Simplex stop-and-wait protocol
Eliminates the assumption that there is an infinite buffer space in the DLL in which to store all incoming frames.
Assume communication channel is error free and data traffic is one way (more later).
Therefore we only have to worry about how not to flood the receiver.
If the receiver requires ?t (seconds, microseconds etc) from_physical_layer and to_network_layer then sender must send less than one frame per ?t.