Measurement%20of%20the%20Congestion%20Responsiveness%20of%20RealPlayer%20Streaming%20Video%20Over%20UDP

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Measurement of the Congestion Responsiveness of
RealPlayer Streaming Video Over UDP

• Jae Chung, Mark Claypool, Yali Zhu
• Computer Science Department
• Worcester Polytechnic Institute
• Worcester, MA, USA
• http//www.cs.wpi.edu/claypool/papers/h2h/

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The Hungry Wolf Bandwidth Requirements for
Video

• Voice uses 32-64 Kbps, but video has broader
  range of data rates
• Videoconference 0.1 Mbps (H.261, MPEG-4)
• VCR 1.2 Mbps (MPEG-1)
• Broadcast quality 2-4 Mbps (MPEG-2)
• HDTV quality 25-34 Mbps (MPEG-2)
• ? Thus, potential for more than network capacity

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The Wolf on the Prowl Transport Protocols for
Video

• Streaming video doesnt always like TCP
• Wants rate-based not window-based
• Can tolerate some loss
• AIMD causes rate fluctuations
• ?So, uses UDP where application controls
• But UDP has no built-in congestion control
• Unfair, unfriendly, and even collapse!
• Approaches to have router detect and limit
• Often model video as CBR firehose (is it?)

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The Wolf Pack Commercial Video

• Commercial products have major impact

• Have been studies characterizing commercial
  traffic
• Bandwidth use, frame rate, user use
• But no work measuring responsiveness, or lack of
  it, of commercial video products
• ?Measure responsiveness of RealPlayer over UDP

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Outline

• Introduction ?
• Background ?
• Experiments
• Analysis
• Conclusions

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RealVideo Network Characteristics

• SureStream (is it effective?)
• Allows bandwidth scaling
• Buffer (how fast is it filled?)
• Smoother playout

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Outline

• Introduction ?
• Background ?
• Experiments ?
• Analysis
• Conclusions

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Responsiveness Measurement Environment

• Encoding rates RealTracker
• Data rates via tcpdump
• Loss rates and round-trip times via ping
• TBF to limit bandwidth
• 75, 150, 300, 600 kbps
• 79 (of 100) Clips, 2 measurements per clip

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Outline

• Introduction ?
• Background ?
• Experiments ?
• Analysis
• Bandwidth ?
• TCP-Friendly
• Media Scaling
• Buffering Rate
• Conclusions

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Head-to-Head Bandwidth
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A Sheep in Wolfs Clothing?
PFTK98

• Remove low bandwidth (36)
• Then remove unscalable (14)

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Media Scaling Distribution
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Media Scaling Dynamics
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Media Scaling Adaptation Speed
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Buffering Rate to Playout Rate
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Summary

• No concrete incentives to respond to congestion
• In fact, may be rewarded for not
• However, RealVideo clearly adjusts
• Often TCP-Friendly
• Content providers need to provide chance for
  scalability
• Scaling levels
• Buffering at higher rate is bad for network since
  bursty
• Why not TCP? ? API is limiting

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Future Work

• Other commercial Players
• Microsoft Media Player
• Perceptual quality of video over TCP versus UDP
• Characterization of clips on Internet
• So can examine typical clips

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Measurement of the Congestion Responsiveness of
RealPlayer Streaming Video Over UDP

• Jae Chung, Mark Claypool, Yali Zhu
• Computer Science Department
• Worcester Polytechnic Institute
• Worcester, MA, USA
• http//www.cs.wpi.edu/claypool/papers/h2h/