Diffusion marking mechanisms for active queue management

Active queue management (AQM) schemes proposed to date use control mechanisms having fundamental weaknesses often leading to overparameterization and instabilities. This paper draws from the rich theory of dithering and quantization, extensively used in signal processing, to develop new marking and control mechanisms that overcome such limitations. In particular, a packet marking mechanism is developed through error diffusion filtering where congestion is measured and controlled through the instantaneous queue, the derivative of the queue length, and an estimate of the number of active flows. The proposed mechanism, referred to as DM (diffusion marking), is able to maintain a desired average queue length even under rapid changes in the traffic dynamics with surprisingly short lived queue size transients. DM provides a consistent low link delay without sacrificing throughput and is shown to outperform RED, REM, and AVQ type AQM mechanisms in varying network conditions with a significant improvement in stability.