Consider two packet switches directly connected by a link of 5000 km,
propagation speed 2.5 X10^8 m/s and transmission rate 1 Mbps. How long does it take to move
a packet of length 1,000 bytes from one packet switch to the other packet switch? Generally,
how long does it take to move a packet of length L over a link of distance d, propagation speed
s, and transmission rate R bps?