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「串流代理伺服器平台」之設計與實做. Design and Implementation of a Streaming Proxy Server Platform for Internet Video Streaming. 國科會自由軟體專案計 畫 ( NSC 94-2218-E-020-002 ). 國立屏東科技大學資訊管理系 童曉儒 2006/11/ 1 0. Outline. Background Design goals Segment-based Caching Schemes
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「串流代理伺服器平台」之設計與實做 Design and Implementation of a Streaming Proxy Server Platform for Internet Video Streaming 國科會自由軟體專案計畫(NSC 94-2218-E-020-002) 國立屏東科技大學資訊管理系 童曉儒 2006/11/10
Outline • Background • Design goals • Segment-based Caching Schemes • Architecture of Streaming Proxy Server (SPS) • Experimental Results • Conclusion
Background • Internet video streaming: • Challenges: Significant WAN delay jitter and unstable throughput. • Current implementation: No proxy, large client buffering/ long initial delay. • Proxy-assisted video streaming • Segment-based caching • Reducing initial delay • Reducing WAN traffic by locally sharing videos.
Background (Contd.) Proxy-assisted video streaming
Design Goals • Streaming Proxy Server (SPS) • Web compatible: user transparent (web server, media player, Http1.1). • Configurable: provide generic modules which can be configured into different segment-based caching schemes. • LAN-stream/WAN-segment hybrid transmission control: provide stable stream quality. • Two-year project: • First year: unicast-based approach (94). • Second year: unicast/multicast hybrid approach (95).
Segment-based Caching • Two schemes were implemented. • Prefix Caching： • Video prefix is cached in SPS. • Upon request, SPS first sends video prefix to clients. • SPS then retrieves video suffix from the server. • Reducing initial waiting time. • Suffix-Window caching (proposed by us)： • SPS further dynamically caches a window of video suffix for each video stream. • Other clients requesting the same video will first check the suffix-window segments available in SPS before asking the video suffix from the server. • Video sharing -> reduce WAN traffic.
System Architecture of SPS • Three modules:Storage management subsystem (SMS), Caching policy subsystem (CPS), flow control subsystem (FCS). System Architecture of SPS
System Architecture- SMS • Performance monitoring interface. • System configuration interface. • HTTP Connection management. • Cache resource management.
System Architecture- CPS • Defining configuration parameters. • Defining caching policy. • Caching policies management
System Architecture- FCS • Stream flow controller: • Streaming between client and SPS. • Fine-grained datagram. • Segment-based flow controller: • Segment file retrieval between SPS and server • Coarse-grained segment. • ATCP+ (proposed by us)
Adaptive TCP-Trunking Flow Control(ATCP+) • A segment is divided into K sub-segments. • K sub-segments are download in parallel by using Multi-Thread Download mechanism. • K is dynamically adjusted subject to the sustainable network throughput. Single-thread download Multi-thread download
Experimental Result- Functional test • SPS hardware: CPU P-Dual 2.8GHz, 1024M RAM, SATA HDD, • SPS software: Window XP, Java
Experimental Result- Performance test • Random access of 5 X 1.5-bps MPEG-1 videos by increasing client numbers under WAN or LAN. • Performance metrics: • Initial delay. • Sustainable throughput. • K value. • Pressure test.
Initial Delay- LAN 區域網路initial delay圖
Initial Delay- WAN 廣域網路initial delay圖
Pressure Test Result Scheme
Conclusion • SPS provides a platform which can be flexibly configured according to different segment-based caching schemes. • Two novel features are proposed and implemented • Suffix-window caching: achieves efficient video sharing particularly under an intensive video access environment (like new-on-demand). • ATCP+: provides a stable network throughput. • Experiment result shows SPS with suffix-window running on a PC Pentium-Dual 2.8GHz can support over 50 concurrent MPEG-1 video accesses.
