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Better-Behaved Better-Performing Multimedia Networking

Better-Behaved Better-Performing Multimedia Networking. Jae Chung and Mark Claypool (Avanish Tripathi) Computer Science Department Worcester Polytechnic Institute. Outline. Motivation Approach Experimental Setup Results Conclusion Future Work. Motivation.

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Better-Behaved Better-Performing Multimedia Networking

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  1. Better-Behaved Better-Performing Multimedia Networking Jae Chung and Mark Claypool (Avanish Tripathi) Computer Science Department Worcester Polytechnic Institute

  2. Outline • Motivation • Approach • Experimental Setup • Results • Conclusion • Future Work

  3. Motivation • The Internet is predominantly designed for TCP traffic. • Best Effort ( no timing constraints) • Reliable delivery • TCP is unsuitable for Multimedia applications • …Multimedia applications use UDP

  4. Illustrative Example

  5. Approach • But, UDP is unresponsive to congestion... • Model the TCP congestion control strategy for UDP flows • Exponential decrease in data rate when congestion is encountered • Linear increase in data rate in the absence of congestion [ Jacobson et al. 1988]

  6. Issues • Multimedia Scaling • to enable the variations in the data rate • Congestion detection mechanism • when to reduce the data rate

  7. Multimedia Scaling • Directly associate transmission rates to scale values • MPEG_APP : based on MPEG-I encoding [Walpole et al. 1997]

  8. Congestion Detection • Frame loss is the indicator for congestion. • A frame is assumed lost when : • the receiver gets a frame whose sequence number is greater than the expected sequence number. • the receiver does not get any frame within a timeout interval.

  9. Operation • In case of congestion reduce scale value by half ( exponential decrease) • In the absence of congestion increase the scale value by one (linear increase)

  10. Experiments • NS - WAN Simulator developed at University of California, Berkeley

  11. Simulation 5 TCP Flows MM UDP Flow MPEG UDP Flow TCP Flow MM UDP Flow MPEG UDP Flow 5 15 25 Time ( s)

  12. Simulation Results

  13. Simulation Results

  14. Simulation Results

  15. Conclusions • “TCP-like” multimedia protocol built upon UDP • Responsive to congestion • Better Multimedia Quality • Quantitative comparison of TCP, UDP and responsive UDP • Implementation in NS

  16. Future Work • Content based multimedia scaling • Experiments with other media formats • Evaluation of perceptual quality by user studies • Quantitative analysis of data loss ( ratio of packets sent and packets lost) • “TCP Friendly” Evaluation

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