Active Queue Management in Internet and Wireless NetworksX. Deng, S. Yi, G. Kesidis and C. R. Das

The Pennsylvania State University

• Stabilized queue size with varying traffic loads and link delays• Reduced packet loss and response time

• A Unified Framework for Design and Analysis of AQM • Interpreting and Calibrating AQM parameters as PID controlling components to the TCP plant module.• New Controlling Components in AQM• Derivative Control (D control): Use change of packet arrival rate over time as the congestion indicator, in addition to the instantaneous packet arrival rate (P control) and router queue length (I control).• Adaptive Control: The controlling parameters adaptively changes with the steady state packet marking probability p0 using update functions m and l, which increase monotonically (APID).

• Virtual Queue Control: A New Combination of rate-based and queue-based control (QRVQ)

Modeling TCP/AQM• A control-theoretic model for TCP and RED [Hollot’01].• Extend this model to incorporate more end-system and AQM controller

• Proportional-Integral-Derivative (PID) controller – A unified framework for design and analysis of AQM schemes. • System stability is related to network and traffic condition – use Adaptive Control for a better stabilized and robust system

AQM for Wireless Networks• More variable in bandwidth and delay• Uplink/Downlink asymmetry

ABSTRACT

MOTIVATION

METHOD

RESULTS

CONCLUSIONS

Queue AQM

TCP-Reno

FIFO

In this research, we use a control theoretic approach to develop a generic framework for analyzing various active queue management (AQM) schemes as proportionally-integral-derivative (PID) controllers. Based on this PID model, we propose an adaptive control mechanism to improve the system stability and performance under changing network conditions. A simulation study under a wide range of traffic conditions suggests that the proposed algorithms outperform the existing AQM schemes in achieving better system performance and stability. We then apply the AQM concept to achieve fairness bandwidth allocation between downlink and uplink traffic in wireless LANs

Queue

TCPdynamic

queuedynamic

AQM

RN

p

W q

time delayR secs

• Better Fairness between uplink/downlink traffic by using PI control over packet arrival rate (AVQ) for uplink traffic in Wireless LAN

•N: Number of connections

•W: TCP congestion window

•R: Round trip time

• : Packet arrival rate

•q: router queue size

•p: packet drop/mark probability

• Putting everything together :

)( pmq pcG )( 0pl

cc GplG )( 0

-1

Gt Gqqp

Cs

C

p01

-

METHOD (CONT)

Use Rate-based AQM for Uplink Traffic in Wireless LANs• Ensure fairness for downlink/uplink traffic• Can work together with downlink queue-based AQM for Queue management and QoS provisioning

Linearized TCP/AQM System

-1

AQM(Gc) TCP (Gt) Queue (Gq)

Plant (Gp)Controller

qp

rate based

-1

AQM(Gc) TCP (Gt) Queue (Gq) qp

-1AQM(Gc)

TCP (Gt)

p

DownlinkDownlink

UplinkUplink

• Various AQM Schemes can be classified as different types of PID Controllers.• Addition of derivative and adaptive control improves the stability of the system under varying plant configurations.• A rate based AQM for uplink traffic in Wireless LANs enhances the fairness and improves the QoS for downlink traffic.

No AQMNo AQM With AVQWith AVQ

sKs

KKG D

IPC

SYSTEM MODEL