The NIC does not have the information required to make machine-wide optimal decisions about congestion control. It doesn't know what flows are critical at the a

The NIC does not have the information required to make machine-wide optimal decisions about congestion control. It doesn't know what flows are critical at the application level. NICs also can't know whether you want to optimize median or tail latency for a given flow. Only the application knows and that's where the congestion control algorithm needs to run.