【作者】 范定国；

【导师】 段富；

【作者基本信息】 太原理工大学 ， 计算机软件与理论， 2004， 硕士

【摘要】 网络缓存(Web Caching)把经常访问的网络对象在访问开销较少的网络节点上存一个副本，当用户再次访问这些对象时，可以直接从这个开销较少的网络节点上得到满足。从而在有限的带宽内，达到缩短用户等待时间、提高网络性能和网络可扩展性的目的，对于提高Internet访问效率具有重要意义。 网络缓存分单机缓存代理服务器缓存和协作缓存(Cooperative Caching)，三个层次。其中协作缓存是当前研究的热点。论文在对网络缓存技术的原理、现状和发展趋势综述的基础上，对RCD(Reduced Cache Digests)表达的网络缓存协作进行了研究，提出了精简的缓存摘要(RCD)网络缓存内容的表达方法。该方法在缓存摘要(CD)的基础上，将网络对象进一步分为最近访问的、最频繁访问的和很少访问的三类，那么其中最近访问的和最频繁访问的两类Web请求在将来最有可能再次发生。RCD只把前两类网络对象映射到缓存目录中，这样可减少缓存目录的存储空间，并且由于包含了网络对象的 太原理_仁大学硕士研究生学位论文访问频率，所以特别适合于为具有相同访问特性的用户群提供缓存服务。为此，论文讨论了在具有7层交换功能的交换机上，建立、更新和访问RCD缓存目录的算法。最后在对同一局域网上的不同用户组访问特性统计分析的基础上，对分布在本地交换机上的RCD缓存协作进行了讨论。 理论分析和模拟实验表明，基于RCD的网络缓存协作方案，克服了代理被所有的交换机共享和代理之间负载平衡的缺点，并且充分的发挥7层交换机的内容感知功能，为本地用户提供了一种快速有效的访问Internet的途径。更多还原

【Abstract】 Web caching is a technique applied in Internet, with which the frequently accessed web objects are copied in a more easily accessed network node. Web caching can shorten clients’ waiting time and improve Internet’s performance without bandwidth increase. So it plays an important role in improving the efficiency of accessing Internet.Web caching has three developing steps those are browser caching, proxy caching and cooperative caching. Among them, cooperative caching is the focus of current study. After recounting the theory, status quo and develop trend of web caching, this article puts out the RCD(Reduced Cache Digests) expression of the cached content and studies cooperative web caching using RCD expression. In RCD, the contents cached in proxy are classified into three groups: the recently accessed, the frequently accessed and the rarely accessed. Because the last group contributes nothing to the whole cache system, RCD only express the first two groups. Thus the dimension of the cached content’s index is shortened. On the other hand, RCD especially adapts to servicing for client clusters with the same favoritism to web content, because it can store the accessed frequency of web objects. Based on RCD’s frequency-storing characteristic, this article discusses the arithmetic of creating, renewing and accessing RCD index. Finally, considering the users’accessing-frequency, cooperative web caching using RCD index, which is distributed in local switches, is discussed.Academic study and simulative experiment show that the problem tnat each proxy shared by all clients and balancing loading between proxies can’t be achieved simultaneously is conquered by the cooperative caching plan based on RCD . In this plan, a L7 switch with RCD provides a fast and effective way for local user to access Internet, resulting from its content-awareness ability exerted fully by RCD.更多还原