现代社会对信息的需求越来越大,Internet对于信息的传播与获取变得越来越重要,近年来微电子技术、计算机技术、多媒体技术的迅猛发展,使得Internet上由原来的只提供Best-effort的简单数据文件传送的服务,发展到普遍提供实时视频、音频通信及动画、广告等其他娱乐服务,带动了网 In the modern society, the demand for information is getting bigger and bigger. The Internet becomes more and more important for the dissemination and acquisition of information. In recent years, the rapid development of microelectronic technology, computer technology and multimedia technology makes the Internet from the original offering Best- effort to provide simple data file delivery services to the general provision of real-time video, audio communications and animation, advertising and other entertainment services, driven by the network