Because the number of transmission control protocol sessions usually varies from time to time, a perturbed Takagi-Sugeno fuzzy model is used in this paper to represent the dynamic transmission control protocol network systems. According to the proposed perturbed Takagi-Sugeno fuzzy model, a robust fuzzy controller design approach is investigated to achieve the congestion avoidance for the transmission control protocol network systems. In order to accomplish the above mission, some sufficient conditions are derived based on the Lyapunov stability theory. By solving these sufficient stability conditions, an active queue management router can be obtained via the proposed robust fuzzy congestion control technique.