Fragility via Robustness of Controllers Dedicated to the Congestion Control in Internet Protocol

Success of a control design is usually measured by the robustness and optimality of the controller obtained, however, these designs can produce extremely fragile controllers, in the sense that small perturbations of the coefficients of the controller can destabilize the closed loop system. In previous papers, we have described several approaches, such as modern control theory, the norms H2/H infinity, Kharitonov approach and Quantitative feedback Theory, for the design of robust and optimal controllers developed for the treatment of the congestion control problem in Internet Protocol. In this work, we show by examples that optimum and robust controllers designed should aware those contemplating the design of real systems using these methods.