伴隨著網路頻寬的增長及人們對於多媒體影音串流的需求增加，多媒體影音服務變得熱門且成為一個網際網路的重要應用。傳統的主從式網路架構因成本考量無法支援大量的使用者，而限制了系統能服務的規模。點對點式的傳輸架構因具有能減少伺服器端頻寬流量的特點，因此被廣泛應用在許多的多媒體即時影音串流服務上以支援大量的使用者人數。
在VUD 點對點式串流系統下，可有效縮短傳統網狀拓撲造成頻道切換延遲的時間，但當大量使用者短時間內湧入系統的情況發生時，將會使得整體系統的串流傳輸效率不彰，而延長使用者的頻道切換時間。
本論文針對VUD 點對點式串流系統在大量使用者湧入系統的情境下，提出以資源考量的速率控制機制限制使用者進入系統的數量，使系統即使在大量使用者湧入系統的情況下，不會因使用者之間彼此爭奪有限的上傳頻寬資源，而延長頻道切換延遲時間。與尚未加入存取控制的VUD點對點式串流系統比較，模擬結果顯示了我們所提機制的有效性。

With the increasing network bandwidth and demand of multimedia streaming, multimedia services are getting popular and important on the Internet. Traditional client/server model cannot afford to support a large number of users because of cost consideration. Therefore, the service scale is limited. One characteristic of P2P architecture is that it can reduce the bandwidth consumption at server side, so it has been widely applied on many multimedia live streaming services to serve the large number of users.
VUD P2P streaming system can effectively reduce the channel switching delay compared to tradition mesh-based overlay. However, while a large number of users join the system in a short period of time, this situation will cause the competition of network upload bandwidth, thus decreasing the transmission performance of the whole system, and increasing the user’s channel switching delay, accordingly.
In this thesis, we propose a resource-aware flash-crowd control mechanism for controlling the access rate when flash crowd occurs under the VUD P2P streaming system. Even in the case that a large number of users want to enter the system, they do not compete for the limited upload bandwidth among themselves and thus no excessive channel switching delays occur. Comparison with the VUD P2P streaming system without added access control mechanism, simulation results show the effectiveness of our proposed mechanism.

[1] X. Zhang, J. Liu, B. Li, T. P. Yum, “DONet/CoolStreaming: A Data-Driven Overlay Network for Peer-to-Peer Live Media Streaming,” IEEE International Conference on Computer Communications (INFOCOM), pp.2102-2111, Mar. 2005.
[2] PPTV [Online]. Available: http://www.pptv.com
[3] PPStream [Online]. Available: http://www.ppstream.com
[4] X. Su, S. K. Dhaliwal, “Incentive Mechanisms in P2P Media Streaming Systems,” IEEE Internet Computing, vol.14, no.5, pp.74-81, Sept. 2010.
[5] D. Wu, C. Liang, Y. Liu, K. Ross, “View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems,” IEEE International Conference on Computer Communications (INFOCOM), pp. 2726-2730, Apr. 2009.
[6] S.M.Y. Seyyedi, B. Akbari, “Hybrid CDN-P2P Architectures for Live Video Streaming: Comparative Study of Connected and Unconnected Meshes,” Computer Networks and Distributed Systems (CNDS), 2011 International Symposium on, pp175-180, Feb. 2011.
[7] I. Baumgart, B. Heep, S. Krause, “OverSim: A scalable and flexible overlay framework for simulation and real network applications,” IEEE Peer-to-Peer Computing. pp. 87-88, Sept. 2009.
[8] Video trace file [Online]. Available: http://www2.tkn.tu-berlin.de/research/trace/ltvt.html
[9] J. Sugih, P.B. Danzig, S.J. Shenker, L. Zhang, “A measurement-based admission control algorithm for integrated service packet networks, “ IEEE/ACM Transaction on Networking, vol.5, no.1, pp.56-70, Feb. 1997.
[10] S. Ratnasamy, M. Handley, R. Karp, S. Shenker, “Application-Level Multicast Using Content-Addressable Networks,” Networked Group Communication, Third International COST264 Workshop, pp.14-29 , 2001.
[11] B. Suman, B. Bobby, K. Christopher, “Scalable Application Layer Multicast,” Proceeding of ACM SIGCOMM, vol.32, no.4, pp.205-217, Oct. 2002.
[12] Planet lab [Online] Available: http://www.planet-lab.org
[13] X. Hei, C. Liang, J. Liang, Y. Liu, K.W. Ross. “A Measurement Study of a Large-Scale P2P IPTV System,” IEEE Transaction on Multimedia, vol.9, no.8, pp.1672-1687, Dec. 2007.
[14] Y. Chen, C. Chen, “Modeling and Performance Analysis of P2P Live Streaming Systems under Flash Crowds,” IEEE International Conference on Communications(ICC), pp.1-5, Jun. 2011.
[15] C. Liang, Y. Liu, “ViVUD: Virtual Server Cluster based View-Upload Decoupling for Multi-Channel P2P Video Streaming Systems,” IEEE Global Telecommunications Conference (GLOBECOM), pp1-5, Dec. 2010.
[16] B. Li, G.Y. Keung, S. Xie, F. Liu, Y. Sun, H. Yin, “An Empirical Study of Flash Crowd Dynamics in a P2P-Based Live Video Streaming System,” IEEE Global Telecommunications Conference(IEEE GLOBALCOM), pp.1-5, Dec.4 2008.
[17] N. Magharei, R. Rejaie, Y. Guo, “Mesh or Multiple-Tree: A Comparative Study of Live P2P Streaming Approaches,” IEEE International Conference on Computer Communications (INFOCOM), pp.1424-1432, May 2007.
[18] X. Hei, Y. Liu, and K. Ross, “Inferring Network-Wide Quality in P2P Live Streaming Systems,” IEEE Journal on Selected Areas in Communications, vol.25, no.9, pp.1640-1654, Dec. 2007.
[19] F. Liu, B. Li, L. Zhong, B. Li, “Understanding the flash crowd in P2P Live Video Streaming Systems,” IEEE Proc. in Packet Video Workshop, pp. 1-10, May 2009.
[20] B. Li, G. Y. Keung, X. Zhang, “Coolstreaming: Design, Theory, and Practice,” IEEE Transactions on Multimedia, vol. 9, no. 8, pp. 1661-1671, Dec. 2007
[21] D. Wu, C. Liang, Y. Liu, K. Ross, “Redesigning multi-channel P2P live video systems with View-Upload Decoupling,” Computer Networks, vol. 54, no. 12, pp. 2007-2018, Aug. 2010