Implementation of PI2 Queuing Discipline for Classic TCP Traffic in ns-3

Abstract

This paper presents the implementation and validation of PI2 Active Queue Management (AQM) algorithm in ns-3. PI2 provides an alternate design and implementation to Propor- tional Integral controller Enhanced (PIE) algorithm without affecting the performance benefits it provides in tackling the problem of bufferbloat. Bufferbloat is a situation arising due to the presence of large unmanaged buffers in the network. It results in increased latency and therefore, degrades the performance of delay-sensitive traffic. PIE algorithm tries to minimize the queuing delay by auto-tuning its control param- eters. However, with PI2, this auto-tuning can be replaced by just squaring the packet drop probability. In this paper, we implement a model for PI2 in ns-3 and verify its correctness by comparing the results obtained from it to those obtained from the PIE model in ns-3. The results indicate that PI2 offers a simple design and achieves similar responsiveness and stability, and in some cases, better than PIE.