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研究生:林俊賢
研究生(外文):Chun-Hsien Lin
論文名稱:在AdHoc無線網路上具有ACK路徑重繞用以改進TCP效能的改良式AODV
論文名稱(外文):A Modified AODV with Ack-Path Traffic Rerouting for TCP Performance Improvement in Ad Hoc Wireless Networks
指導教授:許蒼嶺
指導教授(外文):Tsang-Ling Sheu
學位類別:碩士
校院名稱:國立中山大學
系所名稱:電機工程學系研究所
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:2004
畢業學年度:92
語文別:中文
論文頁數:50
中文關鍵詞:重繞斷線
外文關鍵詞:RerouteAd HocTCP performanceAODVRoute failure
相關次數:
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在本篇論文中,我們藉著修改Ad Hoc網路上的一個routing protocol,AODV (Ad Hoc On-Demand Distance Vector),來達成利用ACK路徑reroute的方法,並且將這個修正過的機制稱為MAODV (Modified AODV)。MAODV中增加幾個新的routing information,用來告知TCP網路上的情況。在route failure發生後,會在來源端monitor是否有目的地端來的ACK封包,如果有的話就用這ACK封包的資訊來更新routing table,使得TCP可以利用回傳的ACK路徑將資料傳出去。TCP利用回傳的ACK路徑開始傳送資料後,還必須處理因為斷線而丟掉的封包,因為這些丟掉的封包與網路壅塞造成的不同需要另外處裡,所以TCP在收到第1次duplicate ACK時就會重傳丟掉的封包,並且不會降下cwnd,直到因為route failure丟掉的封包都重傳完時,才回到原來TCP的機制。我們實際用NS來模擬,模擬的結果中可以看出,當斷線的位置在資料路徑的前端,也就是靠近來源端的地方,MAODV比起TCP-BuS (BUffering capability and Sequence information) 與原來的TCP都有較好的表現。因為此時AODV要重建路徑需要花很多的時間,尤其是來源端離目的地端的hops數越多的時候越顯的明顯,MAODV早就利用ACK的路徑將封包傳出去,而TCP-BuS與TCP都要等到路徑找好才能傳資料。至於斷線在資料路徑的後端的話,MAODV比起TCP-BuS和原來的TCP差別就不明顯。這是因為AODV會啟動local repair的功能,減少了找尋路徑的時間,在極端的狀況下,當local repair重試多次依然找尋不到路徑時,會返回到來源端重新尋找路徑,此時MAODV就可以看出效果。
In this thesis, a modified routing protocol, MAODV (Modified Ad Hoc On-Demand Distance Vector), is proposed for wireless Ad Hoc networks. MAODV uses ACK paths for rerouting data traffic whenever there is a route failure. We create new flags in the routing information of AODV to timely notify TCP layer the network status. After a route failure, the source node monitors ACK packets from the destination node. Every ACK packet when it is received from the destination node, its carried information is used to update the routing tables. Thus, without any interruption, TCP can take the reverse route of the ACK forwarding paths to continue to transmit the rest of data packets. In our proposed scheme, without decreasing the size of TCP congestion window (CWND), a lost packet can be immediately retransmitted as soon as the first duplicate ACK is received. We use NS-2 to simulate the proposed MAODV. From our simulation results, we have shown that when the position of route failures is near the source node, it may take more time to find new data paths. Hence, MAODV has the advantages by taking the reverse ACK paths to transmit data packets before new routing paths are found. Finally, we have demonstrated that MAODV performs better than TCP-BuS (BUffering capability and Sequence information) and the original TCP, when there are many hops between the source node and the destination node. On the other hand, when the position of route failures is near the destination node, the advantages of MAODV become not so significant because there exists some local repair mechanisms to be applied.
第一章 導論………………………..…………………………………………………1
1.1 研究動機…………….………..……………………………………….….…1
1.2 論文簡介…………………………………………………………………….1
1.3 論文架構…………………………………………………………………….3

第二章 Ad Hoc網路上改進TCP效能的相關研究……………….……..…………..4
2.1 Ad Hoc網路上的routing protocol介紹.……………………………………4
2.1.1 AODV的封包格式.…………..………………………………….…...4
2.1.2 AODV的路徑建立與維持…………………..……………………….5
2.2 在Ad Hoc網路上各種改進TCP效能的方法…..………….………………7
2.2.1 藉由routing information…….………….……………….…………...7
2.2.2 分辨Ad Hoc網路上不同的狀況…………………………..………..9
2.2.3 限制cwnd的大小…………………………………….……..……..11
2.2.4 將TCP分段………………………………………..……………….12
2.2.5 其他方法………………………………………..……….………….12
2.3 各個方法的比較…………………………………………………………...13
2.4 本論文的方法………………………..……………….………….….……..14

第三章 具有ACK路徑重繞的AODV…………………..…………………………15
3.1 修改AODV的部分…………….………………………..............………..15
3.2 修改TCP的部分……….…………………………………………………..17
3.3 MAODV完整的流程……………………………………………...……….18
3.4 MAODV的演算法………………………………………………..…….…22
第四章 模擬結果………………………………………………………..…….…….27
4.1 Ad Hoc網路模擬器…….…………………………………………..…..…..27
4.1.1 修改過的NS模組…………….…………………………….………27
4.1.2 新增加的NS模組…………….…………………………………….27
4.2使用者自訂的網路拓樸……………………..……………….……………29
4.2.1 結果分析………………………………………………..………….30
4.2.2 斷線在資料路徑的上游………………………………………….30
4.2.3 斷線在資料路徑的下游……………………………………...……35
4.3使用亂數產生的網路拓樸………………………………………………...38
4.3.1結果分析…………………………………….……………….…..….39

