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Proxy-based Distribution of Streaming Video over Unicast ... Presentation Transcript

  • 1. Proxy-based Distribution of Streaming Video over Unicast/Multicast Connections B. Wang, S. Sen, M. Adler and D. Towsley University of Massachusetts Presented by Nera Liu
  • 2. Agenda
    • Introduction
    • Problem Setting and Model
    • Optimal Proxy Cache Allocation
    • Proxy-Assisted Transmission Schemes
    • Performance Evaluation
    • Conclusion
  • 3. Introduction
    • With the emergence of broadband network, streaming video over the Internet becomes feasible nowadays.
    • However, due to its high bandwidth and large client requirement, it is inefficient in traditional VoD system i.e. unicast-based system.
  • 4. Introduction
    • In designing scalable and cost effective VoD system, researchers mainly focused on two different approaches
      • Open-loop architectures
        • System performance is independent of system load
        • It achieves better performance under heavy system load
      • Closed-loop architectures
        • System performance is dependent of system load
        • It achieves better performance under light system load.
  • 5. Introduction
    • Assumption of previous works
      • It is designed based on a multicast-enabled network.
      • However, IP multicast deployment in the Internet is slow.
  • 6. Introduction
    • The use of proxy cache is an orthogonal technique for reducing
      • This technique is proved to be efficient for delivering Web objects.
      • Similar works have been proposed in which a certain portion of video file is stored in either client side and proxy server
  • 7. Introduction
    • S. Sen, J. Rexford, and D. Towsley, “Proxy prefix caching for multimedia streams,” in Proc. IEEE INFOCOM, Apr 1999.
    • J. Almedia, D. Eager, and M. Vernon, “A hybrid caching strategy for streaming media files,” in Proc. SPIE/ACM Conference on Multimedia Computing and Networking, Jan 2001
    • Y. Wang, Z.-L. Zhang, D. Du and D. Su, “A network conscious approach to end-to-end video delivery over wide area networks using proxy servers,” in Proc. IEEE INFOCOM, Apr 1998.
  • 8. Introduction
    • What are suitable proxy-assisted closed-loop transmission schedules ?
    • For a given transmission schedules, what is the optimal proxy prefix caching scheme that minimizes the transmission cost?
    • What are the resources tradeoffs (proxy cache space and transmission bandwidth etc.) for the different transmission schedules?
  • 9. Problem Setting The server-proxy path is unicast-enabled. The proxy-client path is multicast-enabled.
  • 10. Problem Setting
    • N CBR-encode video with different popularity f i
    • Video i has a video bit rate b i , and length L i seconds and size n i unit
  • 11. Design Goal
    • Ci ( vi ) is the transmission cost per unit time for video i when a prefix of length vi of video i is cached in the proxy.
    • Goal: Minimize the value of Ci ( vi ).
  • 12. Optimal Proxy Cache Allocation
    • Determine the storage vector (v1, v2 ….) that minimizes the aggregate transmission cost for a given proxy-assisted transmission scheme.
    • In this paper, it proposes two different schemes
      • Optimal 0-1 caching
      • Optimal prefix caching
  • 13. Optimal Proxy Cache Allocation
    • Optimal 0-1 caching
      • Video is either store entirely or not
      • Saving = Ci (0) – Ci ( L )
    • Optimal prefix caching
      • Only a prefix of video is stored in the proxy
      • Saving ( mi ) = Ci (0) – Ci ( mi ), where mi represents a vector of possible prefix of video i storing in the proxy.
  • 14. Optimal Proxy Cache Allocation
    • The optimal problem
    • where S is the storage size of the proxy
  • 15. Proxy-Assisted Transmission Scheme
    • The next step is how to determine Ci ( vi ) ?
    • Unicast suffix batching (SBatch)
    • Unicast patching with prefix caching (UPatch)
    • Multicast patching with prefix caching (MPatch)
    • Multicast merging with prefix caching (MMerge)
  • 16. Unicast patching with prefix caching (UPatch)
  • 17. Multicast patching with prefix caching (MPatch)
  • 18. Performance Evaluation
  • 19. Performance Evaluation
  • 20. Performance Evaluation
  • 21. Performance Evaluation
    • Optimal caching > Priority Prefix caching > Optimal 0-1 caching
    • MMerge > MPatch > UPatch > SBatch
  • 22. Conclusion
    • Under optimal proxy caching, even a small cache is sufficient to realize the transmission cost saving.
    • The selection of closed-loop transmission scheme coupled with optimal proxy caching can produce significant cost saving.