Time-optimal controller for AQM router supporting TCP flows with small RTT

Active queue management (AQM) is an effective method to enhance congestion control, and to achieve tradeoff between link utilization and delay. Recently it has shown that the active queue management schemes implemented in the routers of communication networks supporting transmission control protocol (TCP) flows can be modeled as a feedback control system. In this paper, based on Lyapunov function we developed an optimal controller for small RTT TCP flows to improve active queue management router´s stability and response time, which are often in conflict with each other in system performance. Using ns simulations, it is shown that optimal controller outperform PI controller significantly.