視訊傳播不啻為當今最熱門的網路應用，使用者藉由網路從遠端的伺服器接收視訊或影片。一些著名的視訊傳播系統，例如NICE、ZIGZAG、PALS…等，各針對不同的使用需求，實況轉播或是隨選視訊(video on demand)，而發展出因應的傳輸機制。
隨選視訊讓使用者能讓任意時間點選喜愛的影片觀賞，然而傳統的點對點(point to point)主從式(server-client)的傳輸機制，雖然能提供這樣的服務，然而浪費大量頻寬及儲存空間，反限制了系統的規模。藉由群播(multicast)觀念而發展的傳輸機制，例如:batching、patching、chaining …等，不但能減輕伺服器的負擔，也節省網路頻寬及儲存空間。其中optimal chaining利用客戶端buffer共享的觀念，使得整體buffer的使用效率最佳化，進而達到使伺服器的流出串流數(outgoing streams)能減到最少。此外，由於使用者資源，例如：頻寬、儲存空間、運算能力…等的差異性，層狀編碼(layered coding)亦應運而生，一份原始資料可以解碼出不同位元率(bit-rate)的影片，提供各種使用者觀賞適合的影片。
本文提出適合層狀編碼視訊的傳輸機制。基於optimal chaining的傳輸機制，再加以代理伺服器（proxy）的輔助，用以傳播層狀編碼的視訊串流。不僅能減輕伺服器和網路的負擔，也能讓資源差異的使用者都能夠觀賞相對應品質的影片。

Large-scale VOD system is a promising Internet service in current and next generation. However, traditional VOD system is insufficient to satisfy each client’s requirement due to the asynchrony and heterogeneity of client devices and limited system resource for serving large scale of unpredictable requirements. Besides, the multicast service is not globally available due to the deployment of network layer multicast and interoperability.
Application layer multicast techniques are proposed to solve the problem. ZIGZAG is a peer-to-peer technique for single-source media streaming which allows the server to distribute the content to many clients by constructing a multicast tree and organizing the clients into an appropriate tree rooted at server. It also avoids the network bottleneck by reducing the processing hops on the delivery path to a client. NICE is a scalable application layer multicast protocol, specially designed for low bandwidth, data streaming applications with large receiver sets, such as real-time news, sports games, on-line radios. e.g... The NICE protocol arranges the peers into a hierarchy and creates a hierarchically-connected control topology. It can reduce the control overhead of the structure over which the data delivery paths are built. PALS is receiver-driven peer-to-peer scheme for on-demand streaming with quality adaptive playback for layer encoded streaming media which allows a receiver to orchestrate the adaptive delivery of stored layer encoded streams from multiple sender peers.
Regional proxy caching reduces both network and server loads, as well as client start-up latency by caching video content at proxy servers. Chaining based schemes provide another means of reducing network bandwidth by using client as surrogate servers for parts of videos.
In this thesis, we propose the layered chaining scheme based on optimal chaining as well as layered coding techniques. It can not only reduce the server load but also satisfy the clients’ request. Moreover, by adding in the capability of proxy on the streaming delivery platform, every video streaming chain becomes more reliable, available, fully utilized. As shown in the simulation results, our layered chaining scheme achieves better performance in overall reject rate comparing to the non-scalable chaining approach. Moreover, the system resources including server bandwidth as well system buffer are fully utilized and optimized.

[1]. S. H. G. Chan, F. Tobagi, and T. M. Ko, “Providing on-demand video services using request batching,” in IEEE Int. Conf. Communication, vol. 3, 1998, pp. 1716–1722.
[2]. C. Aggarwal, J. Wolf, and P. Yu, “On optimal batching policies for video-on-demand storage servers,” in Proceedings of IEEE International Conference on Multimedia Computing and Systems, Jun. 1996.
[3]. K. A. Hua, Y. Cai, and S. Sheu, “Patching: A multicast technique for true video-on-demand services,” in Proceedings of ACM Multimedia Conf., Bristol, U.K., Sep. 1998.
[4]. S. Viswanathan and T. Imielinaki, “Metropolitan area video-on-demand service using pyramid broadcasting,” in ACM Multimedia System., vol. 4, no. 4, Aug. 1996, pp.197–208.
[5]. L-S. Juhn and L-M. Tseng, “Fast broadcasting for hot video access,” in RTCSA’ 97: the proceedings of the 4th international workshop on real-time computing systems and applications, Oct. 1997, pp.237-243.
