Dynamic-CBT and ChIPS

1
Dynamic-CBT and ChIPS

• Router Support for Improved Multimedia
  Performance on the Internet

Jae Chung and Mark Claypool
Computer Science Department Worcester Polytechnic
Institute Worcester, Massachusetts, USA
http//perform.wpi.edu/
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The Internet and Multimedia

• Internet routers are best effort
• No timing constraints
• Packet loss, which indicates congestion
• TCP
• Completely reliable delivery through
  retransmission
• Respond to loss as congestion
• But TCP often unsuitable for interactive
  multimedia
• Full reliability not needed
• Window-based rate fluctuations

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Multimedia Using TCP
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Multimedia Using UDP
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Multimedia on the Internet

• Multimedia often uses UDP
• Avoid delay and jitter from retransmission
• Rate-based
• Unresponsive!
• Router queue management goals
• Congestion Control
• Fairness
• Reduce Jitter

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Router Queue Management
Bursty Loss Unfairness
Drop Tail (FIFO)
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Outline

• Introduction ?
• CBT ?
• D-CBT
• ChIPS
• Conclusion

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CBT Design
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Router Queue Management
ChIPS
Drop Tail (FIFO)
Resource Reservation
Active Queue Mgmt
...
...
CBQ
RED
(Floyd, Jacobson 95)
(Floyd, Jacobson 93)
Class-Based Threshold (CBT)
(Parris, Jeffay, Smith 99)
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D-CBT Design
Responsive MM
Enable Thrsh
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Evaluation in NS

• Developed responsive multimedia application (for
  tagged UDP class)
• AIMD Media Scaling (5 discrete rates)
• MPEG-1 like transmission rates
• Implemented and validated CBT
• Implemented D-CBT and measured congestion time
  fairness
• RED vs. CBT vs. D-CBT

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Simulation (RED, CBT, D-CBT)
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Fairness RED
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Fairness CBT
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Fairness D-CBT
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Outline

• Introduction ?
• CBT and D-CBT ?
• Design ?
• Evaluation ?
• ChIPS ?
• Design
• Evaluation
• Conclusion

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Cut-In Packet Scheduling (ChIPS) Design
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ChIPS Evaluation - Jitter
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ChIPS Evaluation - Fairness
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Conclusion

• D-CBT
• Protect responsive flows from unresponsive
• Class-based consideration
• Adaptive to mix of flows
• ChIPS
• Reduce multimedia jitter during congestion

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Future Work

• Active Flow Counting (Overhead)
• For every incoming packet, update flow info
• Hash Table - O(1)
• Every ?ms, delete old flows
• Hash Table - O(n)
• Measure Overhead
• Processing Time and Memory Usage

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Future Work

• How many different classes are needed?
• Example
• 1 class is RED
• 1 class per flow is FRED
• Overhead per class
• Effects of D-CBT and ChIPS on Perceptual Quality