1. 1 PV'2003, Nantes France, April 2003 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/

2. PV'2003, Nantes France, April 20032 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

3. PV'2003, Nantes France, April 20033 The Wolf on the Prowl – Transport Protocols for Video Streaming video doesn’t 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?)

4. PV'2003, Nantes France, April 20034 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

5. PV'2003, Nantes France, April 20035 Outline Introduction  Background  Experiments Analysis Conclusions

6. PV'2003, Nantes France, April 20036 RealVideo Network Characteristics SureStream (is it effective?) –Allows bandwidth scaling Buffer (how fast is it filled?) –Smoother playout Server RTSP Data: TCP or UDP -Choice automatic -We force

7. PV'2003, Nantes France, April 20037 Outline Introduction  Background  Experiments  Analysis Conclusions

8. PV'2003, Nantes France, April 20038 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 Internet Client Hub Router 10Mbps DSL 700Kbps Client Token Bucket Filter UDP TCP Server

9. PV'2003, Nantes France, April 20039 Outline Introduction  Background  Experiments  Analysis –Bandwidth  –TCP-Friendly –Media Scaling –Buffering Rate Conclusions

10. Head-to-Head Bandwidth

11. PV'2003, Nantes France, April 200311 A Sheep in Wolf’s Clothing? Remove low bandwidth (36%) Then remove unscalable (14%) [PFTK98]

12. Media Scaling Distribution

13. Media Scaling Dynamics

14. Media Scaling Adaptation Speed

15. Buffering Rate to Playout Rate

16. PV'2003, Nantes France, April 200316 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

17. PV'2003, Nantes France, April 200317 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

18. 18 PV'2003, Nantes France, April 2003 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/