可避免数据包乱序的网络层软切换方法及其性能分析  

Performance Analysis of a Network-Layer Soft Vertical Handoff Scheme Without Packet Reordering

作　　者：舒童[1,2] 刘敏[1] 李忠诚[1] 

机构地区：[1]中国科学院计算技术研究所网络技术研究中心,北京100190 [2]中国科学院研究生院信息科学与工程学院,北京100190

出　　处：《计算机学报》2010年第1期23-35,共13页Chinese Journal of Computers

基　　金：国家自然科学基金(60803140;60970133);国家"九七三"重点基础研究发展规划项目基金(2007CB310702);北京科技新星项目资助~~

摘　　要：随着异构无线网络的融合和全IP网络的推广,网络层软切换方法不断演进,用以提高垂直切换的性能.但是,现有的软切换方法在下行垂直切换过程中会造成严重的数据包乱序.为此,文中在讨论下行垂直切换时数据包乱序的原因之后,提出了一种新型网络层软切换方法——SHORDER.该方法根据移动终端与其家乡代理之间的交互信令对终端所收数据包进行适当的缓存,能有效避免移动终端因下行垂直切换接收到乱序的数据包.该方法所具有的网络层独立性使其能与各种传输层协议及其改进协议相兼容.此外,文中还从理论上定量地分析了所提方法对TCP应用的切换时延、有效吞吐量及拥塞窗口的影响,并与现有的典型网络层软切换方法进行了比较.通过比较,得出了SHORDER机制的适用条件,并基于此,进一步改进了SHORDER方法.最后,在原型系统上的实验显示出了所提机制便于部署的优点以及该机制在其适用条件下的良好性能.此外,实验结果还显示出与数值分析结果的一致性.With the integration of heterogeneous wireless technologies and the popularization of all-IP networks,network-layer soft handoff approaches have gradually evolved to improve the performance of vertical handoffs（VHOs）.Unfortunately,the existing soft handoff approaches lead to plenty of out-of-order packets during downward VHOs.In this paper,the authors present a new network-layer soft vertical handoff scheme,called SHORDER.In the scheme,the mobile node（MN）starts or stops buffering packets from its new network based on a few interactive messages with its home agent （HA）. With the buffering technique, the scheme ean prevent mobile terminals from receiving reordered packets caused by downward VHOs, and is compatible with various transport-layer protocols and their variants due to its independence. Then, the authors theoretically analyze the influence of the proposed scheme on the handoff latency, the good- put and the congestion window of the TCP in comparison with a typical existing network-layer soft VHO method. Additionally, the authors also derive the applicable condition of the SHORDER scheme. Experiments show that the deployment of the proposed scheme is easy and the scheme has better performance under its applicable condition, further, experimental and analyticat results are consistent with each other. Finally, based on the applicable condition of the SHORDER scheme, the scheme further is improved.

关 键 词：下行软切换 数据包乱序 TCP吞吐量 快速重传 异构无线网络 

分 类 号：TP393[自动化与计算机技术—计算机应用技术]