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    Please use this identifier to cite or link to this item: https://nccur.lib.nccu.edu.tw/handle/140.119/49478


    Title: 利用可變速率方法賦予網路電話壅塞控制能力
    Congestion Control Enabled VoIP by Flexible Bit-rate
    Authors: 丁諭祺
    Ting, Yu Chi
    Contributors: 連耀南
    Lien, Yao Nan
    丁諭祺
    Ting, Yu Chi
    Keywords: 壅塞控制
    可變速率
    數據壅塞控制協定
    網路電話
    Congestion Control
    Flexible Bit-rate
    DCCP
    VoIP
    Date: 2010
    Issue Date: 2010-12-08 12:13:00 (UTC+8)
    Abstract: 近年來，一個具有壅塞控制機制的傳輸協議DCCP被提出，期能取代UDP成為不可靠傳輸的主流協議。我們以NS-2網路模擬器和實際網路進行實驗，發現DCCP無法與其他傳輸協議公平分享頻寬，因此現行DCCP的設計，尚無法完全取代UDP。此外，目前DCCP以調整封包間隔的方式進行壅塞控制，也不適用於講求時效性的網路服務。
    本研究首先以實驗證明，當網路情況不佳時，DCCP無法與其他傳輸協議公平的分享頻寬；當使用DCCP傳輸越洋長距離網路電話，如遇頻寬不足時，會因頻寬競爭力較弱而無法維持通話品質。本研究提出可變速率方法(Flexible Bit-rate)調整時效性網路服務的封包大小來進行壅塞控制，在維持一定服務品質之前提下，促進網路的和諧。我們在一個實際網路的實驗環境中評估以UDP、DCCP及可變速率三種方式傳輸網路電話封包的效能，結果顯示透過可變速率方法，能有效降低網路電話的封包遺失率，維持通話品質。
    With congestion-control ability, Datagram Congestion Control Protocol (DCCP) is expected to replace UDP as a mainstream unreliable transport protocol. But our study found that DCCP is not able to get a fair share of bandwidth under the competition of others transport protocols no matter in NS-2 simulation or real world networking environments. Furthermore, any congestion control protocol that postpones the transmission of packets may not be adequate to support time-sensitive network services.
    To maintain the quality of time-sensitive network services as well as to be TCP-friendly when facing network bandwidth fluctuation, we propose a Flexible Bit-rate congestion control mechanism for VoIP to adjust their data rate. Our experiments show that Flexible Bit-rate congestion control method could effectively reduce the packet loss rate and to maintain VoIP quality as compared with UDP and DCCP. Furthermore, it can have a much better bandwidth efficiency and adjust better to network fluctuation.
    Reference: [1] C. Albuquerque, B.J. Vickers, and T. Suda, "Network border patrol: Preventing congestion collapse and promoting fairness in the Internet," IEEE-ACM Transactions on Networking, vol. 12, no. 4, Dec. 2004, pp. 173-186.
    [2] L. S. Brakmo, S. W. O’Malley, and Larry L. Peterson. "TCP Vegas: New Techniques for Congestion Detection and Avoidance," ACM SIGCOMM, Aug. 1994, pp. 24-35.
    [3] D. Chiu and R. Jain, "Analysis of the Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks," Computer Networks and ISDN Systems, vol.1, 1989, pp. 1-14.
    [4] A. Falk, D. Katabi, Y. Pryadkin," Specification for the Explicit Control Protocol (XCP)," draft-falk-xcp-03.txt (work in progress), July 2007.
    [5] K. Fall and S. Floyd, "Simulation-based Comparisons of Tahoe, Reno, and SACK TCP," ACM Computer Communication Review, vol. 26, no.3, 1996, pp. 5-21.
    [6] S. Floyd and T. Henderson, "The NewReno Modification to TCP`s Fast Recovery Algorithm," IETF RFC 2582, 1999.
    [7] S. Floyd and E. Kohler, "Profile for DCCP Congestion Control ID 2: TCP-like Congestion Control," IETF draft-ietf-dccp-ccid2-08, http://www.ietf.org/internet-drafts/draft-ietfdccp-ccid2-10.txt, Mar. 2005.
    [8] S. Floyd, E. Kohler, and J. Padhye, "Profile for DCCP Congestion Control ID 3: TFRC Congestion Control," IETF draft-ietf-dccp-ccid3-11, http://www.ietf.org/internetdrafts/draft-ietf-dccp-ccid3-11.txt, Mar. 2005.
    [9] Z. Fu, P. Zerfos, H. Luo, S. Lu, L. Zhang, and M. Gerla, "The impact of multihop wireless channel on TCP throughput and loss," IEEE INFOCOM, San Francisco, CA, March 2003.
    [10] Eddie Kohler, Mark Handley, and Sally Floyd, "Designing DCCP: Congestion Control Without Reliability," SIGCOMM 06, Sep. 2006, Pisa, Italy, pp. 27-38.
    [11] V. Jacobson, "Congestion Avoidance and Control," ACM SIGCOMM, Aug. 1988, pp. 314-329.
    [12] N. E. Mattsson, "A DCCP module for ns-2," http://epubl.luth.se/1402-1617/2004/175/LTU-EX-04175-SE.pdf, Sep. 2004.
    [13] J.Nagle, "Congestion Control in TCP/IP," RFC896, Jan 1984.
    [14] K. Nahm, A. Helmy, and C.-C J. Kuo, "TCP over Multihop 802.11 Networks: Issues and Performance Enhancement," ACM MobiHoc 05, Urbana-Champaign, Illinois, USA, May 2005.
    [15] F. Sabrina and J.-M. Valin,"Adaptive Rate Control for Aggregated VoIP Traffic," GLOBECOM 2008, pp. 1405-1410.
    [16] W. Stevens, "TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery Algorithms," IETF RFC 2001, 1997.
    [17] The E-Model, http://www.itu.int/rec/T-REC-G.107.
    [18] "The Network Simulator - ns-2", http://www.isi.edu/nsnam/ns/.
    [19] G.723, http://www.itu.int/rec/T-REC-G.723/e.
    [20] G.729, http://www.itu.int/rec/T-REC-G.729/e.
    [21] iLBC, http://www.ietf.org/rfc/rfc3951.txt.
    [22] Mean Opinion Score, http://en.wikipedia.org/wiki/Mean_opinion_score.
    [23] SpeeX, http://www.speex.org/.
    Description: 碩士
    國立政治大學
    資訊科學學系
    97753014
    99
    Source URI: http://thesis.lib.nccu.edu.tw/record/#G0977530141
    Data Type: thesis
    Appears in Collections:[Department of Computer Science ] Theses

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