【作者】 王玉；

【导师】 舒勤；

【作者基本信息】 四川大学 ， 信号与信息处理， 2006， 硕士

【摘要】 计算机网络在过去的十几年中经历了爆炸式的增长，随之而来的是越来越严重的拥塞问题。自从Jacobson于1988年提出网络拥塞控制的概念以来，拥塞控制理论和算法引起了极大的关注。本文着重对参数自适应的TCP友好拥塞控制算法进行研究，即如何在拥塞控制的目标下尽可能的保证网络资源占用的公平性。 TCP是Internet上最主要的传输协议，尽管TCP非常适合于诸如批量数据传输应用，但并不适合于多媒体实时应用。因此目前网络中，大量的多媒体应用利用UDP传输协议来传送资料。但由于UDP没有提供拥塞控制机制，多媒体应用很难得到平稳的传输速率来维持使用者的舒适度。为了在长时间的竞争环境下能与TCP资料流获得相同的带宽占有率且得到较平稳的传输速率，所以才发展出TCP友好性控制协议。 TCP友好(TCP-friendly)的定义为“非TCP流在长期范围内吞吐量近似等于相同情况下的TCP流的吞吐量”。GAIMD(General Additive Increase and Multiplicative Decrease)算法是目前比较常见的TCP友好性拥塞控制算法，已经在互联网的TCP拥塞控制算法中得到了应用。其主要原理是接收方反馈一个二进制位的欠载或过载信息，接收方根据此二进制信息，增加发送窗口一个α大小或将发送窗口缩减为原来的β倍的算法来调节发送方的负载。然而GAIMD算法并未达到良好的TCP友好性。本文中提出动态加权GAIMD和动态内插GAIMD两种方法来计算所需要的α值。动态加权GAIMD和动态内插GAIMD，根据每个往返时间内计算出的封包遗失率来得到符合当前网络环境的最佳α值，以求达到最佳的TCP友好性。本文方法能对网络流量突发变化做出及时反应。仿真结果表明本法具有和GAIMD相当的网络拥塞控制性能，但比更多还原

【Abstract】 The computer network has had an explosive development in the past years, but at the same time, it bring a sever problem: congestion. Congestion control has arisen great attention since Jacobson brought forward the concept of congestion control in 1988. In this paper an adaptive TCP-friendly congestion control algorithm has been investigated, which is mainly about how to achieve fair bandwith of the network under the objective of congestion control.TCP is the major protocol of the Internet. Although TCP protocol is fit for the batch data transmission application very much, it’s not fit for the real-time multimedia application. So in the current network, many applications of streaming multimedia use the UDP protocol. But the UDP protocol cannot smooth the sending rate to maintain the user-perceived quality, because it doesn’t provide congestion control mechanism. Therefore, the TCP-friendly protocol has been developed to suit to these applications. A TCP-friendly protocol flow has the similar sending rate with a TCP flow under the same condition.The algorithm of GAIMD, namely general additive increase and multiplicative decrease, which is thought a common TCP-friendly algorithm for congestion avoidance, has been applied widely in TCP congestion control. Its principium is that the receiver feedback a binary bit that indicates the information of underload or overload to the sender, and the sender adjusts the load with GAIMD algorithm更多还原