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Consider a source computer (S) transmitting a file of size 106 bit to a destination computer (D) over a network of two routers (R1 and R2) and three links (L1 , L2 and L3 ). L1 connects S to R1 ; L2 connects R1 to R2 and L3 connects R2 to D. Let each link be of length 100 km. Assume signals travel over each link at a speed of 108 m/s. Assume that the link bandwidth on each link is 1 Mbit/s. Let the file be broken down into 1000 packets each of size 1000 bits. Find the total sum of transmission and propagation delays in transmitting the file from S to D?
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- 1005 ms
- 1010 ms
- 3000 ms
- 3003 ms
- 1005 ms
Correct Option: A
Transmission delay for 1st packet from each of S, R1 and R2 will take 1 ms Propagation delay on each link l1 , l2 and l3 for one packet is 1 ms Therefore the sum of transmission delay and propagation delay on each link for one packet is 2 ms. The first packet reaches the destination at 6th ms The second packet reaches the destination at 7th ms So, inductively we can say that 1000th packet reaches the destination at 1005th ms.