第五章 結論與未來工作……………………………………………………………41
5.1 結論………………………………………………………………………...41
5.2 未來工作………………………………………………………………...…42

Reference………………………………………..……………………………………43
Index………………………………………………………………………………….47
[1]C. Perkins, E. Belding-Royer, S. Das, “Ad hoc On-Demand Distance Vector (AODV) Routing”, IETF RFC 3561, July 2003.
[2]Dave Johnson, “The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR)”, http://www.ietf.org/internet-drafts/draft-ietf-manet-dsr-09.txt, Apr 2003.
[3]C.-K. Toh, “Long-lived Ad Hoc Routing based on the Concept of Associativity”, http://www.ietf.org/proceedings/99nov/I-D/draft-ietf-manet-longlived-adhoc-routing-00.txt, March 1999.
[4]Zhenghua Fu, Xiaoqiao Meng, Songwu Lu, “How bad TCP can perform in mobile ad hoc networks”, Seventh International Symposium on Computers and Communications, pp. 298 – 303, July 2002.
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[7]R. Prakash, M. Sahasrabudhe, “Modifications to TCP for improved performance and reliable end-to-end communication in wireless networks”, Wireless Communications and Networking Conference, pp. 938 – 942, Sept. 1999.
[8]Hong Man, “ENIC - an improved reliable transport scheme for mobile ad hoc networks, Dong Sun”, Global Telecommunications Conference, vol. 5, pp. 2852 – 2856, Nov. 2001.
[9]M. Sugano, M. Murata, “Performance improvement of TCP on a wireless ad hoc network”, Vehicular Technology Conference, vol. 4, pp. 2276 – 2280, April 2003.
[10]Jin-Hee Choi , See-Hwan Yoo , Chuck Yoo , “An enhancement scheme for TCP over mobile ad hoc networks” Vehicular Technology Conference, vol. 3, pp. 1522 – 1526, April 2003.
[11]Jin-Hee Choi, Chuck Yoo, “TCP-aware source routing in mobile ad hoc networks”, Eighth IEEE International Symposium on Computers and Communication, vol.1, pp. 69 – 74, June - July 2003.
[12]Dongkyun Kim, C.-K. Toh, Yanghee Choi, “TCP-BuS: improving TCP performance in wireless ad hoc networks”, IEEE International Conference on Communications, vol. 3, pp. 1707 – 1713, June 2000.
[13]J. Liu, S. Singh, “ATCP: TCP for mobile ad hoc networks”, IEEE Journal on Selected Areas in Communications, vol. 19, pp. 1300 – 1315, July 2001.
[14]M. Gunes, D. Vlahovic, “The performance of the TCP/RCWE enhancement for ad-hoc networks”, Seventh International Symposium on Computers and Communications, pp. 43 – 48, July 2002.
[15]Zhenghua Fu; B. Greenstein, Xiaoqiao Meng, Songwu Lu, “Design and implementation of a TCP-friendly transport protocol for ad hoc wireless networks”, 10th IEEE International Conference on Network Protocols, pp. 216 – 225, Nov. 2002.
[16]M. Gerla, K. Tang, R. Bagrodia, “TCP performance in wireless multi-hop networks”, Second IEEE Workshop on Mobile Computing Systems and Applications, pp. 41 – 50, Feb. 1999.
[17]M. Petrovic, M. Aboelaze, “Performance of TCP/UDP under ad hoc IEEE802.11”, 10th International Conference on Telecommunications, vol. 1, pp. 700 – 708, Feb. - March 2003.
[18]Z. Fu, P. Zerfos, H. Luo, S. Lu, L.Zhang, M. Gerla, “The impact of multihop wireless channel on TCP throughput and loss”, INFOCOM, vol. 3, pp. 1744 – 1753, March - April 2003.
[19]Kai Chen, Yuan Xue, K. Nahrstedt, “On setting TCP''s congestion window limit in mobile ad hoc networks”, IEEE International Conference on Communications, vol. 2, pp. 1080 – 1084, May 2003.
[20]Rui Jiang, V. Gupta, C.V. Ravishankar, “Interactions between TCP and the IEEE 802.11 MAC protocol”, DARPA Information Survivability Conference and Exposition, vol. 1, pp. 273 – 282, April 2003.
[21]IEEE 802.11 WG.IEEE Std Standard 802.11, 1999 edition International Standard [for] Information Technology-Telecommunications and Information Exchange between systems-Local and metropolitan networks. IEEE, 1999. http://standards.ieee.org/getieee802/802.11.html .
[22]A. Bakre, B.R. Badrinath, “I-TCP: Indirect TCP for Mobile Hosts”, Proceedings of the 15th International Conference on Distributed Computing Systems, pp. 136 – 143, June 1995.
[23]S. Kopparty, S.V. Krishnamurthy, M. Faloutsos, S.K. Tripathi, “Split TCP for mobile ad hoc networks”, Global Telecommunications Conference, vol. 1, pp. 138 – 142, Nov. 2002.
[24]Haejung Lim, Kaixin Xu, M. Gerla, “TCP performance over multipath routing in mobile ad hoc networks”, IEEE International Conference on Communications, vol. 2, pp. 1064 – 1068, May 2003.
[25]C.D.A. Cordeiro, S.R. Das, D.P. Agrawal, “COPAS: dynamic contention-balancing to enhance the performance of TCP over multi-hop wireless networks”, Eleventh International Conference on Computer Communications and Networks, pp. 382 – 387, Oct. 2002.
[26]The Network Simulation ns-2, http://www.isi.edu/nsnam/ns/
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