【摘要】：隨著經(jīng)濟(jì)的不斷發(fā)展，網(wǎng)絡(luò)上的負(fù)載也越來(lái)越重，越來(lái)越多的網(wǎng)絡(luò)擁塞現(xiàn)象開(kāi)始顯現(xiàn)。所以，對(duì)于擁塞現(xiàn)象控制的研究也越來(lái)越重要。擁塞控制的機(jī)制根據(jù)其實(shí)現(xiàn)位置，可分為兩大類(lèi)：基于源端的算法（Source Algorithm）和基于鏈路的算法（Link Algorithm）。基于源端的算法主要以TCP協(xié)議內(nèi)容中擁塞控制機(jī)制的部分為主。雖然TCP協(xié)議中的擁塞控制機(jī)制在網(wǎng)絡(luò)中已成功運(yùn)行了很多年,但是僅僅依靠TCP協(xié)議提供的擁塞控制機(jī)制是無(wú)法滿足不斷增長(zhǎng)的網(wǎng)絡(luò)數(shù)據(jù)需求的。這就要求我們要將眼光放到網(wǎng)絡(luò)中間節(jié)點(diǎn)上去�，F(xiàn)今，基于鏈路算法的擁塞控制機(jī)制主要集中于中間節(jié)點(diǎn)的緩存隊(duì)列管理機(jī)制上，主要分為被動(dòng)隊(duì)列管理機(jī)制(PQM，Passive Queue Management)與主動(dòng)隊(duì)列管理機(jī)制(AQM, Active Queue Management)。由于被動(dòng)隊(duì)列管理存在“死鎖”、“全局同步”等問(wèn)題，而且主動(dòng)隊(duì)列管理可以預(yù)見(jiàn)地而非反應(yīng)式地丟棄分組，因而主動(dòng)隊(duì)列管理機(jī)制得到了更多研究者的關(guān)注。其中早期隨機(jī)檢測(cè)(Random Early Drop, RED)算法是主動(dòng)隊(duì)列機(jī)制中典型的應(yīng)用算法。 本文對(duì)主動(dòng)隊(duì)列管理算法進(jìn)行了詳細(xì)研究，其中包括RED、ARED、GRED、FRED等算法。針對(duì)RED算法中參數(shù)敏感性的問(wèn)題，，對(duì)RED算法進(jìn)行了改進(jìn)。并且利用網(wǎng)絡(luò)仿真工具在模擬的網(wǎng)絡(luò)擁塞環(huán)境下對(duì)算法性能進(jìn)行分析。本文設(shè)計(jì)了三種基于RED的改進(jìn)算法，RED-S，RED-T及RED-P。其中RED-P算法利用二次函數(shù)特性來(lái)增加丟包概率變化的平滑性，減小了平均隊(duì)列長(zhǎng)度的變化率，并且在不同區(qū)間采用了不同公式計(jì)算丟包概率，增加擁塞控制力度的同時(shí)保證了吞吐量，讓平均隊(duì)列長(zhǎng)度可以平滑的過(guò)渡，性能也最優(yōu)。本文選用了NS2這一網(wǎng)絡(luò)仿真工具，對(duì)改進(jìn)前后算法的運(yùn)行進(jìn)行了仿真，對(duì)擁塞場(chǎng)景進(jìn)行了設(shè)置，并且對(duì)改進(jìn)協(xié)議前后端到端的平均延時(shí)，平均隊(duì)列的長(zhǎng)度以及吞吐量等參數(shù)進(jìn)行了比較。 仿真表明：本文提出的RED-T，RED-S，RED-P算法能有效的改進(jìn)RED的參數(shù)敏感性的問(wèn)題，適度簡(jiǎn)化了參數(shù)設(shè)置。并且，在減小瓶頸段端到端延時(shí)的同時(shí)減小了平均隊(duì)列的波動(dòng)范圍與抖動(dòng)幅度，能維持幾乎接近的吞吐量。在保證改進(jìn)算法服務(wù)質(zhì)量的前提下，可以更好的應(yīng)付網(wǎng)絡(luò)的擁塞。
[Abstract]:With the development of economy, the load on the network becomes more and more heavy, and more network congestion appears. Therefore, the study of congestion control is becoming more and more important. Congestion control mechanisms can be divided into two categories according to their location: source-based algorithm (Source Algorithm) and link-based algorithm (Link Algorithm). The source-based algorithm is mainly based on the congestion control mechanism in the content of TCP protocol. Although the congestion control mechanism in the TCP protocol has been running successfully in the network for many years, the congestion control mechanism provided by the TCP protocol alone can not meet the increasing demand for network data. This requires us to look at the network in the middle of the node to go. Nowadays, the congestion control mechanism based on link algorithm is mainly focused on the buffer queue management mechanism of intermediate nodes, which is divided into passive queue management mechanism (PQMN passive Queue Management) and active queue management mechanism (AQM, Active Queue Management). Because of the problems of "deadlock" and "global synchronization" in passive queue management, and active queue management can discard packets predictably rather than reactive, active queue management mechanism has attracted more attention. Among them, early random detection (Random Early Drop, RED) algorithm is a typical application algorithm in active queue mechanism. In this paper, active queue management algorithms are studied in detail, including red / red algorithm. Aiming at the problem of parameter sensitivity in RED algorithm, the RED algorithm is improved. Network simulation tools are used to analyze the performance of the algorithm in the simulated network congestion environment. Three improved algorithms based on RED are designed in this paper. The RED-P algorithm makes use of quadratic function to increase the smoothness of packet loss probability, reduces the change rate of average queue length, and uses different formulas to calculate packet loss probability in different regions. Increase congestion control while ensuring throughput, so that the average queue length can smooth the transition, and the performance is optimal. In this paper, the network simulation tool NS2 is used to simulate the algorithm before and after the improvement, and the congestion scenario is set up, and the average end-to-end delay before and after the improved protocol is given. The average queue length and throughput are compared. Simulation results show that the proposed RED-TX RED-S RED-P algorithm can effectively improve the parameter sensitivity of RED and simplify the parameter setting appropriately. In addition, the end-to-end delay of the bottleneck segment is reduced while the fluctuation range and the jitter amplitude of the average queue are reduced, which can maintain an almost close throughput. Under the premise of improving the QoS of the algorithm, it can better deal with the congestion of the network.
【學(xué)位授予單位】：內(nèi)蒙古科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TP393.06

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