LAN Environment Experiment System Design And Implement Based On Three Layers Architecture

In the field of computer network, LAN is a hotspot, but in the teaching process of computer network, teaching purpose which is about LAN don't achieve completely. The cause is a lack of experiment equipment. As a result, the student cann't grasp the base knowledge of computer network.As a solution, a kind of simulator software is appear, it's Network Simulator. We can simulate network environment, simulate process of build network, simulate the process of network equipment choice and configuration, simulate network logic topology map etc. It can reduce cost of teaching and improve the practiacl ability of students. But a lot of Network Simulator is designed to some specifical manufacturer and some speciafical mode of network equipment at present. So they are limited, complex configurraion, and a lack of base knowledge of network.We can design a Network Simulator which accord with teaching request of computer specialty in high school, through analyse the present other Network Simulators'advantage. It's"The Experiment System of LAN Environment"in this paper.In the process of description of the design of"The Experiment System of LAN Environment", introduce the"three layer architecture of software development"and the process of design with it. At first, introduce the definition of architecture and its'trait, and then descrip the method of sign with"three layer architecture", at last, realize"Three Layers Architecture"in the experiment system of LAN environment. By the way, the data access layer is made of XML file, it brings the advantage. The Three Layers Architecture is descriped as follow:The first layer: User Layer. It intercommunicates with the user. It can accept the users'input and trim them to obtain logical input parameters, and drive the function of lower layer to accomplish the users'request.The second layer: Business Logic Layer. It deal with all data from the data layer or the user layer. It depends on the operation regular, the operation flow, the operation request. It depends on the operation logical. It is the important layer in the architecture, as it acts two roles. It transfers the lower layer and at the same time it is transferred by upper layer. All relations associate it. In the current system, the business logic layer is to accomplish the jobs, as network equipment parameters configuration, CLI treating, building LAN logic topology, performance estimating, network fulx analysis.The third layer: Data Access and Defination Layer. It's use is define and access the data. In this paper, this layer is define the struction of XML file and how access the XML document, include the operation: SELECT,INSERT, UPDATE, DELETE,etc.In the system, this layer's task is recording users'solution to every network equipment configuration and LAN topology map.The Three Layers Architecture is better than The Two Layers Architecture or The Single Layer Architecture. The Three Layers Architecture is adapt to colony development, everyone have owner work, and it improve the efficiency. In the development of The Two Layers Architecture or The Single Layer Architecture, everyone has to grasp the whole system. But in the development of The Three Layers Architecture, only a little of person have to grasp the whole system, it reduce the difficulty of the development. The most advantage is security with The Three Layers Architecture, it can reduce the entry, avoid dangerous system function. At last, The Three Layers Architecture can reduce maintenance time.By one year time, achieve the anticipative aim. The Experiment System of LAN Environment take on the network equipment lieing function, network equipment parameter configuring function, network logic topology maping function etc. But the advanced function only designed, cann't achieve. The advanced functions are auto judge performance bottleneck function and auto optimize the network logic topology function. They are depend on the network flow mode later.