This paper designs a robust active queue management (AQM) controller for IP routers based on the robust mu-analysis. Specifically, we synthesize the controller by modeling the uncertainty of the TCP/AQM system in the form of an uncertainty weight, and by approximating the mu-optimal control problem with the H-infinity S/T/U MSP (Mixed Sensitivity Problem). We also analyze the NP (Nominal Performance), the RS (Robust Stability) and the RP (Robust Performance) of the TCP/AQM system.