  Currently, Ethernet is broadly used in LAN, datacenter and enterprise
networks, storage networks, high performance computing networks and so on.
Along with the popularity of Ethernet comes the requirement of enhancing
Ethernet with congestion control. On the other hand, Ethernet speed extends to
40Gbps and 100Gbps recently, and even 400Gbps in the near future. The
ultra-high speed requires congestion control algorithms to adapt to the broad
changes of bandwidth, and highlights the impacts of small delay by enlarging
the bandwidth delay product. The state-of-art standard QCN is heuristically
designed for the 1Gbps and 10Gbps Ethernet, and unaware of the challenges
accompanying the ultra-high speed.
  To scale congestion control to ultra-high speed Ethernet, we propose the
Adaptive Sliding Mode (ASM) congestion control algorithm, which is simple,
stable, has fast and smooth convergence process, can tolerate the impacts of
delay and adapt to the wide changes of bandwidth. Real experiments and
simulations confirm these good properties and show that ASM outperforms QCN.
Designing ASM, we find that the derivative of queue length is helpful to rate
adjustment because it reflects the difference between bandwidth and aggregated
sending rate. We also argue for enforcing congestion control system staying at
the congestion boundary line, along which it automatically slides to stable
point. These insights are also valuable to develop other congestion control
algorithms in ultra-high speed networks.
