Pipelining
Let us now imagine trying to use protocol 4 to send 1000-bit frames via a 50-kbps satellite link with a 500-msec round-trip time
t= 0 msec : sender starts sending the first frame
t= 20 msec : first frame sent
t= 270 msec : first frame arrives at receiver
t= 520 msec : acknowledgement for arrives at sender
Note : it is (unrealistically) assumed that the processing time at the receiver is 0 msec