Question

In a packet switching network, packets are routed form source to destination along a single path having two intermediate nodes. If the message size is 24 bytes and each packet contains a header of 3 bytes, then the optimum packet size is

• A. 4
• B. 7
• C. 9
• D. 6

Answer 1

The correct option is C 9

Let S denotes the source station and D denotes the destination station . x and y are two intermediate nodes between S and D.
$\begin{array}{cccc}\cdot & \cdot & \cdot & \cdot \\ S& x& y& D\end{array}$
Message size = 24 bytes, Header (control information ) = 3 bytes consider the first choice (a).
Packet size = 4 then message size = 4-3 =1 byte so it required 24 messages each contaminating 3 bytes header so the transmission time for header overhead increases. Consider the second, third and fourth choices.
(b) Packet size = 6 then message size
= 6-3 = 3 bytes (required 8 packets)
(c) Packet size = 7 then message size
= 7-3 = 4 bytes (Required 6 packets)
(d) Packet size = 9 then message size.
= 9-3 = 6 bytes (Required 4 packets)
So 4 packet is the optional message size & 9 is the optional packet size.