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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

Improvements in Core-Stateless Fair Queueing (CSFQ)

Ling Huang

U.C. Berkeley

cml.me.berkeley.edu/~hlion


Achievements
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.


Algorithm of csfq
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!


Improv 1 csfq working with tcp vegas
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


Improv 1 csfq working with tcp vegas1
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


Improv 2 lpf in arrival rate estimation
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.


Improv 2 lpf in arrival rate estimation1
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


Improv 2 lpf in arrival rate estimation2
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)


Improv 2 lpf in arrival rate estimation3
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


Improv 3 applying control theory in csfq

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


Improv 3 applying control theory in csfq1

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.


Improv 3 applying control theory in csfq2
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:


Improv 3 applying control theory in csfq3
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


Improv 3 applying control theory in csfq4
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] )


Improv 3 applying control theory in csfq5
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.


Summary
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!


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


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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