Robust Lyapunov–Krasovskii based design for explicit control protocol against heterogeneous delays

TCP has been extensively credited for the stability of the Internet. However, as the product of bandwidth and latency increases, TCP becomes inefficient and prone to instability. The explicit control protocol (XCP) is a promising congestion control protocol that outperforms TCP in terms of efficiency, fairness, convergence speed, persistent queue length and packet loss rate. However, XCP is not globally stable in the presence of heterogeneous delays. When the ratio of maximum to average transmission latency is sufficiently large, XCP will become instability. In this paper, according to the robust control theory, with the help of a recently developed Lyapunov–Krasovskii functional, an improved version of XCP, named R-XCP, is proposed to solve the weakness of XCP under heterogeneous delays, which adjusts parameter $$\alpha $$ α from an initial value of 0.4 to a reasonable value for improving system robustness. And then, the synthesis problem is reduced to a convex optimization scheme expressed in terms of linear matrix inequalities. Extensive simulations have shown that R-XCP significantly decreases the volatilities of the aggregate traffic rate and control time interval, and indeed achieves this stability goal. Compared with previous work, R-XCP has a better balance between robustness and responsiveness, and the computational complexity declines significantly at the same time. Besides, R-XCP makes the system less sensitive to flows, which contribute little traffic but maliciously report their transmission delays.