this paper proposed a new end-to-end TCP performance improving mechanism, by using the interval movement cumulated of the packets received time on receiver, which can estimate the wireless link condition. Then it marks the ELN（Explicit loss notification）bit to notify the sender and TCP could be modified so as to refrain from going into congestion avoidance. Comparing the TCP Reno and the modified TCP ,by simulations using NS2，the results show it achieves an great improvement over mobile wireless networks and can work together with current security mechanism.Keywords：TCP ; Virtual NetWork Card; Wired-cum-Wireless Networks ; Performance Evaluation; Congestion Control end-to-end ; IPSec; VPN Architecture
目 录
学校代码10487 密级 I
摘 要 I
ABSTRACT II
目 录 IV
1 绪 论 1
1.1 研究背景 1
1.2 国内外研究现状 3
1.3 主要研究内容 6
2 无线网络VPN解决方案 8
2.1 无线网络TCP与VPN协议 8
2.2 无线TCP性能改进模型 15
2.3 TCP改进方案性能分析与IPSEC兼容性解决方案 22
2.4 本章小结 24
3 基于虚拟网卡的VPN体系结构 25
3.1 基于WINDOWS VPN系统设计 25
3.2 新的VPN体系结构图 28
3.3 虚拟网卡启动流程 32
3.4 报文处理过程的分析 33
3.5 本章小结 34
4 新的无线TCP性能改进方案 36
4.1 NS2仿真工具的介绍 36
4.2 MODIFIED-TCP的定义 37
4.3 MODIFIED-TCP的设计思想 38
4.4 时间变化累计的计算 42
4.5 MODIFIED-TCP改进的实现 43
4.6 本章小结 45
5 VPN系统结构分析和性能评价 47
5.1 与传统VPN体系结构的比较 47
5.2 TCP改进模型性能的评估标准 47
5.3 MODIFIED-TCP参数分析 48
5.4 MODIFIED-TCP性能分析 49
5.5 本章小结 52
6 总结与展望 54
6.1 总结 54
6.2 展望 55
致 谢 56
附录1 攻读学位期间发表论文目录 60
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