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Analysis of Active Queue Management Jae Chung and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA.

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Presentation on theme: "Analysis of Active Queue Management Jae Chung and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA."— Presentation transcript:

1 Analysis of Active Queue Management Jae Chung and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA http://perform.wpi.edu/

2 NCA 2003 WPI Analysis of AQM #2 Active Queue Management Queue Sink Outbound LinkRouterInbound Link Sink TCP ACK… Queue Sink Outbound LinkRouterInbound Link Sink TCP ACK… Queue Sink Outbound LinkRouterInbound Link Sink TCP ACK… Drop!!! Queue Sink Outbound LinkRouterInbound Link Sink TCP Queue Sink Outbound LinkRouterInbound Link Sink TCP AQM Congestion Congestion Notification… ACK… Queue Sink Outbound LinkRouterInbound Link Sink TCP AQM Advantages Reduce packet losses (due to queue overflow) Reduce queuing delay

3 NCA 2003 WPI Analysis of AQM #3 Related Work: Analysis of AQM Control Theory Approach (Hollot, Infocom 01) –Model TCP and AQM Behaviors (Laplace domain). –Apply Classical Control Theory (through analysis). –Params not obvious for understanding control info. Queue Law (Firoiu, Infocom 00) –Model Average TCP Throughput and the behavior of Average Queue Length at congested router. –Shows the impact of traffic parameters on AQM. –Not suitable for system stability analysis. –Good for analyzing and configuring AQMs using average queue.

4 NCA 2003 WPI Analysis of AQM #4 Contribution Extend Firoiu’s to a General Queue Law –Simplify the queue law to better illustrate the effect of traffic parameters on AQM. –Extend the queue law to support Explicit Congestion Notification (ECN) and study the impact of ECN on AQM congestion control. Analysis of RED-Family AQM –Evaluate RED-Family AQMs (RED, Gentle RED and Adaptive RED) –Demonstrate ECN gains on packet loss rates.

5 NCA 2003 WPI Analysis of AQM #5 Outline Introduction Queue Law Impact of ECN RED Family AQM Analysis of REDs Summary

6 NCA 2003 WPI Analysis of AQM #6 Average TCP Window (Bulk Transfers) Function of congestion notification p robability (CNP) only. Not affected by the number of flows (N), RTT or Service Rate (SR). Same for ECN and non-ECN flows.

7 NCA 2003 WPI Analysis of AQM #7 The General Queue Law

8 NCA 2003 WPI Analysis of AQM #8 General Queue Law Validation Used average TCP throughput mo del from (Padhye, Sigcomm 1998). Works well for ECN. Inaccurate for non-ECN: The TCP throughput model does not effectiv ely model Retransmission Timeout.

9 NCA 2003 WPI Analysis of AQM #9 Effect of Limiting TCP Window Window-limited (and short-lived) flows consume less bandwidth. Yet, they are less responsive to congestion notification

10 NCA 2003 WPI Analysis of AQM #10 Outline Introduction Queue Law Impact of ECN RED Family AQM Analysis of REDs Summary

11 NCA 2003 WPI Analysis of AQM #11 Impact of ECN on AQM ECN has no signaling packet loss. Requires higher CNP to keep the average queue at the same level. Helps the control system stability as less sensitive to CNP changes.

12 NCA 2003 WPI Analysis of AQM #12 Outline Introduction Queue Law Impact of ECN RED Family AQM Analysis of REDs Summary

13 NCA 2003 WPI Analysis of AQM #13 RED-Family AQM Queue law: p = g(q) Stable RED operating point p max th min th max p RED control function: p = h(q) 1 Random Early Detection (RED) q p q max th min th max p 1 Gentle RED 2 max th p q max th min th variable max p 1 Adaptive RED p q max th min th variable max p 1 Adaptive RED (w/ Gentle) 2 max th

14 NCA 2003 WPI Analysis of AQM #14 Simulation Configuration Dumbbell topology (SR = 20Mbps, Q = 500 pkts) Increase # of TCP flows (N = 50~300) each 50 sec. Implicit (drop) and ECN (configurations shown) p (300) max th (100) min th max p (0.1) q N=50N=100N=150N=200N=250N=300 rr s s s s s d d d d d SR = 20 Mbps max p limit (0.5) RTLD = 80 ms Q = 500 pkts

15 NCA 2003 WPI Analysis of AQM #15 Congested Router Queue (ECN Results)

16 NCA 2003 WPI Analysis of AQM #16 Packet Loss Rate

17 NCA 2003 WPI Analysis of AQM #17 Contribution The General Queue Law –Illustrated the effect of traffic parameters on AQM. –Discussed the impact of ECN traffic on AQM. –Provides mean to configure RED for ECN traffic. RED-Family AQM Evaluation –Showed the ECN gain on packet loss rate and the limitation of AQMs without ECN over Drop-Tail. –Provided an analysis on RED-Family AQM Gentle RED: may result in an unstable queue oscillation. Adaptive RED: can support a wide range of traffic loads.

18 NCA 2003 WPI Analysis of AQM #18 Future Work Extend our study to a mixture of ECN and non-ECN TCP flows. Building an adaptive AQM technique that makes use of our queue law to quickly adapt to a well-configured state in the presence of changing network loads.

19 Analysis of Active Queue Management Jae Chung and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA http://perform.wpi.edu/


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