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TCP-Carson A Loss-event Based Adaptive AIMD Protocol for Long-lived Flows

TCP-Carson A Loss-event Based Adaptive AIMD Protocol for Long-lived Flows. Hariharan Kannan Advisor: Prof. M Claypool Co-Advisor: Prof. R Kinicki Reader: Prof. D Finkel. Outline. Introduction TCP Behavior TCP-Carson Evaluation Summary Future Work. Introduction. Modern Internet

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TCP-Carson A Loss-event Based Adaptive AIMD Protocol for Long-lived Flows

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  1. TCP-CarsonA Loss-event Based Adaptive AIMD Protocol for Long-lived Flows Hariharan Kannan Advisor: Prof. M Claypool Co-Advisor: Prof. R Kinicki Reader: Prof. D Finkel

  2. Outline • Introduction • TCP Behavior • TCP-Carson • Evaluation • Summary • Future Work

  3. Introduction • Modern Internet • Short-lived flows e.g. HTTP • Streaming media e.g. Real audio • Real-time applications e.g. VoIP services • Long-lived flows e.g. FTP • Heavy tailed • 80% bytes are from few connections [Matta, ‘01] • Use TCP • 80% of traffic is TCP [Hidenari, ‘97] • Responsive to congestion – Internet stability • No loss • Router Support to TCP like behavior • More applications are built on top of TCP • Optimize long-lived flow performance in TCP like fashion Long-lived

  4. Modifications to TCP • TCP – Two phases • Slow Start: (till first loss of packet) • Aim: Rough estimate of available bandwidth. • Congestion Manager [Bala, ’99], TCP Fast Start [Venkat, ‘98] • Congestion Avoidance: • Aim: Optimize window-size, react to network congestion • Reno, New-Reno, Vegas, Tahoe • AIMD [Yang, ‘00]: window size = f (increase “a”, decrease “1-b”) • Conventional TCP (1, 0.5) • Other Equations: a=3b/(2-b) , a=4(1-b²)/3 • TCP-Carson * • TCP variant, built on top of RENO • Window-based • Fully reliable • Responsive to Congestion * Carson City: Located in the State of Nevada, Population: 52457, Founded 1858 For more details visit http://www.carson-city.nv.us/

  5. drops The Probing Problem

  6. TCP-Carson • Detects Steady State • Losses are periodic • Loss interval: Interval in packets between two successive losses • Adapt responsiveness (reaction) • Adapt “a”, “b”: (increase, decrease) • Benefits: Increase throughput, reduce loss, reduce window-size variance

  7. Outline • Introduction • TCP Behavior • Congestion Window • Loss interval • TCP-Carson • Evaluation • Summary

  8. Topology s1 r1 1 Mb, 40ms R1 R2 s2 r2 2 Mb, 10ms 2 Mb, 10ms Drop tail Q = 15 Drop tail Q = 15 r3 s3

  9. 1 16 1 Unsteady Steady Steady - b/w RTX-TO + b/w TCP – Cwnd Behavior

  10. 1 16 1 Steady Unsteady Steady TCP – Loss interval • Loss Interval : Number of packets between successive loss events

  11. Outline • Introduction • TCP Behavior • TCP-Carson • Steady State Detection • Metrics • Mechanism • Algorithm • Evaluation • Summary

  12. Steady State Detection - Metrics 1 1 16

  13. Steady State Detection - Metrics 1 16 1

  14. Steady State Detection - Algorithm • Metric : Weighted Average Loss Interval • Used in TFRC [Floyd, ‘01] • Evaluated overlapping and distinct windows • Evaluated window sizes from 4 – 32 • Chose sliding-32 • Equal weights to recent 16 • Exponentially decreasing weights for prior 16 • wti = 1, 1 ≤ i ≤ 16 = 1 - [(i – n/2)/(n/2 +1)] , 17 ≤ i ≤ 32

  15. Steady State Detection - Algorithm • When Steady? • wali(i+1) = wali(i) ± [ 0.1 * wali(i)] • When Unsteady? • wali(i+1) != wali(i) ± [ 0.1 * wali(i)] • Retransmission timeout • No loss for long time • See how it works!!!

  16. Steady State – 10 Flows

  17. 4 8 16 8 4 Steady State – Varying # of flows 4 8 16 8 4

  18. TCP–Carson : Algorithm • AIMD Table: • detect_state(loss_interval) • if (steady) { go_up() } • if (unsteady) {go_down()} //become TCP • Okay dude!!! Show me the results!!!! TCP (start here)

  19. Evaluation • 1 TCP-Carson • 1 TCP-Carson, 1 CBR • 1 TCP-Carson, 1 TCP-Reno • 4 TCP-Carson, 4 TCP-Reno • 7 TCP-Carson, 1 TCP-Reno • 1 TCP-Carson, 7 TCP-Reno • 8 TCP-Carson • 20 TCP-Carson • Varying flow life-times – Varying number of flows

  20. 1TCP-Carson

  21. 1 TCP-Carson, 1 CBR(0.5Mb) 1 Carson, 1 UDP 1 Carson, 1 UDP 1 Carson

  22. 1TCP-Carson, 1TCP-Reno

  23. 4-Carson, 4-Reno

  24. 8 TCP-Carson flows

  25. Evaluation Single Flow 1-Carson, 1-Reno 4-Carson, 4-Reno 8-Carson / 8-Reno * Note: Bottleneck bandwidth was 1.5M • TCP friendly in all cases • Average throughput less than TCP response function for (loss, RTT) combination

  26. Summary • TCP variant (on top of Reno) • Detects Steady State • Adapts responsiveness • Benefits: • Increase throughput • Reduces loss • Reduce window-size variance • End-to-End protocol

  27. Future Work • AIMD action • RED/ECN effect • Application performance • Slow-start, high congestion periods • Steady state detection algorithms

  28. TCP-CarsonA Loss-event Based Adaptive AIMD Protocol for Long-lived Flows Hariharan Kannan Advisor: Prof. M Claypool Co-Advisor: Prof. R Kinicki Reader: Prof. D Finkel

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