Robust Explicit Congestion Controller Design For High Bandwidth-Delay Product etwork: A H∞ Approach

TCP becomes inefficient and prone to instability when its bandwidth-delay product increases. By sending explicit congestion information from routers to end hosts, both XCP and API-RCP have been proposed to solve the stability issue of TCP in high bandwidth-delay product networks. Since the estimation errors of the network parameters are unavoidable, we would like to design a robust controller to address this type of model uncertainty in the explicit congestion control system. We employ the H∞ optimal criterion in our design, and select a proper weight function to solve the H∞ sensitivity problem. By using the maximum modulus theorem from the robust control theory, we obtain an optimal internal model controller from which a robust H∞ controller can be derived. OP ET simulations demonstrate that our H∞ controller exhibits a good robustness to varying network parameters. Performance comparison between our robust explicit congestion controller and TCP/RED is provided. Index Items—Explicit Congestion Control, Model Uncertainty, Robust Control, H∞ optimal criterion, TCP/RED