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研究生: 蘇倍豪
研究生(外文): Bei-Hao Su
論文名稱: 可支援長距離網路上高速傳輸之動態TCP Vegas設計
論文名稱(外文): Design of A Dynamic TCP Vegas to Support Long-distance High Speed Networks
指導教授: 洪盟峰
指導教授(外文): Mong-Fong Horng
學位類別: 碩士
校院名稱: 樹德科技大學
系所名稱: 資訊工程學系
論文出版年: 2008
畢業學年度: 96
語文別: 中文
論文頁數: 65
中文關鍵詞: 壅塞控制高速傳輸長距離網路TCP Vegas服務品質保障
外文關鍵詞: congestion controlhigh-speed transmissionlong-distance networkTCP Vegasquality of services
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  • 被引用:0
  • 點閱:44
  • 評分:*****
  • 下載:3
  • 書目收藏:0
本文主要目的是以不同於目前標準TCP演算法(TCP New Reno)的TCP Vegas機制為基礎,利用量測來回傳輸時間Round-Trip Time(RTT)數值來計算連線實際吞吐量,並比較其與預計吞吐量之間差異值與α、β兩數值之間的差異,透過差異值與其預設上、下限的關係,來評估目前網路壅塞情況,以及動態調整TCP Vegas的視窗大小、另外之α、β值的方式,解決標準TCP Vegas在長距離高傳輸頻寬網路環境中,兩端點連線之間的頻寬吞吐量過小問題。本論文中,吾人捨棄傳統TCP所採用以封包遺失作為調節依據的作法,改採利用RTT量測值的變動差異與預設控制範圍(α、β)之關係來評估目前網路壅塞程度,並籍此作為傳送端cwnd提結的機制。其次,雖然此方式可較標準TCP的加法遞增乘式遞減(AIMD)機制來得有效率,但所設定控制範圍參數(α、β)如為固定值容易造成cwnd的管理過於保守,此一特性將使長距離連線無法有效的充分利用高速網路頻寬。因此本文提出可適用長距離網路的動態TCP Vegas設計方法,可以藉由動態調整的α、β值,可以不斷地因應目前網路通道的變化,改變cwnd管理方式來提高頻寬使用率。透過模擬實驗的驗證,顯示所提方式在不同傳輸距離、不同傳輸頻寬的狀況下,在點對點吞吐量上,針對瓶頸鏈路之頻寬分別為100Mbps、155Mbps及622Mbps時,量測到本機制可改善標準TCP Vegas吞吐量倍率分別為7.13、11.87及27.79倍,平均改善標準TCP Vegas倍率為15.597倍,由此可證實本機制可有效善目前標準TCP Vegas的效能。
The main purpose of this research is to propose a new scheme to improve the throughput of long-distance TCP connections. The proposed scheme is a variation of TCP Vegas. Differing from the current standard TCP algorithms (TCP New Reno), the proposed scheme uses Round-Trip Time (RTT) to derive the actual throughput of the target connection. According to the difference between the actual throughput and the desired throughput, the congestion window size is adjusted to either speed op or slow down the TCP connection. For efficient response, the strategy of window-adjustment is composed four parts to meet the requirements of four stages of a TCP connection. We improve the constant-interval approach of TCP Vegas. In the new scheme, dynamic adjustment of TCP Vegas α, β value is designated to enhance the throughput of the standard TCP Vegas. Simulation results show that in various conditions of bandwidth and distance, the proposed scheme effectively improves the throughput of standard TCP Vegas. Besides, the analysis of fairness among homogenous and heterogenous TCP connections is also presented.
摘要  i
ABSTRACT  ii
目錄  iii
圖目錄  iv
表目錄  vi
一、緒論  1
1.1 研究背景  1
1.2 研究動機  3
1.3 研究目的  4
1.4 文章組織  4
二、文獻探討  5
2.1 長距離高速傳輸網路特性分析  5
2.2 現有TCP壅塞控制機制之研究  8
2.2.1 TCP New Reno機制  8
2.2.2 TCP Vegas機制  10
2.3 現有改進TCP壅塞控制機制之研究  12
2.3.1依據封包遺失為調整壅塞視窗基礎之改進方式  13
2.3.2依據量測RTT為調整壅塞視窗基礎之改進方式  16
三、可支援長距離網路上高速傳輸之動態TCP Vegas設計  21
3.1目前TCP Vegas在長距離高速傳輸網路之效能問題  21
3.2可支援長距離網路上高速傳輸之動態TCP Vegas設計方法  23
四、模擬與分析  37
4.1實驗目標與環境  37
4.2實驗結果與分析  38
五、結論與未來展望  63
參考文獻  64
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[18]NS2, Network Simulator version 2, http://www.isi.edu/nsnam/
[19]Jain’s Fairness Index, http://www.cs.berkeley.edu/~kfall/EE122/lec21/sld005.htm
                                                                                                                                                                                                                                                                                                                                                                                                               
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