[6]. L-S. Juhn and L-M. Tseng, “Harmonic broadcasting for video-on-demand service,” IEEE Transactions on Broadcasting, vol. 43, no.3, Sep. 1997, pp. 268-271.
[7]. Yang-Hua Chu, Sanjay G. Rao, and Hui Zhang, “A case for end system multicast,” in ACM SIGMETRICS, 2000, pp. 1–12.
[8]. S. Banerjee, B. Bhattacharjee and C. Kommareddy, “Scalable Application Layer Multicast,” in Proceedings of ACM SIGCOM, Aug. 2002.
[9]. Tran, D.A., Hua, K.A.; Do, T., “ZIGZAG: an efficient peer-to-peer scheme for media streaming,” in Twenty-Second Annual Joint Conference of the IEEE Computer and Communications Societies, vol.2, Apr. 2003, pp.1283 – 1292.
[10]. Reza Rejaie and Antonio Ortega, “PALS: Peer-to-Peer Adaptive Layered Streaming,” in NOSSDAV’03, Conference of the Network and Operating System Support for Digital Audio and Video, Jun. 2003.
[11]. Subhabrata Sen, Jennifer Rexford, and Don Towsley,” Proxy prefix caching for multimedia streams,” in Proceedings of the Conference on Computer Communications, New York, Mar.1999.
[12]. J. Almeida, D. Eager, and M. Vernon, “A hybrid caching strategy for streaming media files,” in Proceedings of SPIE/ACM Conference on Multimedia Computing and Networking, Jan.2001.
[13]. D. Eager, M. Ferris, and M. Vernon, “Optimized regional caching for on-demand data delivery,” in Proceedings of Multimedia Computing and Networking, Jan. 1999.
[14]. Simon Sheu, Kien A. Hua, W. Tavanapong, “Chaining: a generalized batching technique for video-on-demand systems,” in proceedings of IEEE International Conference on Multimedia Computing and Systems, 1997, pp.110 –117.
[15]. Kien A. Hua, Simon Sheu, James Z. Wang, “Earthworm: A Network Memory Management Technique for Large-Scale Distributed Multimedia Applications,”in Proceedings of Sixteenth Annual Joint Conference of the IEEE Computer and Communications Societies, vol. 3, 1997, pp. 990-997.
[16]. Jen-Kai Chen and Jean-Lien C. Wu, “Adaptive Chaining Scheme for Distributed VOD Applications,” IEEE Transactions on Broadcasting, vol. 45, no. 2, Jun. 1999, pp. 215 - 224.
[17]. Te-Chou Su, Shih-Yu Huang, Chen-Lung Chan, Jia-Shung Wang, “Optimal chaining and implementation for large scale multimedia streaming,” in Proceedings of IEEE International Conference on Multimedia and Expo.,vol.1, Aug. 2002, pp.385 – 388.
[18]. Weiping Li, “Overview of fine granularity scalability in MPEG-4 video standard,” IEEE Transactions on Circuits and Systems for Video Technology, vol.11, no.3, Mar.2001, pp.301 - 317.
[19]. Wei-Hsiu Ma; Du, D.H.C., “Reducing bandwidth requirement for delivering video over wide area networks with proxy server,” in Proceedings of IEEE International Conference on Multimedia Computing and Systems, vol. 2, 2000, pp.991-994.
[20]. Kangasharju, J., Hartanto, F.; Reisslein, M.; Ross, K.W., “Distributing layered encoded video through caches,” IEEE Transactions on Computers, vol.51, Jun. 2002, pp.622 – 636.
[21]. Yi Cui, Klara Nahrstedt, “Layered peer to peer streaming,” International Workshop on Network and Operating System Support for Digital Audio and Video, 2003, pp.162 – 171.
[22]. Wang, B., Sen, S. ,Adler, M. ,Towsley, D., “Optimal Proxy Cache Allocation for Efficient Streaming Media Distribution,” IEEE Transactions on Multimedia, vol.6, Apr. 2004, pp.366 – 374.
[23]. R. Tewari, H. M. Vin, A. Dan, and D. Sitaram, “Resource based caching for Web servers,” in Proceedings of SPIE/ACM Conference on Multimedia Computing and Networking, Jan. 1998.
[24]. Philippe de Cuetos, Keith W. Ross, “Adaptive Rate Control for Streaming Stored Fine­Grained Scalable Video,” in NOSSDAV’02, Conference of the Network and Operating System Support for Digital Audio and Video, May 2002.