1. INFOCOM 2003 1 A Receiver-Driven Bandwidth Sharing System (BWSS) for TCP Puneet Mehra, Avideh Zakhor UC Berkeley, USA Christophe De Vleeschouwer Université Catholique de Louvain, Belgium

2. INFOCOM 2003 2 Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

3. INFOCOM 2003 3 Motivation Most traffic on Internet is TCP HTTP, FTP, P2P,… In many cases access links are bottleneck Limited Bandwidth (B/W) eg: DSL/Cable < 1.5Mbps User run many apps that compete for B/W Problem: TCP shares bottleneck B/W according to RTT Not fair to flows w/ large RTT Doesn’t consider application needs or user prefs!

4. INFOCOM 2003 4 Example Situation High RTT Med. RTT Low RTT Congestion

5. INFOCOM 2003 5 Goal & Approach Goal: Let user control application B/W allocations User preferences dictate bandwidth allocation Approach: limit throughput of low-priority flows to provide additional B/W for high-priority ones Ensure full utilization of access link Don’t change TCP/senders or routers  easily deployable!

6. INFOCOM 2003 6 Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

7. INFOCOM 2003 7 BWSS Overview

8. INFOCOM 2003 8 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

9. INFOCOM 2003 9 BWSS Overview

10. INFOCOM 2003 10 Flow Control System (FCS) w – TCP window d – delay in ACKs RTT – Flow RTT MSS – TCP MSS

11. INFOCOM 2003 11 BWSS Overview

12. INFOCOM 2003 12 σ – Calculation Subsystem Goal: Choose σ to maximize link utilization. U = Σ i R i (σ) Approach: Iteratively increase/decrease σ and measure the impact on utilization R1R1 RNRN σ 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

13. INFOCOM 2003 13 BWSS Overview

14. INFOCOM 2003 14 Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

15. INFOCOM 2003 15 Example of User Preferences Time 0: Min. Rate = 0 Kb/s weights = 1,2,3 for S0-S2 Priority -> S0 (max), S2(min) Time 300: Min Rate = 600 Kb/s TCP BWSS

16. INFOCOM 2003 16 Network-Congestion Example Priorities: increasing from S0-S2 Min Rate: S0,S2 – 600Kb/s S1 – 100 Kb/s Time 400s to 1200s 700Kb/s Interfering TCP traffic S2 limited to 300Kb/s

17. INFOCOM 2003 17 Multimedia Streaming Example S0 – Ftp traffic. Low Priority Min Rate = 700Kb/s S1 – Streaming at 450Kb/s High Priority 300Kb/s UDP flow (400s-1000s)

18. INFOCOM 2003 18 Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

19. INFOCOM 2003 19 BWSS Implementation ETH0 BWSS User-space shared library setsockopt() No Kernel Mods! APP_1APP_nAPP_2 Invisible to Apps

20. INFOCOM 2003 20 Experimental Setup Host PC running Linux 2.4.8 kernel AT&T Cable modem connection

21. INFOCOM 2003 21 Experiment 1 – User Preferences BWSS allows flexible allocation of B/W Standard TCP Weighted Fair Sharing Ratios: 3,2,1 Minimum Rate of 100Kb/s Priorities: Blue, green, red

22. INFOCOM 2003 22 Related Work Network-Modifying Solutions Router Scheduling Policies WFQ, W2FQ: allow B/W allocation Require infrastructure changes  little deployment Network Appliances – PacketShaper Placed at network ingress  does traffic management Not easy to manage individual preferences End-Host solution Modify receiver’s window [Spring et al, 2000] Prioritize short-lived flows over longer ones Focus: reduce queuing delay for interactive apps (telnet)

23. INFOCOM 2003 23 Conclusions BWSS allows user to allocate link B/W Flexible B/W allocation model Adapts to changing network conditions No changes to TCP/senders/routers Implemented as shared library  easily deployable Enables efficient video streaming over TCP Simulations show better performance than standard TCP Additional Internet experiments validate [TCP Based Video Streaming using Receiver-Driven Bandwidth Sharing, Packet Video 2003, To appear]