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Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks

Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks. Zhi-Li Zhang, Yuewei Wang, David H. C. Du, Dongli Su IEEE/ACM TRANSACTIONS ON NETWORKING, AUGUEST 2000. Outline. Introduction Video Staging: A Single Video Case without Smoothing

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Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks

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  1. Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks Zhi-Li Zhang, Yuewei Wang, David H. C. Du, Dongli Su IEEE/ACM TRANSACTIONS ON NETWORKING, AUGUEST 2000

  2. Outline • Introduction • Video Staging: A Single Video Case • without Smoothing • with Smoothing • Empirical Evaluation • Video Staging: Multiple Video Case • Staging Hot Video Only(SHVO) • Largest Bandwidth Reduction Ratio First(LBRRF) • Empirical Evaluation • Conclusion

  3. Introduction • Video Staging • Reduce the bandwidth requirement in the Backbone WAN • Prefetch a predetermined amount of video data and store them a priori at proxy servers • Only part of a video stream is retrieved directly from the central video server across the backbone WAN

  4. Video Staging(cont.) • Trading the disk bandwidth of a proxy server for the backbone WAN bandwidth • The video data are staged at the proxy server on a fairly long period of time instead of caching in and purged out dynamically

  5. Video Staging:A Single Video Case • Video Staging Without Smoothing i : the index of a video Ni: total number of frames F : frame period sij : the size of jth frame j = 1,…, Ni Pi : the peak rate of video i Pi = (max1<=j<=Nisij) /F Ci : cut-off rate 0 <= Ci <=Pi*F = max1<=j<=Nisij

  6. Video Staging Without Smoothing • The upper part consists of a sequence of partial frames with size sij ,u = (sij - Ci )+ j = 1,…, Ni where x+ = max{x,0} • The lower part consists of a sequence of partial frames with size sij ,l = sij - (sij - Ci )+j = 1,…, Ni

  7. Video Staging Without Smoothing • The smaller Ci is,the more video data is staged at a proxy server. • As Ci decreases, the lower part of the video becomes less bursty, and eventually approaches to an essentially CBR stream. • The backbone WAN bandwidth requirement from Pi to Ti = Ci / F • The upper part of the video consume Di = (max1<=j<=Nisij,u) / F disk bandwidth • Bandwidth reduction ratio Ri = (Pi -Ti) / Di

  8. Video Staging With Smoothing • Cut-Off After Smoothing (CAS) si~j : referred to as smoothed framessize Pi : the peak rate of smoothed stream Ci : cut-off rate 0 <= Ci <=Pi*F = max1<=j<=Nisi~j Ti = Ci / F amount of backbone WAN bandwidth is reserved Di= (max1<=j<=Nisi~j,u) / F amount of disk bandwidth is required in the worst case

  9. Video Staging With Smoothing • Cut-Off Before Smoothing • Smoothing on the Lower Part(SOLP) Ti = Pi =(max1<=j<=Nisi~j,l) / F • Smoothing on the Upper Part(SOUP) • Reduce the disk bandwidth required • Smoothing on the Upper and Lower Parts(SOLP) Bl = B * (Ci / Pi * F) Bu = B * (1- (Ci / Pi * F))

  10. Proxy server disk resource requirements for a single stream

  11. Resource requirements for a single stream

  12. Ratio of backbone WAN bandwidth reduction to proxy server disk bandwidth

  13. Video Staging: Multiple Video Case • Disk bandwidth • Total amount of storage space • The number of expected concurrent accesses • Total reduction in the backbone WAN bandwidth is maximized • Disk bandwidth constraint • Disk storage constraint

  14. Staging Hot Video Only (SHVO) • Regard the user access pattern as the most important factor in determining which video to stage at the proxy server. • The videos are ordered with respect to their relative “popularity” • The number of k hottest videos that can be staged at the proxy server is determined • Either a video is entirely staged at the proxy server or not at all

  15. Largest Bandwidth Reduction Ratio First (LBRRF) • Use the backbone WAN bandwidth reduction ratio Ri in determining which video and what percentage of it to be staged • The burstier video and the video with larger number of concurrent accesses is more likely to have a higher Ri • CPi percentage of video i is staged at the proxy server • The algorithm starts with CPi = 0 for all videos and iterates by incrementing CPi by P amount at each step.

  16. Impact of proxy server disk resources:clients have no smoothing buffer

  17. Impact of proxy server disk resources:clients have 64KB smoothing buffer

  18. Conclusion • A major objective of our approach is to reduce the backbone WAN bandwidth requirement. • We have designed various video staging methods and evaluated their effectiveness in trading the disk bandwidth of a proxy server for the backbone WAN bandwidth. • The proposed proxy-server-based video staging technique provides a cost-effective and scalable solution to the problem of the end-to-end video delivery over WANs.

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