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PV Powerpoint

  1. 1. TCP Video Streaming to Bandwidth-Limited Access Links Puneet Mehra and Avideh Zakhor Video and Image Processing Lab University of California, Berkeley
  2. 2. Talk Outline <ul><li>Goals & Motivation </li></ul><ul><li>Our Approach </li></ul><ul><li>Experimental Results </li></ul><ul><li>Related Work </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Goal <ul><li>Efficient video streaming using TCP to bandwidth-limited receivers </li></ul><ul><li>Key Assumptions: </li></ul><ul><ul><li>Receivers have limited-bandwidth last mile connections to Internet </li></ul></ul><ul><ul><li>… and run multiple concurrent TCP networking apps </li></ul></ul><ul><li>Constraints: </li></ul><ul><ul><li>Should not modify senders or network infrastructure </li></ul></ul>
  4. 4. Motivation <ul><li>Increasingly access links are the net. Bottleneck! </li></ul><ul><ul><li>Limited Bandwidth (B/W)  Less than 1.5MBps </li></ul></ul><ul><ul><li>Users run concurrent apps  compete for limited B/W </li></ul></ul><ul><li>Most Traffic on Internet is TCP [HTTP, P2P, FTP] </li></ul><ul><ul><li>TCP handles recovery of lost packets </li></ul></ul><ul><ul><li>TCP has congestion control </li></ul></ul><ul><ul><li>UDP Streaming difficult w/ firewalls </li></ul></ul><ul><li>Problem: TCP shares bottleneck B/W according to RTT </li></ul><ul><ul><li>May Not provide enough B/W for streaming apps </li></ul></ul>
  5. 5. Example Situation High RTT Med. RTT Low RTT Congestion Most Bandwidth!
  6. 6. Talk Outline <ul><li>Motivation & Goals </li></ul><ul><li>Our Approach </li></ul><ul><li>Experimental Results </li></ul><ul><li>Related Work </li></ul><ul><li>Conclusion </li></ul>
  7. 7. Our Approach <ul><li>We developed a receiver-based bandwidth sharing system (BWSS) for TCP [INFOCOM 2003] </li></ul><ul><li>Key Idea: Break fairness among TCP flows to allow user-specified B/W allocation </li></ul><ul><li>Approach: Limit throughput of low-priority connections to provide B/W for high-priority ones </li></ul><ul><ul><li>Ensures full utilization of access link </li></ul></ul><ul><ul><li>Doesn’t require changes to TCP/senders or infrastructure </li></ul></ul>
  8. 8. BWSS Overview
  9. 9. Target Rate Allocation Subsystem <ul><li>Some apps need minimum guaranteed rate(video), others don’t (ftp) </li></ul><ul><li>User assigns each flow: </li></ul><ul><ul><li>Priority, minimum rate and weight </li></ul></ul><ul><li>Bandwidth allocation algorithm: </li></ul><ul><ul><li>Satisfy minimum rate in decreasing order of priority </li></ul></ul><ul><ul><li>Remaining B/W shared according to weight </li></ul></ul>T 1 User Prefs. σ T n
  10. 10. Flow Control System (FCS) w – TCP window RTT – Flow RTT MSS – TCP MSS
  11. 11. σ – Calculation Subsystem <ul><li>Goal: Choose σ to maximize link utilization. U = Σ i R i ( σ ) </li></ul><ul><li>Approach: Use increase/decrease in measured throughput to guide increase/decrease of σ </li></ul>R 1 R N σ = Σ i T i T 1 = R 1 σ U W 2 W 1 Link Capacity T 2 = R 2 T 1 = R 1 T 2 ≠ R 2 T 2 = R 2
  12. 12. Talk Outline <ul><li>Motivation & Goals </li></ul><ul><li>Our Approach </li></ul><ul><li>Experimental Results </li></ul><ul><li>Related Work </li></ul><ul><li>Conclusion </li></ul>
  13. 13. Experimental Setup RUDE
  14. 14. Experimental Details Invisible to Apps User Level App  easy to deploy ETH0 NIST NET Emulator BW = 960 Kbps Delay = 30 ms BWSS – Shared Library APP_1 APP_n APP_2
  15. 15. TCP vs BWSS Internet Experiments <ul><li>Video streamed at 496Kbps </li></ul><ul><li>Congestion on access link from 30s to 60s </li></ul><ul><li>Standard TCP not good enough during congestion </li></ul>TCP BWSS
  16. 16. BWSS Reduces Required Pre-Buffering <ul><li>BWSS provides 4X reduction in pre-buffering over standard TCP </li></ul>
  17. 17. SureStream TM Experimental Setup RUDE
  18. 18. RealVideo SureStream TM Internet Experiments <ul><li>Takeaway: standard TCP not good enough for streaming </li></ul>TCP TCP w/ BWSS <ul><li>Video encoded at 450Kbps, 350Kbps, 260Kbps & 64Kbps </li></ul><ul><li>Congestion on access link from 60s to 100s (320Kbps) </li></ul>Despite congestion, video streams at steady rate. Poor streaming quality
  19. 19. RealVideo SureStream TM Internet Experiments UDP TCP w/ BWSS <ul><li>Takeaway: BWSS can break fairness among flows locally, and provide additional B/W for video apps. </li></ul>UDP SureStream unable to stream at 450KBps till after congestion Constant streaming at 450Kbps
  20. 20. Related Work – TCP Streaming <ul><li>Network-Based Approaches </li></ul><ul><ul><li>Receiver-based Delay Control (RDC) [NOSSDAV 2001] </li></ul></ul><ul><ul><ul><li>receivers delay ACK packets based on router feedback </li></ul></ul></ul><ul><ul><ul><li>Mimic a CBR connection </li></ul></ul></ul><ul><li>End-Host Approaches </li></ul><ul><ul><li>Time-lined TCP (T-TCP) [ICNP 2002] </li></ul></ul><ul><ul><li>TCP Real-Time Mode (TCP-RTM) [ICNP 2002] </li></ul></ul><ul><ul><li>Must modify both sender & receiver to allow skipping “late” packets </li></ul></ul>
  21. 21. Conclusions <ul><li>BWSS allows flexible allocation of link B/W </li></ul><ul><ul><li>Breaks fairness among TCP flows “locally” in manner unavailable to TCP-Friendly UDP protocols </li></ul></ul><ul><li>BWSS enables efficient video streaming over TCP to bandwidth-limited receivers </li></ul><ul><ul><li>Better performance than standard TCP </li></ul></ul><ul><ul><li>In some cases, better performance than congestion-aware UDP </li></ul></ul><ul><li>Future Work: Incorporating UDP flows </li></ul>
  22. 22. Questions?