Design And Implementation Of Computer Network Virtual Experiment System Based On Dynamips

With the development of information technology, people could learn more courses conveniently through distance learning. But the teaching effects of experimental courses in distance education are not very good due to the experimental sites, experimental equipments and other factors. With the help of virtualization technology, the teaching effects of experimental courses in distance education could become better and better. In this paper, relying on the teaching reform item of computer network management and practice, we analyze Dynamips, the virtual technology of the router’s hardware,and have a secondary development on it after analysis of the classification as well as pros and cons of the domestic and foreign research of computer network virtual experiment system.Especially,we design the virtual experiment system of computer network courses through taking advantage of LAMP and RIA technology.With the help of the virtual experiment system, users could learn experiment online and interact with the virtual network device.Then the problem of the poor simulation results of the virtual network devices are solved and the learning of experiment become easier. So the system has some practical value in teaching and research.1. We regard Dynamips as virtual simulation core of experiment system in order to solve the problem of the poor simulation results of the traditional virtual experiment of computer network.Through studying the source code of Dynamips, the way which the interface of Dynamips is applied to set up a virtual network and remote interaction, is determined. A selection algorithm which is optimal to the idle indicators of virtual machine is fixed on the phenomenon that virtual machine occupies host machine greatly. We find that the idle-pc value is optimal after test. In other words, we can reduce the CPU usage of the virtual machine greatly in this way.2. In order to improve the convenience of Dynamips and the generality of the system, the decision-making of a kind of web application program on technology selection is put forward and it is used in this system. LAMP technology is used in the system architecture according to design goal and need of the system. Furthermore, RIA is used to improve function extension in network topology presentation of Dynamips and its remote connection.The function module of the system and the corresponding database are designed in detail.3. In order to ensure the security and convenience of system authentication, the digest authentication which relys on Ajax of image verification code is used.With the help of PHP function,the image verification codes which can interfere with violent attacks of the illegal program are produced dynamically. The users’ messages are transmitted in the form of ciphertext by using abstract function. The authentication process becomes safe and achieves seamless connection through combining with Ajax.4. Dynamips can not generate the network topology interface in traditional system.In this study,with the help of Flex3.0technology,the virtual machine’s connection information which is in the format of XML is read dynamically in the way of URLLoader and a network experiment topology is generated in the browser. And users not only see experiment topology but also operate the virtual devices in it.5. With the help of RIA’s Applet technology, the Telnet client basing on http could connect with Dynamips remotely. In this way, we solve the problem that the system can not be cross-platform due to relying on OS Telnet client and make Telnet client basing on http interact dynamically. At last, the sandbox model constraint of Telnet client is solved by digital signature.