Assume that there is one router between a source and a destination (therefore th
ID: 3757963 • Letter: A
Question
Assume that there is one router between a source and a destination (therefore the
end-to-end path consists of a link from the source to the router, and a link from the router to the
destination). Each link is 100 km long. Suppose a file of size 4500 bytes is sent from the source to
the destination. The file fits in three packets. The router operates in store-and-forward mode.
Neglect processing delays and queueing delays, and make the following assumptions:
(i) The propagation delay across each link is 0.5 ms;
(ii) The per-packet transmission delay on each link is 12 microsec (s);
(iii) The path is error-/loss-free and so error control is not applied;
(iv) The source just divides the file into packets and sends the packets to the destination.
a. What is the propagation delay to send one bit across the end-to-end path?
b. What is the transmission delay incurred in sending all the packets of the file from the
source to the destination? [Hint: recall packet-level pipelining]
Explanation / Answer
Solution :
a) Propagation delay to send one bit across the end to end path :
dprop = ( m / s ) seconds = 3.05 seconds.
a) Transmission delay in sending all packets of file from source to destination :
dtrans = ( L / R ) seconds = 12 seconds.