DTN网络数据传输性能优化研究

发布时间：2018-01-11 16:00

本文关键词：DTN网络数据传输性能优化研究　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：空间延迟容忍网络(Delay Tolerant Network,DTN)与地面有线网络存在着巨大差异:地面有线网络链路传输时延小,误码率低,TCP/IP协议中的传统拥塞控制算法能够得到良好地应用;而空间DTN链路环境中,传输时延大,误码率高,若继续使用TCP/IP协议中的传统拥塞控制策略,数据的传输效率将大大降低。针对上述问题,本文首先总结了国内外对提高空间网络数据传输性能所做出的各项工作。接着详细描述了传统TCP协议拥塞控制算法的几个阶段,指出了长时延对慢启动阶段的影响;高误码对丢包与拥塞判断的影响。并通过NS2仿真进一步证实了其结论的正确性。然后为了降低长时延对数据传输速率的影响,基于Vegas算法进行了两方面的改进:一是通过扩大初始窗口,使单位时间内获得更多ACK,加速慢启动阶段拥塞窗口的增长,从而获得更大吞吐量;二是考虑到Vegas算法可能过早结束慢启动阶段,使得在拥塞避免阶段逗留时间过长,大大降低了网络带宽利用率。因此本文采用加速增长拥塞避免阶段拥塞窗口值的策略,使其更快速的接近最佳窗口,从而提高链路吞吐量。通过NS2的对比仿真实验,可以看出,在短时间内,改进后的Vegas算法吞吐量要明显高于传统Vegas算法。为了更加准确的判断丢包是拥塞造成还是误码造成,本文采用了显式拥塞通知(ECN)机制来解决高误码所造成的影响。通过空间链路中间的路由器节点,能够更加准确,更加快速的通知发送端拥塞是否发生。在准确判断丢包的原因前提下,进一步划分拥塞状态,能够最大限度的利用带宽。最后,通过NS2的仿真实验,可以看出,在TCP连接当中,改进后的算法要优于Vegas算法。最后,基于CCSDS AOS标准和TCP分段(TCP-Splitting)技术搭建了空间网络数据传输的一个系统。通过TCP分段技术,使得空间内部网络能够使用传统TCP协议拥塞控制算法,而空间链路间则使用改进的Vegas算法。这样,减少了不必要损耗,并且能更快速地传输文件。在系统中传输文件,尤其是小文件,我们可以看出,改进后的算法要优于传统Vegas算法。
[Abstract]:Space delay tolerant network (Delay Tolerant Network, DTN) there is a huge difference with the ground cable network: ground cable network link small transmission delay, low error rate, the algorithm can get good application of TCP/IP protocol in the traditional congestion control; and the space DTN chain road environment, large transmission delay, high bit error rate, if continue to use the traditional congestion control strategy in TCP/IP protocol, data transmission efficiency will be greatly reduced. In order to solve the above problems, this paper first summarizes the work at home and abroad to improve the spatial network data transmission performance made. Then a detailed description of the several stages of the traditional TCP congestion control algorithm, points out the influence of long time delay of slow start the influence of high error on stage; packet loss and congestion judgment. And through the simulation of NS2 further confirmed the correctness of the conclusion. Then in order to reduce the long delay data transmission rate The effect, based on Vegas algorithm is improved in two aspects: one is by expanding the initial window, to obtain more ACK per unit time, accelerate the slow start phase of the congestion window growth, thereby gaining greater throughput; two is to consider the Vegas algorithm may end prematurely slow start phase, the sojourn time in congestion avoidance phase too long, greatly reduces the bandwidth utilization of the network. So this paper uses the accelerated growth of the congestion avoidance phase congestion window value strategy, make it more quickly approaching the optimal window, so as to improve the link throughput by NS2. The simulation experiment, we can see that in a short period of time, the Vegas algorithm improved the throughput are significantly higher than the traditional Vegas algorithm. In order to determine the packet loss is caused by congestion or more accurate error caused, the explicit congestion notification (ECN) mechanism to solve the impact caused by the high error. The router nodes space link intermediate, which is more accurate, notify the sender's congestion more quickly. In the premise of whether the accurate judgment of the causes of packet loss, further dividing congestion state, can maximize the use of bandwidth. Finally, through simulation experiments, NS2 can be seen in the TCP connection, the improved algorithm to better than Vegas algorithm. Finally, the CCSDS AOS standard and TCP segment based on (TCP-Splitting) technology to build a system of spatial data transmission network. Through the TCP segment technology, the space inside the network can use the traditional TCP congestion control algorithm, and the space link between the use of the improved Vegas algorithm. In this way, to reduce unnecessary the loss, and can transfer more quickly. The file transfer files on the system, especially the small file, we can see that the improved algorithm is superior to the traditional Vegas algorithm.

【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN919.3

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