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Consider the store and forward packet switched network where host A and B are connected via 2 routers R1 and R2 .
Assume Transmission time to be 1ms and Propagation time of link to be 5ms. If a message is divided into 6 packets
of equal length then total time to transfer message is _________ ?
asked | 66 views
+1
23ms
0
Can you please explain
+2
Lets assume there are 6 packets $\left ( P_{1}, P_{2}, P_{3}, P_{4}, P_{5}, P_{6} \right )$

$P_{1}$  transmission from A  took 1ms then it will reach $R_1$ at 6ms then $R_2$ at 12ms then 6ms more to reach B from $R_2$. Hence $P_{1}$ took 18ms to reach host B.

Last packet $P_6$ is transmitted from A at 6ms then it will reach $R_1$ at 11ms then $R_2$ at 17ms then 6ms more to reach B from $R_2$. Hence $P_{6}$ took 23ms to reach host B.
+2
$1\times 3+5\times 3=18ms$ time for 1st packet to go destination

next 5 packet $5\times 1=5ms$ transmission time to reach destination

total 18+5=23ms

HERE FOR THE FIRST LINK BETWEEN SOURCE AND ROUTER 1 : TIME = 6*1 + 5 = 11

FOR REMAINING LINK WE USE CONCEPT OF PIPELINING.

BETWEEN ROUTER 1 AND ROUTER 2: TIME = 1 + 5 =6

BETWEEN ROUTER 2 AND DESTINATION: TIME = 1 + 5 = 6

-> TOTAL TIME = 11+6+6  = 23
answered ago by (213 points)
0
What if there was a buffer time of 2ms at each router , means packets will be forwarded after a wait of 2 ms and this is for each packet

+1 vote