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Internet Streaming Media Delivery:

Delving into. Internet Streaming Media Delivery:. A quality and Resource Utilization Perspective. Zhen Xiao Joint work with Lei Guo, Enhua Tan, Songqing Chen, Oliver Spatchcheck, and Xiaodong Zhang. ACM SIGCOMM Internet Measurement Conference (IMC'06), October 2006.

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Internet Streaming Media Delivery:

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  1. Delving into Internet Streaming Media Delivery: A quality and Resource Utilization Perspective Zhen Xiao Joint work with Lei Guo, Enhua Tan, Songqing Chen, Oliver Spatchcheck, and Xiaodong Zhang ACM SIGCOMM Internet Measurement Conference (IMC'06), October 2006

  2. Multimedia on the Internet • Education and research • News media • Entertainment and gaming • Advertisement

  3. Streaming Media Streaming server CDN/MDN

  4. Pseudo Streaming Web server http://www.YouTube.com/ http://video.google.com/ meta file HTTP

  5. Streaming Media • Thousands of concurrent streams • Flexible response to network congestion • Efficient bandwidth utilization • High quality to end users • Challenges and techniques

  6. Existing Measurements • Access pattern and user behaviors • A bunch of measurement studies • Server clusters, media proxies • Streaming mechanism and delivery quality • Few studies • Traffic volume … • Downloading > pseudo streaming > streaming (WWW’05, cookie talk 2005) • P2P >> all other media delivery systems

  7. Our Measurement • Investigate modern streaming services • The delivery quality and resource utilization • Collect a large streaming media workload • From thousands of home users and business users • Hosted by a large ISP • Packet level instead of server logs • Analyze commonly used streaming techniques • Automatic protocol switch • Fast Streaming • MBR encoding and rate adaptation

  8. Outline • Traffic overview • Protocol rollover • Fast Streaming • Rate adaptation • Conclusion

  9. Traffic Overview • User communities • Home user • Business user • Media hosting services • Self-hosting • Third-party hosting

  10. Number of requests Business users access more audio than home users

  11. On-demand media: File length Audio Video Business users tend to access longer audio/video files music previews pop songs

  12. On-demand media: Playback duration Audio Video Business users tend to play audio/video longer pop songs music previews

  13. Live media: Playback duration Audio Video Business users tend to access live audio/video longer

  14. Traffic Overview • User communities • Home user • Business user • Working environment affects access pattern • Media hosting services • Self-hosting • Third-party hosting News and entertainment sites

  15. Traffic Overview • User communities • Business users tend to access streaming media longer than home users • Working environment affects access pattern • Media hosting services • Self-hosting • Third-party hosting

  16. Media hosting services

  17. Outline • Traffic overview • Protocol rollover • Fast Streaming • Rate adaptation • Conclusion

  18. Protocol Rollover Streaming server Media player RTSP/UDP RTSP/TCP Embed RTSP commands in HTTP packets HTTP/TCP Traffic volume: UDP: 23% TCP: 77% HTTP: rare

  19. Protocol rollover time Startup latency = protocol rollover time + transport setup time + startup buffering time Windows media service RealNetworks media service Protocol rollover increases user startup time significantly

  20. Protocol selection and rollover avoidance • Most streaming traffic are TCP-based • The usage of NAT? • MMS clients report private IP address in clear text • Home user: 98.3% report 192.168.*.* • Business user: 89.5% report 192.168.*.* • Protocol rollover sessions are minor • Home user: 7.37% • Business user: 7.95% • Most streaming sessions use TCP directly • Why?

  21. Protocol selection and rollover avoidance • Windows media service • Specify the protocol in the media meta file Use URL modifiers to avoid protocol rollover Ex: rtspt://xxx.xxx.com:/xxx.wmv • More than 70% • RealNetworks media service • NAT transversal techniques

  22. Outline • Traffic overview • Protocol rollover • Fast Streaming • Rate adaptation • Conclusion

  23. Fast Streaming • Fast Streaming: deliver media data “faster” than its encoding rate • Fast start • Fast cache • Fast recovery • Fast reconnect • Always TCP-based

  24. Media objects delivered with Fast Cache(VoD home user workload) File length Encoding rate Fast Cache is more widely used for media files with longer length and higher encoding rate.

  25. Bandwidth Utilization PLAY RTSP/1.0 Bandwidth: 1.12 Mbps Speed: 20.5 RTSP /1.0 200 OK Speed: 5 Fast Cache Normal TCP

  26. Fast Cache smooth bandwidth fluctuation Rebuffer ratio = rebuffer time / play time Fast Cache Normal TCP

  27. Fast Cache produces extra traffic Most streaming sessions only request the initial part of a media object Fast Cache: 55% Normal TCP: 5% Over supplied data

  28. Server response time DESCRIBE foo.wmv RTSP/1.0 SRT RTT sniffer RTSP /1.0 200 OK SDP Third party media service Self-hosting media service

  29. Server Load Win XP Windows Server 2003 Windows media load simulator Ethernet … Server log Some CDNs/MDNs do not support Fast Cache at all 1 X 4 X

  30. Outline • Traffic overview • Protocol rollover • Fast Streaming • Rate adaptation • Conclusion

  31. Rate Adaptation Multiple-bit-rate encoding 96Kbps 128Kbps 320Kbps … 1.128Mbps Stream switch WM: Intelligent streaming RM: SureStream Stream thinning: deliver key frame only Video cancellation

  32. MBR encoding on-demand audio audio stream in video objects live audio video stream in video objects 42% on-demand video are MBR encoded

  33. Stream switch Play-out buffer Streaming switch latency Low quality duration 40% 30 sec 60% 3 sec Stream switch is often not smooth

  34. Stream thinning 30 sec 70%

  35. Fast Cache and stream switch Do not work with each other: fewer stream switches than MBR encoded objects When network congestion occurs … fill play-out buffer playing buffering playing buffering playing buffering time 5 sec Like pseudo streaming When rebuffer occurs

  36. Streaming quality and playback duration Home user business user >100 sec 88% Longer duration sessions have higher prob. of quality degradation Business user workload has more quality degradation

  37. Streaming quality summary The quality of media streaming on the Internet leaves much to be improved

  38. Coordinating caching and rate adaptation • Fast Cache: aggressively buffer data in advance • Over-utilize CPU and bandwidth resources • Neither performance effective nor cost-efficient • Rate adaptation: conservatively switch to lower bit rate stream • Switch handoff latency • Coordinated Streaming Lower bound Prevent switch latency Upper bound Prevent aggressive buffering

  39. Coordinated Streaming Rebuffering ratio Over-supplied data Switch latency

  40. Conclusion • Quality of Internet streaming • Often unsatisfactory • Need to improve • Modern streaming media services • Over-utilize CPU and bandwidth resources • Not a desirable way to improve quality • Coordinated Streaming • Combine merits of both caching and rate adaptation • Simple but effective

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