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Improvements in Core-Stateless Fair Queueing (CSFQ)

Improvements in Core-Stateless Fair Queueing (CSFQ). Ling Huang U.C. Berkeley cml.me.berkeley.edu/~hlion. Achievements. Analyze the limitation of current approach Failure to work with congestion avoidance algorithm. H eavy depen d ence on the estimation algorithms

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Improvements in Core-Stateless Fair Queueing (CSFQ)

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  1. Improvements in Core-Stateless Fair Queueing (CSFQ) Ling Huang U.C. Berkeley cml.me.berkeley.edu/~hlion

  2. Achievements • Analyze the limitation of current approach • Failure to work with congestion avoidance algorithm. • Heavy dependence on the estimation algorithms • Estimation has big deviation when many flows startup simultaneously and during bursty traffic. • Achieve three improvements • Achieving fair share when working with congestion avoidance algorithm. • Application of high order Low-Pass-Filter (LPF) in flow arrival rate estimation. • Application of control-theory in fair share estimation.

  3. Algorithm of CSFQ • Edge routers put flow state in packet‘s header. • Core routers estimate fair share and drop. incoming packets with probability of • A flow should get bandwidth. • Core router updates fair share  as follows: if (A > C) new = old * C / F else new = max (ri), where ri active flows Combining fair share computation and probabilistic dropping to approximate fair queueing!

  4. Improv.1: CSFQ working with TCP Vegas • CSFQ get fare share to incoming flows, but • Not accurately approximate delay properties of Fair Queueing. • Incompatible with congestion avoidance mechanisms. Fig 1. CSFQ work with TCP Reno Fig 2. CSFQ work with TCP Vegas

  5. Improv. 1: CSFQ working with TCP Vegas • High priority queue in core router • Flows whose rates are less than their fare share go into high priority queue and get service first. • Restores fairness when work with TCP Vegas. Fig 3. CSFQ + Priority Queue Fig 4. CSFQ + Priority Queue work with TCP Reno work with TCP Vegas

  6. Improv. 2: LPF in arrival rate estimation • Current Approach employ 1st order Low-Pass-Filter: • Better properties from 2nd order Low-Pass-Filter: • Fast response to burst traffic. • Estimation result more smooth.

  7. Improv. 2: LPF in arrival rate estimation • Fast response to burst traffic Input singal Output of 1st order LPF Output of 2nd order LPF Followings are the same Fig 5. Response to pulse signal

  8. Improv. 2: LPF in arrival rate estimation • Rate estimation for arrival traffic Fig 6. Estimation of arrival rate for UDP(1Mbps) Fig 7. Estimation of arrival rate for TCP (0.5Mbps)

  9. Improv. 2: LPF in arrival rate estimation • Results of 2nd Low-Pass-Filter in CSFQ • Service allocated to flows more fare. Fig 8. CSFQ + Priority Queue + 2nd LPF Fig 9. CSFQ + Priority Queue + 2nd LPF work with TCP Reno work with TCP Vegas

  10. R Q Q0 Cs Improv. 3: Applying control theory in CSFQ Flow 1 Flow n • Picture: Traffic model • faucet and Exponential Average Exponential Average Arrival Rate Arrival Rate Packet Dropper R Estimating accepting rate Q0 Cs Q Observer Fig 10. Architecture of CSFQ scheduling: the same model as that in a water reservation system

  11. R Q Q0 Cs Improv. 3: Applying control theory in CSFQ • Dynamic equation: using queue occupancy information to compute arrival rate. R: the aggregate accepted traffic during one update interval. Cs: the output link capacity. Q: the buffer occupancy at current time. Q0:equilibrium point that we want the buffer occupancy to be.

  12. Improv. 3: Applying control theory in CSFQ • Use queue occupancy information to predict the next allowed accepting rate: flow and congestion control. • Allocate the allowed accepting rate to the incoming flows, fair share is the unique solution of equation:

  13. Improv. 3: Applying control theory in CSFQ • Results Fig 11. CSFQ + control theory Fig 12. CSFQ + control theory work with TCP work with TCP Reno

  14. Improv. 3: Applying control theory in CSFQ • Results (cont.) Fig 13. CSFQ + control theory work with TCP Vega Possible reason: priority queue confusing control system with buffer length. Fig 14. Average throughput by a TCP sharing a link of capacity 10 Mbps with (n-1) UDP flows. ( Import from [Hoon-Tong’00] )

  15. Improv. 3: Applying control theory in CSFQ • Conclusion: control theory produce stable and robust system. • Without the the estimation of aggregate arrival rate and accepted traffic. • Compute fare share continuously. • Exhibit good transient and steady behavior. • Achieve high utilization.

  16. Summary • Three improvements in CSFQ • High priority helps CSFQ achieve fair share when working with congestion avoidance algorithm. • High order Low-Pass-Filter (LPF) helps improve fair share rate. • Control-theory produce robust and highly utilized system. • CS268 is a productive class • Paper review and lecture let me know every aspect of network. • Class project help me go deep into algorithm of resource allocation and packet scheduling. • Work hard, you get achievement!

  17. CSFQ work with TCP RenogCSFQ + Priority Queue work with TCP Reno CSFQ + Priority Queue + 2nd LPF CSFQ + control theory work with TCP Reno work with TCP Reno

  18. CSFQ work with TCP VegasCSFQ + Priority Queue work with TCP Vegas CSFQ + Priority Queue + 2nd LPF CSFQ + control theory work with TCP Vegas work with TCP Vegas

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