was putted forward, the research of the nature extremely is active.Along with the computer science and the technical development, the computer application and the computer network is unceasingly popular. More and more people feel that the computer network system performance appraisal is importance in the society technology advancement. The computer network performance evaluation research goal mainly is choice, improvement and design of the model. The performance evaluation method approximately may be divided into two kinds: measuring technique and model method. But the model method has more advantage than the measuring technique. In the tradition performance analysis method the queuing theory is used to solve the system description problem. It's mathematic foundation is Markov chain. At the beginning of the 80's, stochastic Petri net has provided a new mathematics description tool for the system performance analysis. Lin Chuang, Qinghua University Professor, his research has most the representation.The model method is used in the paper. Computer network performance is evaluated by the P/T net, the colored net and the cyber net in the paper. The research of the paper is made of analysis, simulation and verification. The model is designed by combining application environment with careful research. Afterwards, the model is revised and consummated by constitutive property analysis and simplification technology. Finally, the verification is given by the invariable technology and the characteristic of main behavior; To the actual problem processing result, some new conclusions are given. Main research is including below content:(1) The Sender-Receiver problem is a typical one in solving the sharing message channels. After analyzing the model and combining with the characteristics of Petri Nets and the system on Internet, this article presents a more practical model with expanded functionalities.(2) Through analyzing the selective repeat protocol, this paper describes a model based on a extended selective repeat protocol (ESRP). The model has used two kinds of repeatable retransmit technology. One is that the sender will retransmit all unacknowledged frames in order when time is out. The other is a negative and selective repeat protocol of following frame. The model of ESRP can guarantee the communication of the network timely and reliable. Finally the verification is given.(3) After analyzing the demand of elevator system, this paper presents a colored cyber net with a colored inhibitor arc. The model based on elevator system of thecolored cyber net is proposed finally.