Find the total sum of transmission and propagation delays in transmitting the file using sliding window concept.

Consider a source computer (S) transmitting a file of size 106106 bits 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; L2connects 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 meters per second. Assume that the link bandwidth on each link is 1 Mbps. 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? 

(A) 1005 ms 
(B) 1010 ms 
(C) 3000 ms 
(D) 3003 ms

1Comment
Habib Mohammad Khan @habibkhan
6 Sep 2017 10:46 am

Its based on pipelining concept which says :

Let the one packet travel from source to destination and thereafter every transmission time interval the next packet will also reach the destination..

So time taken by 1st packet  = 3 * Tt(Data needs to be put into source end, router 1 and router 2) + 3 * Tp (There are 3 links in between)  

                      =  3 * (packet size/bandwidth) + 3 * (link length/velocity of link)

Having found that , as said earlier now at each transmission time interval , one by one 999 packets will be received at destination end..

So for that we need   =  999 Tt

So total time needed  =  3Tp  +  1002 Tt