This is problem from my Networks class. It wants us to compute the round trip time of a point-to-point network and I'm just not sure which information is pertinent. The question:
NASA deployed its latest 622Mbps point-to-point laser link between Earth and a
new lunar base. The distance from the Moon to Earth is approximately 385,000 km, and data travels over the link at the speed of light 3 x 10^8 m/s.
(a) Calculate the minimum RTT for the link
I'm not sure whether I should be using the 622 Mbps or the distance and speed of light. My initial thought was using distance and speed of light. Meaning, the minimum would be (385,000*1000)m /(3x10^8 m/s)*2 = 2.56666 seconds.
But if you use the 622 Mbps you can compute, for the minimum it would be quickest if you only sent one bit, and the other host immediately responded with one bit meaning that the RTT would be 2*(1/(622*1,000,000)) = 3.215 e-9 seconds.
To me it seems like it should be the former, but if the link is 622 Mbps why would it take longer?
EDIT: to clarify don't tell me which answer is correct, as it is homework. I would like to understand the concepts involved with why RTT is unrelated to Mbps.