In this paper we rethink the tradeoff between proportional controller and PI controller in AQM (Active Queue Management) algorithm design. With the introduction of integral factor, the steady state error in proportional controller such as RED is eliminated. However, the integral factor also slows down the response speed. We present a simple algorithm P 2 I to solve this problem. P 2 I combines the advantage of proportional controller and PI controller. The performance of P 2 I is verified and compared with PI controller using ns-2 simulations. P 2 I is shown to response much faster than PI controller while keeping the merit of PI controller. We also analyze the big impact of traffic pattern on the design and success of AQM.