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: Find the total delay of the datagram.

Solution

Total delay to process the datagram=transmission time+propogation time+queuing and processing delay

Source->S1->S2->S3->S4->destination

From Source to S1 =no delay

From S1 to S2=transmission time+propogation time+queuing and processing delay

transmission time=data/data rate=5Mb/5Mbps=1sec

propogation time=length of cable/propogation speed=130*10³/3*10⁸=43.34*10^-5 sec

total delay from s1 to s2=1+43.34*10^-5+5*10^-3 sec=1005.433ms

From S2 to S3=transmission time+propogation time+queuing and processing delay

transmission time=data/data rate=5Mb/5Mbps=1sec

propogation time=length of cable/propogation speed=100*10³/10⁸=10^-3sec

total delay from s2 to s3=1+10^-3+15*10^-3 sec=1016ms

From S3 to S4=transmission time+propogation time+queuing and processing delay

transmission time=data/data rate=5Mb/10Mbps=0.5sec

propogation time=length of cable/propogation speed=100*10³/2.5*10⁸=0.4*10^-3sec

total delay from s3 to s4=0.5+0.4*10^-3+10*10^-3 sec=510.4 ms

From s4 to destination: queuing and processing delay of s4=25*10^-3sec=25ms

Total dealy=1005.433+1016+510.4+25ms=2556.833ms=2.55sec