Question

Now suppose there are four links between source and destination (three routers in the path between source and destination). Each link is 5,000 km long. Again suppose the file is sent as one packet. Suppose there is no congestion, so that the packet is transmitted onto the second link as soon as the router receives the entire packet. What is the end-to-end delay? (Hint: The router uses store-and-forward packet switching.)

Answer 1

Answer:

12.1 seconds

Explanation:

Step 1:

Assuming the following data :

N: Size of packet = 30 Mb

T: Transmission rate =  10 Mbps

C: Speed of light in copper = 2 * 10^8 m/s

L: Length of link 5000 km

Step 2:

Calculation of the Transmission delay and the Propagation Delay

Transmission delay = $\frac{packet size}{bandwidth}$ = $\frac{30Mb}{10Mbps}$ = 3s

Propagation delay = $\frac{length of link}{speed of light in copper}$ = $\frac{5000*10^3}{2 * 10^8}$ = 0.025s

Step 3:

Calculation of the end-to -end delay

The end-to-end delay = 4*(Transmission Delay+Propagation Delay) = 4*(3+0.025) = 12.1 seconds