【作者】 黄敏；

【导师】 张小真；

【作者基本信息】 西南师范大学 ， 计算机应用技术， 2005， 硕士

【摘要】 互联网的高速发展,促使了网络教育等大批应用领域的产生,随着这些应用的不断深入发展,又对网络体系结构提出了更高的要求,如何保证用户所获得的服务质量成为当前研究的热点。当前国内外对服务质量的研究大多基于对网络体系结构和Web服务器进行修改,这些研究的成果目前未能得到广泛应用。 论文针对如何保证网络教学系统的服务质量这一问题进行了研究:硬件、软件和人员是网络教学环境的三大重要组成因素。而现有的网络教学服务质量评价体系并未考虑网络教学的硬件环境,在教学硬件环境中,影响教学服务质量的最主要的因素就是教学服务器性能和网络传输质量。教学服务器本身可能出现的过载和网络传输延迟都可能造成学习者长时间等待而无法获取请求的学习资源,主要原因有两点:一是由于Web服务器的过载导致http请求队列溢出,请求丢失,或者是服务器对用户请求响应速度太慢超过用户的忍耐时间:二是由于网络拥塞导致学习者请求的学习资源丢失或延迟。 针对以上问题,论文分析了当前从服务器硬件着手改善网络教学服务质量的方法,并指出了这些方法的不足。在此基础上,论文提出了一种网络教学资源变换方法:根据Web服务器的负载和用户的网络状况对用户的http请求对象进行变换,通过避免服务器的过载来提高用户所感知到的服务质量。论文所做的主要工作有:首先对服务质量的概念进行了研究,从广义的角度定义了论文中所用到的服务质量;然后根据系统检测到的Web服务器负载和用户的网络状况,对用户http请求的资源进行变换,变换的目的一是避免Web服务器的过载,二是使响应用户的学习资源在最大程度上适合在当前的网络状况下来传输。 论文的创新在于扩展了现有网络教学服务质量评价体系,将网络教学的硬更多还原

【Abstract】 With the rapid development of Internet, such application fields as Web-based education is appearing, whose increasingly further development has a higher request for the Internet structure, especially for the quality of service for the customer. In the present, most research of the quality of service in foreign countries and China bases on the improvement of the Internet structure and Web server. But those researches’ achievement cannot be applied in short term.The study of this paper according to the problem that the quality of web-based teaching and learning cannot be promised, it is found that hardware, software and people are indispensable to web-based teaching and learning. However, current critenons of quality of service in web-based teaching and learning haven’t taken hardware environment into account. The major factor to influence quality of service is the capability of the teaching server and the quality of the network transportation in teaching environment. There are two problems in teaching server itself: One is overloading, the other is the delay of network transportation, which makes learner wait for a longer time or cannot get the learning resources. What causes these problems is the following: first, the overloading of Web server leads to the overflow of the http request queue, or the speed in response to the customer’s request is so low that customers are not in patience. Secondly, Internet congestion makes learning resources miss or delay.According to this problem, this paper analyzes the methods to improve Internet更多还原