How to calculate the efficiency of a transmission link between two hosts in this question?
A two-way link has a data rate of 40 kb/s while transmitting data in either direction, and a propagation delay of 20 milliseconds in each direction. A is sending frames of L bits to B using stop-and-wait ARQ. A 160-bit acknowledgment frame is returned by B immediately after B receives a full frame of data from A. Define efficiency as the percentage of time that A is sending a frame of data. This ignores the additional inefficiency due to overhead in A’s frames.
What range of values of L gives an efficiency of at least 50% ?