Analysis and design of improved PI-PD controller for TCP AQM routers

Active Queue Management (AQM) plays a very important role in congestion control of Transmission Control Protocol/Internet Protocol (TCP/IP) networks. This paper attempts to design an improved proportional-integral-proportional-derivative (PI-PD) controller as an active queue manager for TCP routers. The proposed controller scheme controls present congestion reactively and also avoids the incipient congestion proactively. Fast response to the changing traffic is achieved by PD as it maintains the target queue length, high link utilization and low packet loss. We use ns simulation to demonstrate the practical advantage of using PI-PD controller over PI in managing queue utilization and delay.