【作者】 贾楠；

【导师】 张大坤；

【作者基本信息】 沈阳工业大学 ， 计算机技术， 2005， 硕士

【摘要】 为了提供东北地区民航网络通信的优质服务,保证通信畅通,转报不失为一条很好的途径。由于每天有成千上万份报文进入转报机,极易造成网络拥塞,形成堵报、漏报等问题,从而造成安全事故。要解决这些问题就必须要优化现有网络,试图从理论上改变网络结构,使之尽量减少报文拥塞,避免事故发生。目前只有在计算机网络服务质量的领域才能解决这些问题。拥塞控制中的区分服务公平性问题则是转报部分的重点研究范围。 IP网络中主要采用综合服务(IntServ)、区分服务(DiffServ)和多协议标记交换(MPLS)来实现QoS,其中区分服务作为一种可扩展性较好的QoS体系结构在网络设计中逐渐得到广泛认可。拥塞是网络服务质量中需要解决的一个主要问题。随着多媒体业务的广泛应用,使得互联网已经不可能只依靠基于源端的TCP拥塞控制,路由器本身也应主动参与到拥塞控制中来,所以基于中间节点的拥塞控制机制逐渐地成为目前研究的重点。队列管理是拥塞控制中重要的组成部分。在资源共享环境中,一定会有各共享者之间的公平性问题,具体到DiffServ,指同一聚集流内各微流共享资源。分布式主动队列管理算法结构和区分服务类似并且能够保证流与流之间的公平带宽分配。可以把分布式主动队列管理算法和区分服务模型相结合,以解决DiffServ网络中的公平性问题。 本文重点讨论区分服务模型的公平性问题。首先,介绍了网络拥塞的基本概念和产生拥塞的基本原因以及为解决拥塞问题可以采用的基于源端的控制机制和基于路由器的控制机制;其次,重点介绍了目前较为流行的四种能保证公平性的主动队列管理算法;第三,本文详细讨论了区分服务的体系结构和特点;最后,为了能在DiffServ模型下实现公平性,把一种分布式主动队列管理算法(SCALE-WFS)结合到DiffServ模型中。通过对网络模型的仿真和结果分析,显示了该模型能够改善DiffServ网络的公平性。更多还原

【Abstract】 Message Switch is one of the best ways to guarantee the message fluency in order to offer high quality service in the air communication of the North Air Management Bureau (NTAMB). The congestion of network, however, is likely to occur when thousands of messages come into the Unit Message-Switching system. The safety problem caused by message jam and message underreport has been concerned by researchers in this field. Optimization of the existed network is used to solve the problem in the thesis, which can avoid the problem by changing the structure of the network on theory to reduce the message jam. At present, the congestion of network only can be solved in the field of Quality of Service (QoS) of computer network. In the field of Message Switch, the research is focused on the Fairness problem of the differentiated services in congestion control.Integrated services (IntServ), differentiated services (DiffServ) and Multiprotocol Label Switching (MPLS) are adopted to improve the QoS of IP networks. Differentiated Services is widely recognized since its scalability. Network congestion is an important issue of network QoS. With the development of multimedia application, Fairness among different flows emerges. Consequently, network congestion can not be solved only depending on TCP congestion control which is implemented in source node. Router should actively play an important role in congestion control, so congestion control based on the middle node gradually becomes the main direction in current research. For DiffServ, the fairness means that every micro-flow in the same aggregated flow can fairly share the resources. Queue management is a component in the congestion control mechanism. The distributed active queue management has a similar architecture toDiffServ and can assure fair bandwidth allocation among flows. Integrating distributed active queue management with DiffServ model to solve the fairness problem is proposed.Fairness problem in the DiffServ model is mainly discussed in this paper. Firstly the concept of network congestion and the causes of the problem are introduced;then the congestion control mechanisms based on source node and on middle nodes are briefly described as the solution of the problem. Four active queue management algorithms are presented and the structure of DiffServ and its characteristics are discussed in detail. Finally, a modified model merging SCALE-WFS algorithm with DiffServ model is proposed to achieve fairness in DiffServ model. Simulated results and the analysis show that this model can improve the fairness in DiffServ networks.更多还原