In order to understand accurately and use correctly cai in teaching practice , based on the theory of modern education , the author in the essay explains the strong points and weak points of cm , and focuses on analysing some problems for misusage of cai 摘要为了在教学实践中正确认识并合理使用计算机辅助教学，文章结合现代教育理论，阐述了计算机辅助教学的优势及局限性，着重分析了计算机辅助教学在应用中的一些误区。
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We do research on the transitions between states of network protocol , the protocol misusage detection model based on markov chain , the framework of the ids technology and protocol anormity after we discuss the current technology . the main research contents of this paper include : research on transitions between states of network protocol and session process , protocol misuage and the anomaly detection model based on markov chain , the research of intrusion detection framework , more accurately model based on the characteristic of the network traffic and so on 在分析了现有入侵检测系统的基础上,本文围绕典型网络协议状态转换、基于马尔可夫链的检测模型、入侵检测技术框架、以及协议异常等几个方面展开深入研究,主要工作内容包括:典型网络协议转换状态的分析和会话过程的研究;基于马尔可夫链的网络异常检测模型;分布式的检测架构;针对网络流量特征而提出了精确的检测模型等。
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Then , the paper present a protocol misusage ids in application layer based on markov chain , and obtain the following results after test : the system can have good effection on detecting the probe packet , dos attack and novelty attack . the system can overcome part of disadvantages in traditional intrusion detection system , and adapt requirements with different network . the experiment shows that the system can improve the detection accuracy rate , reduce the false negatives probability 通过对检测系统的测试分析,系统对扫描探测报文、 dos攻击报文和新的攻击报文等有较好的检测率。基于马尔可夫链建立的网络异常检测系统可以克服传统入侵检测系统的部分缺陷,能够适应不同网络环境的要求,同时也有效提高了系统的检测能力和检测效率,降低了误报率。
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First of all , this paper introduce the markov chain theory . after analying the specifications of http , smtp , ftp , telnet and tcp , we know the tcp session is fit for the markov process . in this paper , we analyze the transitions between states of the application layer with the normal tcp traffic , and build a protocol misusage detection model with the normal traffic in darpa data set 本文采用了马尔可夫链理论,仔细分析了tcp协议规范,并研究分析了典型网络应用层协议http 、 smtp 、 ftp以及telnet ,验证了基于tcp协议的会话过程就是一个马尔可夫过程。
