Propagation Delay

Question

Consider a communication link between a workstation which is on earth and a satellite which acts as a server. Distance between earth and satellite is 4 * 10^4 km. What is the best-case delay in response to a request?

Comments

is it 2d/v where d is given and v =3*10^8.... since response time would be request from earth is to satellite and then response from satellite to earth... that's y 2*propagation time

Answer 1

Explanation:
The request must go up and down (request and acknowledgment), and the response must go up and down (response and acknowledgment).
Therefor, For a simple request and response, total 4 packets(request, ack, response, ack) has to travel the entire distance.
So total distance (d) covered for a complete request and response communication is
2 * (4*10^4) Km.
Therefore, the propagation delay is d/v = 80,000/300,000 sec = 0.02666 sec =26.66 ms.