DO-178/C permits virtual machine separation of function on shared computer hardware; this ("Special Conditions") is the first time
all three networks have been allowed to share a single network bus. Previously, networks were separated (primarily for historical reasons; the three network domains came aboard years apart; it made retrofitting features like seatback video screens easier on old aircraft) but that separation gave obvious safety benefits as well. Now, when building new airframes, Boeing quite rightly wants to avoid running three wires where one will serve, saving kilograms of mass.
But if we believe VM separation suffices for safety critical software, do we believe it as strongly for network traffic?