【作者】 谢晟；

【导师】 吴中福；

【作者基本信息】 重庆大学 ， 计算机系统结构， 2005， 硕士

【摘要】 随着互联网业务的进一步发展以及移动电话、PDA 和笔记本电脑等数字移动通信终端数量的增加,无线接入将逐渐成为互联网的主要接入方式,而一旦用户摆脱了网线的束缚,就希望能在任何地点、以任意的接入方式(有线或无线)、用固定的帐号和网络配置参数连接到Internet 或其所属网络,并且在移动的过程中不中断正在进行的网络应用,始终保持联机状态。移动IP 正是针对这种需求而产生的。移动IP 的设计目标就是让节点能够使用固定的IP 地址在不同的网段上切换,同时对上层应用保持透明,与底层物理链路无关。移动IPv6作为一项前沿的网络技术,具有广阔的应用前景和巨大的商业价值。但在推广到实际应用之前,移动IPv6 还需要多方面的改进,其中性能优化是当前众多学者研究的热点。而仅仅从协议本身来研究其性能是远远不够的,实验是最直观和最有说服力的方法。在本课题中,我们运用网络离散事件模拟软件NS-2搭建了较为复杂的基于WLAN 的移动IPv6 实验环境,分别从单个节点和整个网络的视角来观察瞬时带宽、切换延时、分组丢失、端到端延时、信道吞吐量和信令负载等网络性能参数,分析其变化规律和原因,并提出了一种路由优化策略。通过实验分析,我们观察到节点切换后的“双倍带宽”现象并分析了其成因、推出切换延时和分组丢失的计算公式、并得到以下几个结论:1)分组丢失不仅与切换延时有关,还与切换类型有关(从家乡链路切换到外地链路或从外地链路切换到外地链路);2)路由优化可能会增加切换延时和分组丢失;3)上层数据流会影响移动节点的切换行为;4)移动IPv6 的信令负载一般不会占用过多的网络带宽。更多还原

【Abstract】 Wireless Access will gradually become the primary Internet access method alongwith the further development of Internet services and the increase of the usage ofmobile phones, PDAs and laptops. Once the subscribers have broken away from thewire, they hope to use fixed accounts and networking configurations to connect to theInternet anywhere through arbitrary access modes (wired or wireless). And it is alsoexpected that network applications will not be interrupted during the node’s movementand always keep online. Mobile IP was born to meet this need and its goal is to enablethe node to switch between different subnets while keeping a fixed IP address andmaintaining transparent to up-layer applications as well as down-layer physical links.As a network technology on the cutting edge, Mobile IPv6 has an extensiveapplication prospect and enormous commercial value. However, before pushed intopractical application, it has several aspects to be improved among which theperformance optimization is the current researching hotspot. It is far from enough tostudy the performance from the protocol itself and the most intuitionistic andconvincing way is experiment. In this research, we used NS-2, a discrete eventsimulator for network research, to set up a fairly complicated WLAN-based MobileIPv6 experiment environment. We observed network performance parameters such asinstantaneous bandwidth, handoff latency, packet loss, end-to-end delay, channelthroughput and signaling load from the viewpoints of a single node and the wholenetwork respectively. The rules and related reasons of their variety were also analyzedand a policy of route optimization was advanced. Through the experiments and analyses,we discovered the “double bandwidth”phenomenon after a node’s handoff and got theformulas of handoff latency and packet loss and made the following conclusions: 1)Packet loss has relation with not only the handoff latency, but also the handoff type(from home link to foreign link or from foreign link to foreign link). 2) Routeoptimization may lead to a higher handoff latency and packet loss. 3) The up-layertraffic may have impact on the handoff behavior of the mobile node. 4) The signalingload of Mobile IPv6 will not impropriate too much network bandwidth generally.更多还原