發(fā)布時(shí)間：2018-01-11 16:00

  本文關(guān)鍵詞：DTN網(wǎng)絡(luò)數(shù)據(jù)傳輸性能優(yōu)化研究　出處：《電子科技大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 空間DTN網(wǎng)絡(luò) Vegas算法 顯式擁塞通知 TCP分段連接

【摘要】：空間延遲容忍網(wǎng)絡(luò)(Delay Tolerant Network,DTN)與地面有線網(wǎng)絡(luò)存在著巨大差異:地面有線網(wǎng)絡(luò)鏈路傳輸時(shí)延小,誤碼率低,TCP/IP協(xié)議中的傳統(tǒng)擁塞控制算法能夠得到良好地應(yīng)用;而空間DTN鏈路環(huán)境中,傳輸時(shí)延大,誤碼率高,若繼續(xù)使用TCP/IP協(xié)議中的傳統(tǒng)擁塞控制策略,數(shù)據(jù)的傳輸效率將大大降低。針對(duì)上述問題,本文首先總結(jié)了國內(nèi)外對(duì)提高空間網(wǎng)絡(luò)數(shù)據(jù)傳輸性能所做出的各項(xiàng)工作。接著詳細(xì)描述了傳統(tǒng)TCP協(xié)議擁塞控制算法的幾個(gè)階段,指出了長時(shí)延對(duì)慢啟動(dòng)階段的影響;高誤碼對(duì)丟包與擁塞判斷的影響。并通過NS2仿真進(jìn)一步證實(shí)了其結(jié)論的正確性。然后為了降低長時(shí)延對(duì)數(shù)據(jù)傳輸速率的影響,基于Vegas算法進(jìn)行了兩方面的改進(jìn):一是通過擴(kuò)大初始窗口,使單位時(shí)間內(nèi)獲得更多ACK,加速慢啟動(dòng)階段擁塞窗口的增長,從而獲得更大吞吐量;二是考慮到Vegas算法可能過早結(jié)束慢啟動(dòng)階段,使得在擁塞避免階段逗留時(shí)間過長,大大降低了網(wǎng)絡(luò)帶寬利用率。因此本文采用加速增長擁塞避免階段擁塞窗口值的策略,使其更快速的接近最佳窗口,從而提高鏈路吞吐量。通過NS2的對(duì)比仿真實(shí)驗(yàn),可以看出,在短時(shí)間內(nèi),改進(jìn)后的Vegas算法吞吐量要明顯高于傳統(tǒng)Vegas算法。為了更加準(zhǔn)確的判斷丟包是擁塞造成還是誤碼造成,本文采用了顯式擁塞通知(ECN)機(jī)制來解決高誤碼所造成的影響。通過空間鏈路中間的路由器節(jié)點(diǎn),能夠更加準(zhǔn)確,更加快速的通知發(fā)送端擁塞是否發(fā)生。在準(zhǔn)確判斷丟包的原因前提下,進(jìn)一步劃分擁塞狀態(tài),能夠最大限度的利用帶寬。最后,通過NS2的仿真實(shí)驗(yàn),可以看出,在TCP連接當(dāng)中,改進(jìn)后的算法要優(yōu)于Vegas算法。最后,基于CCSDS AOS標(biāo)準(zhǔn)和TCP分段(TCP-Splitting)技術(shù)搭建了空間網(wǎng)絡(luò)數(shù)據(jù)傳輸?shù)囊粋�(gè)系統(tǒng)。通過TCP分段技術(shù),使得空間內(nèi)部網(wǎng)絡(luò)能夠使用傳統(tǒng)TCP協(xié)議擁塞控制算法,而空間鏈路間則使用改進(jìn)的Vegas算法。這樣,減少了不必要損耗,并且能更快速地傳輸文件。在系統(tǒng)中傳輸文件,尤其是小文件,我們可以看出,改進(jìn)后的算法要優(yōu)于傳統(tǒng)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.

【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN919.3

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相關(guān)期刊論文 前1條

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本文編號(hào)：1410196