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研究生:王鑫一
研究生(外文):Hsin-Yi Wang
論文名稱:植基於無線網路多重跳躍點之TCP Vegas效能改善
論文名稱(外文):Performance Improvement on TCP Vegas Based on Multi-hop Wireless Network
指導教授:朱延平朱延平引用關係
指導教授(外文):Yen-Ping Chu
口試委員:陳錦杏許玟斌黃一泓
口試委員(外文):Chen Chin-HsingHuang Yi-Hung
口試日期:2010-12-31
學位類別:碩士
校院名稱:東海大學
系所名稱:資訊工程學系
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2010
畢業學年度:99
語文別:中文
論文頁數:48
外文關鍵詞:TCP VegasCWNDDiffNS2
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本篇論文針對TCP Vegas在無線網路環境中,修改CWND(Congestion Window, CWND)使其快速增量達到穩定狀態。TCP Vegas是以量測RTT為調整CWND依據,並且以預設的α與β值比較後作為調整CWND的大小,因此出現調整CWND的速率不夠快而無法有效利用頻寬的問題。依據無線網路環境參數的推算,其實無線網路的整體緩衝區(buffer),不像有線網路那麼多,還有從TCP Vegas公式和本篇文章對無線網路環境的觀察,得知Diff的值就是在預估線上整個還未完成的封包數量,所以還未收到ACK的封包數量,就幾乎相等於CWND值,因此,本篇提出的建議方法,將TCP Vegas的CWND值的變化控制介於α到β+1之間。經由NS2(Network Simulator, version 2)模擬器實驗結果獲得驗證-在無線網路及受到背景干擾的情況下,我們的方法確實比TCP Vegas更快將CWND調整到穩定狀態並且獲得較高的吞吐量。
The main focus of this thesis is to utilize TCP Vegas by modifying the increment speed of congestion window (CWND) in wireless network environments. By doing so, TCP Vegas may rapidly increase its CWND and reaches the steady state sooner.
Traditionally, TCP Vegas adjust its CWND based on the measurement of RTTs (Round Trip Time). It uses the CWND default value of α and compares it against β, and then adjusts the size of the CWND accordingly. This CWND adjustment approach is slow and inefficient, which may result in bandwidth underutilization. In fact, from the observation of wireless network as well as the TCP formula in this thesis, wireless network buffers are most likely less then wired network according to the wireless network environments parameters settings, and the Diff value is used to estimate the total amount of packets has been transmitted but still waiting for conformation, Hence, the amount of packets that are still waiting for conformation are very close approximation of the CWND value. Therefore, this thesis proposed a method that controls the variation of TCP Vegas CWND between α and β +1.
From the results of NS2 simulations, we verified that the CWND adjustment of our proposed method not only adjust faster than traditional TCP Vegas, but also reaches the steady state sooner. The benefit of such changes gained higher throughput utilization ratio and also helps in decreasing the background interference issues.

中文摘要 i
Abstract ii
致謝 iii
圖目錄 vi
表目錄 vii
第一章 導論 1
1.1 簡介 1
1.2 研究動機 2
1.3 研究目的 2
1.4 論文架構 3
第二章 文獻探討 4
2.1 IEEE 802.11介紹 4
2.2 TCP介紹 16
2.3 TCP 壅塞控制 18
2.4 TCP New Reno機制 20
2.5 TCP Vegas機制 23
2.6 現有改進TCP壅塞控制機制 28
第三章 TCP Vegas改善的方法 31
3.1 TCP Vegas的觀察 31
3.2 建議的方法 31
第四章 模擬實驗與分析 33
4.1 模擬環境 33
4.2 實驗結果 35
第五章 結論與未來展望 38
參考文獻 39



[1]J. S. Ahn, P. Danzig, Z. Liu, and L. Yan, “Evaluation of TCP Vegas: emulation and experiment,” Computer Communication Review, vol. 25, no. 4, pp. 185-195, Oct. 1995.
[2]L. Brakmo and L. Peterson. “TPC Vegas: End to End Congestion Avoidance on a Global Internet,” IEE Journal on Selected Areas in Communication, vol. 13, no. 8, pp. 1465-1480, Oct. 1995.
[3]Lawrence S. Brakmo, Sean W. O’Malley, and Larry L. Peterson, 1994, “TCP Vegas: New Techniques for Congestion Detection and Avoidance,” in Proceedings of the ACM SIGCOMM’94 Symposium, London, U.K., pp.24-35.
[4]Y. C. Chan, C. L., C. T. Chan and C. Y. Ho, “Improving Performance of TCP Vegas for High Bandwidith-Delay Product Networks”, Proceedings of IEEE Advanced Communication Technology, vol. 1, pp.987-997.2006.
[5]S. Floyd, T. Henderson, A. Gurtov, "The NewReno Modification to TCP's Fast Recovery Algorithm", RFC3782, 2004.
[6]G. Holland and N. Vaidya, “Impact of routing and link layers on TCP performance in mobile ad hoc networks,” IEEE Wireless Communications and Networking , vol. 3, pp. 1323-1327,1999.
[7]IEEE std. 802.11, “Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specification, ”1999.
[8]V. Jacobson “Congestion Avoidance and Cotrol”, ACM SIGCOMM ‘88﹐pp.273-288, 1988.
[9]V. Jacobson “Modified TCP Congestion Avoidance Algorithm”, mailing list, end2end-interest, 30 Apr. 1990.
[10]T. Kelly, “Scalable TCP:Improving Performance in High Speed Wide Area Networks”, ACM SIGCOMM Computer Communication Review, vol. 33,pp.83-91,2003.
[11]M. Mathis, J. Mahdavi, S. Floyd, and A. Romanow, “TCP Selective Acknowledgement Options, ”IETF RFC 2018, 1996.
[12]J. Postel, “Transmission Conter Protocol,” Request for Comments, RFC 793, Protocol Specification, DARP Internet Program, Sep. 1981.
[13]W. Stevens, “TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery Algorithms,” IETF RFC 2001, 1997.
[14]Sarut Vanichpun and Wu-chun Feng, 2002, “On the Transient Behavior of TCP Vegas,” in Proceeding of the Eleventh IEEE International Conference on Computer Communications and Networks, Miami, Florida, USA, pp. 504-508.
[15]Network Simulator 2 (NS2) http://www.isi.edu/nsnam/ns

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