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 J 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 sent from Source to Destination, through the route of S_1 rightarrow S_2 rightarrow S_3 rightarrow S_4. 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

Datagram delay is given by:

ML + NT + (M-1)T + (M-1)P

where M = number of hops

P = per hop processing delay

L = Link propagation delay

T = packet transmission delay

N = message size

Delay from 1 to 2:

M = 1

N = 1

P = 5ms

L = distance/speed = 130*1000/3*10⁸ = 0.433 ms

Packet size = 5*1024*1024 bits

T = packet size/ transmission speed = 5M/5M = 1 s

Delay = ML + NT + (M-1)T + (M-1)P = 0.433 ms + 1s + 0 + 0

= 1000.433 ms

Delay For 2-3 (Applying same formula as above):

= 1 ms + 1 s = 1001 ms

Delay for 3-4:

= 0.4 ms + 0.5 s = 500.4 ms

Delay because of switches = 5 + 15 + 10 + 25 = 55 ms

Therefore, total delay = 1000.433+1001+500.4+55

= 2556.833 ms