多媒體串流一般是透過傳輸層協定來傳遞，像是TCP或UDP，跟UDP協定做比較，TCP協定雖然可以保證資料的可靠性，但為了確保資料的完整性，所以增加了整體傳輸的時間。IETF(Internet Engineering Task Force)在2000年制定了一個新的傳輸層的通訊協定稱做SCTP (Stream Control Transmission Protocol)，跟TCP協定一樣具有可靠的特性，但其又具有多宿主(multi-homing)的特性，SCTP改善了關連(association)的可靠度，當主要的傳輸路徑發生錯誤時可將資料切換到其它的路徑上傳遞。此外，SCTP在2004年提出了不完全可靠度傳輸(partial reliable)的延伸，稱為PR-SCTP，此協定可以設定訊息傳遞的存活時間，因此更適合用來傳遞即時的多媒體串流。
本論文提出結合多宿主和PR-SCTP的特性，當兩個端點間有多條路徑的情況下，會選擇一條當作主要的傳輸路徑和一條當作修復路徑來傳遞備援的資料。因為我們所傳遞的多媒體串流是MPEG-4的格式，所以備援的資料內容是對於影像撥放較重要的I-frame；最後，本研究主要是利用網路模擬工具NS-2，來比較我們的方法和原始的PR-SCTP傳遞多媒體串流的PSNR值，從模擬結果可以看出，我們的方法可以改善主要路徑上的封包遺失而導致影片品質下降的現象以及當主要路徑斷線的時候，可以藉由修復路徑上的備援資料來維持影片的品質。

Multimedia streaming is generally transmitted by the transport layer protocol, e.g., TCP and UDP. Compared to UDP, TCP protocol guarantees the reliability of data but increases overall transmission time to make sure the integrity of data. In 2000, IETF sets up a new transport layer protocol called SCTP. With the same reliability as TCP and the characteristics of multi-homing, SCTP enhances the stability of connection by switching data to other transmission paths when errors or losses occur in the main path. In addition, the partial reliable extension called PR-SCTP is added into SCTP in 2004, which is capable of setting the TTL(time to live) of data transmission. Therefore, it is more appropriate for real-time multimedia transmission.
The proposed mechanism combining the characteristics of multi-homing and PR- SCTP will choose a main transmission path and a repairing one to send back- up data when several paths are built between two endpoints. Because the format used in multimedia streaming is MPEG-4, the content of back-up data is just I-frame, which is most important for video playing. At last, the network simulation tool NS-2 is used to compare the proposed method with that of original PR-SCTP in multimedia transmission in terms of the PSNR values. From the simulation results, the loss of packets in main path will not lead to the decline of video quality and the lost data in the broken main path is successfully restored by the back-up data in the repair path, thus the quality of video is retained.

[1] D. Wu, Y. Hou, W. Zhu, Y.-Q. Zhang, and J. Peha, "Streaming Video over the Internet: Approaches and Directions" , IEEE Transactions on Circuits and Systems for Video Technology, March 2001.
[2] S. Blake et al., "An Architecture for Differentiated Services," IETF RFC 2475, Dec. 1998.
[3] International Telecommunications Union Study Group 17, URL: http://www.itu.int/ITU-T/studygroups/com17/index.asp, May 2003.
[4] DSL Forum Report, Global DSL Subscribers Now Total 73.4 Million, Website - http://www.dslforum.org
[5] R. Doverspike et al., "Designing a Reliable IPTV Network", IEEE Internet Computing, vol. 13, pp. 15-22, 2009
[6] Z. Lifen, S. Yanlei and L. Ju, "The Performance Study of Transmitting MPEG4 over SCTP", in the proc. of IEEE Int. Conf. Neural Networks & Signal Processing, pp. 1639-1642, December 2003.
[7] IETF RFC 2960: Stream Control Transmission Protocol (2000)
[8] 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 no. 2, pp. 1-14, 1989.
[9] Stewart, R., Ramalho, M., Xie, Q., et al.: Stream Control Transmission Protocol (SCTP) Partial Reliability Extension. IETF RFC 3758 (2004)
[10] ISO CD11172-2: Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to 1.5 Mbits/s, Nov. 1991. MPEG.
[11] Caro, A, Amer, P, Stewart, R, "Rethinking End-to-End Failover with Transport Layer Multihoming", Annals of Telecommunications 2006
[12] Grace, K.H., Pecelli, D., Amelia, J.D.: Improving Multi-homed SCTP Mobile Communication Performance. Technical Papers, The MITRE Corporation (2006)
[13] Qiao, Y., Fallon, E., Murphy, L., et al.: Performance Analysis of Multi-homed Transport Protocols with Network Failure Tolerance. IET Communications 5(2), 336–345 (2007)
[14] H. Wang, Y. Jin and W. Wang, "The performance Comparison of PRSCTP, TCP and UDP for MPEG-4 Multimedia Traffic in Mobile Network", in the proc. Of ICCT 2003, pp. 403-406.
[15] M. Molteni and M. Villari "Using SCTP with Partial Reliability for MPEG-4 Multimedia Streaming", BSDCon Europe 2002
[16] XU, C. et al. Comparative study of real-time multimedia transmission over multi-homing transport protocols. In: 11th IFIP/IEEE International Conference on Management of Multimedia and Mobile Networks and Services (MMNS), 2008. Springer LNCS (Lecture Notes in Computer Science), p. 64–76.
[17] J. Iyengar, K. Shah, P. Amer, and R. Stewart, "Concurrent multipath transfer using SCTP multihoming", presented at the SPECTS’04 Conf., San Jose, CA, Jul. 2004.
[18] The Network Simulation -ns-2 http://www.isi.edu/nsnam/ns/index.html
[19] J. Klaue, B. Rathke, and A. Wolisz, "Evalvid—a framework for video transmission and quality evaluation", in Proc. 13th Int. Conf. Modeling Techniques and Tools for Computer Performance Evaluation, Urbana, IL, Sep. 2003.