Jonathan Shapiro and colleagues relate experience with a logically successful but underperformimg EROS implementation of the IP (Internet protocol) stack. EROS has largely the same domain state transition rules as Keykos.
There is a domain land driver which owns some pinned RAM pages. The driver knows details of the network interface card and exports minimal function to its clients while exposing necessary card function and performance. The driver holds authority to directly command the interface card. The driver keeps fixed size chronological circular buffers, one for input and one for output. We speak here about the input side which is not much different from the output side.
The wielders of the keys to the driver are programs that know intimate details about IP packets. These programs need to respond to their clients promptly and must respond even during periods after they have requested data from the driver and before that data has become available.