TCP-Rab： a receiver advertisement based TCP protocol

With the evolution of network technologies, the deficiencies of TCP protocol are becoming more and more distinct. The new TCP implementation, called Receiver Advertisement Based TCP (TCP-Rab) proposed here to eliminate these deficiencies, adopts two basic mechanisms: (1) Bandwidth Estimation and (2) Immediate Recovery. Bandwidth estimation is carried out at the receiver, and the result is sent back to the sender via the acknowledgments. Immediate Recovery guarantees high performance even in lossy link. Rab can distinguish the reason for packet loss, and thus adopt appropriate recovery strategy. For loss by network congestion, it will back off its congestion window, and for loss by link errors, it will recover the congestion window immediately. Simulations indicated that Rab has superiority over other TCP implementations.

TCP-Rab的吞吐量模型及实验研究

基于接收端通告的TCP(TCP-Rab,receiver advertisement based TCP)协议是我们实现的一种新的TCP协议,在文献[1]中对TCP-Rab的算法设计、实现进行了详细阐述。本文对TCP-Rab进行了少量改进,重点导出了TCP-Rab的吞吐量性能模型,并对TCP-Rab进行了试验研究。该模型采用统计的方法,在导出TCP-Rab的吞吐量性能模型的时候,不仅考虑了TCP连接的拥塞避免阶段对吞吐量的影响,也考虑了慢启动阶段对吞吐量的影响,同时还考虑了一个发送窗口内多个数据包随机丢失对吞吐量的影响,因此该模型能适用于实际的网络环境中。

一种基于带宽估计的战术互联网TCP改进机制

无线的战术互联网通常面临复杂的电磁环境,高误码率、终端的频繁移动等恶劣的通信环境使得针对有线网络设计的TCP协议传输性能急剧下降。针对战术互联网提出了一种基于带宽估计的TCP改进机制,该机制利用TCP确认帧携带的数据包到达时间来估算带宽,并用动态的低通滤波器来平滑带宽的估计值。在此基础上用带宽的估计值更新拥塞窗口,避免在发生链路错误时启动拥塞控制机制,由此提高TCP在战术互联网中的性能。实验结果表明,该算法能减少链路差错对TCP性能带来的影响,提高TCP在战术互联网上的传输性能。

卫星互联网TCP拥塞控制算法

为解决TCP Vegas拥塞控制算法无法适应卫星互联网场景的问题,分析该问题导致吞吐量性能降低的原因,提出一种基于链路长度计算结合带宽估计判决的Vegas-W算法。通过计算通信链路长度修正往返时延,结合带宽估计判决增加带宽竞争力,使Vegas拥塞控制算法在时延突变的情况仍保持较高吞吐量,适应卫星互联网星座动态环境特点。NS2仿真结果表明,Vegas-W算法相比Vegas算法在卫星互联网场景中吞吐量性能提高了40%,有效降低时延突变和带宽竞争不足给Vegas算法造成的不利影响。

一种基于带宽估计的无线网拥塞控制机制

针对无线网提出了一种基于带宽估计的拥塞控制机制。该机制利用TCP确认帧携带的数据包到达时间来估算包到达速率,从而得到带宽的估计值。在此基础上用带宽的估计值更新拥塞窗口,避免在发生链路错误时启动拥塞控制机制,由此提高了TCP在无线网上的性能 。实验结果表明,算法能减少链路差错对TCP性能带来的影响,提高了TCP在无线网上的吞吐率。

改进的无线网络自适应传输控制协议

传输控制协议(TCP)用于无线数据传输时性能较差,且网络资源利用率低。为此,提出一种自适应无线环境的TCP改进算法。在数据发送端采用带宽估计算法优化慢启动阈值和拥塞窗口尺寸,与具有显式拥塞通知的路由器配合区分分组丢失性质,同时实时监测误码丢包率,并根据监测结果自适应调整TCP段尺寸。仿真结果表明,改进的TCP的吞吐量在误码率为1E–4时高于TCP-Jersey近30%,高于TCP_SACK近59%。

On Approaches to Congestion Control over Wireless Networks

Congestion control in wireless networks has been extensively investigated over the years and several schemes and techniques have been developed, all with the aim of improving performance in wireless net-work. With the rapid expansion and implementation of wireless technology it is essential that the congestion control problem be solved. This paper presents a survey of five congestion control schemes which are dif-ferent in slow start threshold calculation, bandwidth estimation, and congestion window manipulation. A comprehensive comparison of these approaches is given in relation to assumptions, bandwidth estimation, congestion window size manipulation, performance evaluation, fairness and friendliness and improved throughput.