平滑的Web文档预送

SMOOTHING THE WEB DOCUMENT PRESENDING

ＷｏｒｌｄＷｉｄｅＷｅｂ作为全球范围的分布式信息系统，其使用日益广泛，大量交互式应用的出现使用户对响应时间有较高的要求．服务器文档预送和非服务器站点的缓冲机制配合使用，可以显著改进Ｗｅｂ服务的响应性能．但是，由于预送增加了网络传输的阵发性，增加了报文重传和丢失，加大了网络排队延迟和平均队列长度，带来网络性能的下降．为了保持预送对用户服务质量（ＱｏＳ）的积极作用，同时减少对网络的负面影响，我们提出平滑的Ｗｅｂ预送策略，将预送文档的传输平展到实际的请求发出之前这一相当长的时间段内．通过简单的服务器发送速率控制，在预送的准确度较高时，网络性能的改进不但明显好于单纯的预送，与无预送的网络状态相比，也有较大的改进．

As a global distributed information system, World Wide Web (WWW) has seen a wide range of applications. Recently, various interactive applications challenge WWW with hard time requirement. Although document presending from WWW servers along with caching at non server sites is an effective technique to reduce user response time, it has negative effect on network performance because of the increased burstiness, resulting in more packet retransmission and loss, larger queuing delay and queue length. In order to meet the requirements of both user responsiveness and network performance, we propose a strategy of smoothing presending, i.e., expanding the transmission of documents to be present across the relative long time for user reading the document just downloaded. This method of rate control is applied to TCP , and shown effective through simulations, with improved network performance better than raw presending and even than no presending.