Measurements of the Congestion Responsiveness of Windows Streaming Media

1. Measurements of the Congestion Responsiveness of Windows Streaming Media James Nichols, Mark Claypool, Robert Kinicki and Mingzhe Li Computer Science Department Worcester Polytechnic Institute Massachusetts, USA NOSSDAV 2004 - Kinsale, County Cork, Ireland

2. Network Impact of Streaming Media • Streaming Media has specific bitrate and timing requirements. • Flows unresponsive to congestion can cause unfairness and contribute to congestion collapse. • Streaming Media applications rely on the application layer to provide adaptability to available capacity • Windows Streaming Media (WSM) uses Intelligent Streaming NOSSDAV 2004

3. Methodology • Construct testbed • Create/adapt tools • Encode content • Systematic control • Examine SBR clip • Range of SBR clips • MBR clips • Vary loss and latency NOSSDAV 2004

4. Single Bitrate Clip Experiment • Hypothesis: SBR clips are unresponsive to congestion • Latency: 45 ms • Induced loss: 0% • Bottleneck capacity: 725 Kbps • Start a TCP flow through the link • 10 Seconds later stream a WSM clip • Measure achieved bitrates and loss rates for each flow NOSSDAV 2004

5. 340 Kbps Clip - Bottleneck Capacity 725 Kbps TCP- Friendly? < 0.001 packet loss After 15 seconds

6. 548 Kbps Clip - Bottleneck Capacity 725 Kbps Not TCP- Friendly! ~ 0.003 packet loss for WSM ~ 0.006 packet loss for TCP after 15 seconds

7. 1128 Kbps Clip - Bottleneck Capacity 725 Kbps Responsive To Capacity?

8. SBR Clips - Bottleneck Capacity 725 KbpsBuffering Period NOSSDAV 2004

9. SBR Clips - Bottleneck Capacity 725 KbpsPlayout Period NOSSDAV 2004

10. Multiple Bitrate Clips • Hypothesis: Multiple Bitrates make WSM more responsive to congestion • Same experiment as before, but with different encoded content • Vary network capacity: 250, 725, 1500 Kbps • Created two sets of 10 multiple bitrate clips • Experiments with lots of other MBR clips NOSSDAV 2004

11. Multiple Bitrate Content • First set of clips (adding lower): • 1128 Kbps • 1128-764 Kbps • 1128-764-548 Kbps • … • 1128-764-548-340-282-148-109-58-43-28 Kbps NOSSDAV 2004

12. Multiple Bitrate Clips Buffering Playout NOSSDAV 2004

13. Additional experiments • Not enough time to discuss all the results • Different bottleneck capacities • Vary loss rate and latencies • Also looked at other network level metrics: interarrival times, and burst lengths. NOSSDAV 2004

14. Conclusions • WSM is not CBR • Buffering period • Not TCP-friendly • Responds to capacity • Chooses highest rate less than capacity • Otherwise, lowest rate available • Performance depends upon encoding NOSSDAV 2004

15. Future Work • Run the same experiments with other streaming technologies: RealVideo and Quicktime • Examine the effects of different content types • Build NS simulation model of streaming media for use in future research NOSSDAV 2004

16. Measurements of the Congestion Responsiveness of Windows Streaming Media James Nichols, Mark Claypool, Robert Kinicki and Mingzhe Li http://perform.wpi.edu NOSSDAV 2004 - Kinsale, County Cork, Ireland