1. Packet Video 2003 1 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 2 Talk Outline Goals & Motivation Our Approach Experimental Results Related Work Conclusion

3. Packet Video 2003 3 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 4 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 5 Example Situation High RTT Med. RTT Low RTT Congestion Most Bandwidth!

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

7. Packet Video 2003 7 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 8 BWSS Overview

9. Packet Video 2003 9 Target Rate Allocation Subsystem 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 T1T1 User Prefs. σ TnTn

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

11. Packet Video 2003 11 σ – Calculation Subsystem Goal: Choose σ to maximize link utilization. U = Σ i R i (σ) Approach: Use increase/decrease in measured throughput to guide increase/decrease of σ R1R1 RNRN σ = Σ i T i T 1 = R 1 σ U W2W2 W1W1 Link Capacity T 2 = R 2 T 1 = R 1 T 2 ≠ R 2 T 2 = R 2

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

13. Packet Video 2003 13 Experimental Setup RUDE

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

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

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

17. Packet Video 2003 17 SureStream TM Experimental Setup RUDE

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

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

20. Packet Video 2003 20 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 21 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 22 Questions?