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TCP Video Streaming to Bandwidth-Limited Access Links

TCP Video Streaming to Bandwidth-Limited Access Links. Puneet Mehra and Avideh Zakhor Video and Image Processing Lab University of California, Berkeley. Talk Outline. Goals & Motivation Our Approach Experimental Results Related Work Conclusion. Goal.

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TCP Video Streaming to Bandwidth-Limited Access Links

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  1. Packet Video 2003 TCP Video Streaming to Bandwidth-Limited Access Links Puneet Mehra and Avideh Zakhor Video and Image Processing Lab University of California, Berkeley

  2. Packet Video 2003 Talk Outline • Goals & Motivation • Our Approach • Experimental Results • Related Work • Conclusion

  3. Packet Video 2003 Goal • Efficient video streaming using TCP to bandwidth-limited receivers • Key Assumptions: • Receivers have limited-bandwidth last mile connections to Internet • … and run multiple concurrent TCP networking apps • Constraints: • Should not modify senders or network infrastructure

  4. Packet Video 2003 Motivation • Increasingly access links are the net. Bottleneck! • Limited Bandwidth (B/W)  Less than 1.5MBps • Users run concurrent apps  compete for limited B/W • Most Traffic on Internet is TCP [HTTP, P2P, FTP] • TCP handles recovery of lost packets • TCP has congestion control • UDP Streaming difficult w/ firewalls • Problem: TCP shares bottleneck B/W according to RTT • May Not provide enough B/W for streaming apps

  5. Packet Video 2003 Example Situation Low RTT Most Bandwidth! Med. RTT High RTT Congestion

  6. Packet Video 2003 Talk Outline • Motivation & Goals • Our Approach • Experimental Results • Related Work • Conclusion

  7. Packet Video 2003 Our Approach • We developed a receiver-based bandwidth sharing system (BWSS) for TCP [INFOCOM 2003] • Key Idea: Break fairness among TCP flows to allow user-specified B/W allocation • Approach: Limit throughput of low-priority connections to provide B/W for high-priority ones • Ensures full utilization of access link • Doesn’t require changes to TCP/senders or infrastructure

  8. Packet Video 2003 BWSS Overview

  9. Packet Video 2003 σ User Prefs. Tn Target Rate Allocation Subsystem T1 • Some apps need minimum guaranteed rate(video), others don’t (ftp) • User assigns each flow: • Priority, minimum rate and weight • Bandwidth allocation algorithm: • Satisfy minimum rate in decreasing order of priority • Remaining B/W shared according to weight

  10. Packet Video 2003 w – TCP window RTT – Flow RTT MSS – TCP MSS Flow Control System (FCS)

  11. Packet Video 2003 σ – Calculation Subsystem R1 σ= Σi Ti RN • Goal: Choose σ to maximize link utilization. U = Σi Ri (σ) • Approach: Use increase/decrease in measured throughput to guide increase/decrease of σ T2≠ R2 T2 = R2 T1 = R1 T2 = R2 Link Capacity T1 = R1 U σ W1 W2

  12. Packet Video 2003 Talk Outline • Motivation & Goals • Our Approach • Experimental Results • Related Work • Conclusion

  13. Packet Video 2003 Experimental Setup RUDE

  14. Packet Video 2003 APP_1 APP_n APP_2 BWSS – Shared Library NIST NET Emulator BW = 960 Kbps Delay = 30 ms ETH0 Experimental Details User Level App  easy to deploy Invisible to Apps

  15. Packet Video 2003 TCP vs BWSS Internet Experiments • Video streamed at 496Kbps • Congestion on access link from 30s to 60s • Standard TCP not good enough during congestion BWSS TCP

  16. Packet Video 2003 BWSS Reduces Required Pre-Buffering • BWSS provides 4X reduction in pre-buffering over standard TCP

  17. Packet Video 2003 SureStreamTM Experimental Setup RUDE

  18. Packet Video 2003 RealVideo SureStreamTMInternet Experiments TCP w/ BWSS Despite congestion, video streams at steady rate. Poor streaming quality TCP • Takeaway: standard TCP not good enough for streaming • Video encoded at 450Kbps, 350Kbps, 260Kbps & 64Kbps • Congestion on access link from 60s to 100s (320Kbps)

  19. Packet Video 2003 RealVideo SureStreamTMInternet Experiments UDP TCP w/ BWSS UDP SureStream unable to stream at 450KBps till after congestion Constant streaming at 450Kbps • Takeaway: BWSS can break fairness among flows locally, and provide additional B/W for video apps.

  20. Packet Video 2003 Related Work – TCP Streaming • Network-Based Approaches • Receiver-based Delay Control (RDC) [NOSSDAV 2001] • receivers delay ACK packets based on router feedback • Mimic a CBR connection • End-Host Approaches • Time-lined TCP (T-TCP) [ICNP 2002] • TCP Real-Time Mode (TCP-RTM) [ICNP 2002] • Must modify both sender & receiver to allow skipping “late” packets

  21. Packet Video 2003 Conclusions • BWSS allows flexible allocation of link B/W • Breaks fairness among TCP flows “locally” in manner unavailable to TCP-Friendly UDP protocols • BWSS enables efficient video streaming over TCP to bandwidth-limited receivers • Better performance than standard TCP • In some cases, better performance than congestion-aware UDP • Future Work: Incorporating UDP flows

  22. Packet Video 2003 Questions?

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