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


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

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