摘要
网上业务日益繁重，通信量的迅猛增长使得目前的网络数据传输方式需要改进，组播被认为是一种有效的传输方式，但还有几个问题需要加以解决，比如可靠性和拥塞控制。目前已经有一些可靠组播和组播拥塞控制协议和算法，但在传统网络的限制下，这些算法存在一些缺陷。而主动网络作为一种中间节点可编程网络体系结构，为解决可靠性等组播问题提供了一个新途径。本文主要研究主动网络技术在组播中的应用。
(1)分析连续实时流媒体的传输模型和组播数据丢失特性，提出了一种基于主动节点连续实时流媒体的可靠组播算法，通过NS2仿真实验证明，该算法能够有效降低报文的丢失率，减少服务器的重传次数，完成连续实时流媒体的可靠传输。
(2)分析主动网络的拥塞控制机制，在组播分层编码技术的基础上，给出了一种基于主动节点的组播拥塞控制算法，利用NS2进行了仿真，实验结果表明，该算法有比较好的TCP友好性和可扩展性，可以满足多媒体组播在网络异构条件下的拥塞处理。
最后展望了主动网络在组播应用中的前景和热点。
The transmission style of network data need to be improved on the condition that the operation of network is increasingly heavy and the communication quantum grows fast. Multicast is considered to be an efficiency transmission style, But it has several important matter to solve, including the reliability and congestion control. Although there are already many protocols and arithmetic of reliable multicast and multicast congestion control, these arithmetic has some bugs under the restrict of traditional network. The active network as a sort of new middle node is a system configuration of programming network, and offers a new approach of solving the multicast problems.
The paper analyses and researches the application in multicast through active network technique.
The paper analyses the transmission model of sequent real time flow of media and the losing characteristic of data, then puts forward the credibility multicast on the base of sequent real time flow of media of the initiative node. The experiment on NS2 proves that this method can efficiently reduce the losing rate and the resending times of server, and completes the transmission of sequent real time flow of media.
The paper analyses the mechanism of congestion control in initiative network, and on the base of bed coding technique of multicast, the bed multicast of initiative node is designed and imitated using NS2.The result of experiment indicates that this strategy strengthens the congestion detection of node, has much better TCP neighboring and extending, and accomplishes the congestion control of multicast well. Finally, the paper makes the prospect and hotspot of initiative network in the application of multicast.
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