In a datagram network shown in the figure below the source i

In a datagram network shown in the figure below, the source is directly connected to Switch 1 and the destination is directly connected to Switch 4, and thus there is no delay between source and Switch 1, and between Switch 4 and destination. A datagram of 5M bits is sent from Source to Destination, through the route of S1 rightarrow S2 rightarrow S3 rightarrow S4. Suppose that the delays for switches 1 to 5 (including queuing and processing delays) are 5, 15, 10, 25. and 5 ms, respectively. Communication links between switches are not identical and have the following characteristics:

Solution

Answer:

Total delay in transmitting a datagram can be expressed as:

Total delay=Total propagation delay+Total transmission delay+Total prosessing delay

For the give scenario(S1->S2->S3->S4):

Total propagation delay=propagation delay for (S1->S2)+propagation delay for (S2->S3)+propagation delay for (S3->S4)

= (distance(S1->S2)/progation speed) + (distance(S2->S3)/progation speed)+(distance(S3->S4)/progation speed)

= (130*1000)/(3*10^8)+(100*1000)/(1*10^8)+(100*1000)/(2.5*10^8)

=(0.4333+1+0.4)*10e-3=1.8333*10e-3 s = 1.8333 ms

Total transmission delay=transmission delay for (S1->S2) + transmission delay for (S2->S3) + tranmission delay for (S3->S4)

= datagram size/transmission speed for (S1->S2)+datagram size/transmission speed for (S2->S3)+datagram size/transmission speed for (S3->S4)

=5M/5Mbps+5M/5Mbps+5M/10Mbps

=1+1+0.5=2.5 s=2500 ms

Total processing delay=processing delay for S1+processing delay for S2+processing delay for S3+processing delay for S4

=5+15+10+25=55 ms

Hence, for given scenario,

Total Delay =1.8333+2500+55=2556.8333 ms