1. Scalable On-Demand Media Streaming with Packet Loss Recovery A. Mahanti, D. L. Eager, (USask) M. K. Vernon, D S-Stukel (Wisc) Presented by Cheng Huang 04.08.2004

2. 2 Introduction VOD is cool, but might also be expensive  Naïve implementation: connection per user  Fortunately, users favor a few “hot” movies.  It is possible to have inexpensive approach to effectively share resources (server, network, etc.) and serve lots of requests. Target of the on-demand streaming scheme  Scalable and reliable  Fundamental trade-offs Server bandwidth (network bandwidth), startup delay and client bandwidth Client buffer requirement (might be of less concern)

3. 3 Outline Periodic Broadcast Schemes Bandwidth Skimming Scheme Conclusion

4. 4 Outline Periodic Broadcast Schemes Bandwidth Skimming Scheme Conclusion

5. 5 Pyramid Broadcast S. Viswanathan, T. Imielinski 1996

6. 6 Skyscraper Broadcast K. A. Hua, S. Shen 1997

7. 7 Fibonacci Broadcast

8. 8 Optimized Periodic Broadcast A. Mahanti, D. L. Eager, M. K. Vernon, D. S.-Stukel 2001

9. 9 Optimized Periodic Broadcast (cont.) General segment length

10. 10 Generalized OPB Given the client reception bandwidth as constraint  b: maximum client reception bandwidth  r: bandwidth of each stream  s: number of streams client listen to concurrently b = r*s

11. 11 Performance of OPB

12. 12 Optimized Periodic Broadcast

13. 13 Optimized Periodic Broadcast

14. 14 Loss Recovery Strategy Digital Fountain approach  Use Error Correction Codes to generate n symbols from k original symbols (n >> k) Symbol: frame, packet, etc.  Recover the k original symbols from any k out of n coded symbols

15. 15 Generalized RPB Reliable Periodic Broadcast (RPB)  Maximum tolerable loss rate p need L/(1-p) packets in order to receive L packets  Segment length (a = 1/(1-p))

16. 16 Performance of RPB

17. 17 Outline Periodic Broadcast Schemes Bandwidth Skimming Scheme Conclusion

18. 18 Bandwidth Skimming Scheme

19. 19 Bandwidth Skimming Scheme (cont.)

20. 20 Reliable Bandwidth Skimming Pros  Bandwidth decreases as the client request rate decreases  VCR functionality – fast forward Protocol  Primary stream is transmitted at rate 1  Secondary stream is transmitted at rate p/(1-p)  Merging happens between primary streams, as well as secondary streams Real system in Univ. of Wisconsin

21. 21 Reliable Bandwidth Skimming (cont.)

22. 22 Conclusions Propose two reliable on-demand streaming schemes  RPB  RBS Schemes investigate the fundamental trade- offs of on-demand streaming service