Case Scenario

Data packet generated from an email typed by Alice is to be sent to Bob on a Packet Switched Network with two

intermediary nodes $1$ and $4.$ The original size of the packet is $40$Bytes. The packet header size is $3$Bytes. Scenario a$,$

b$,$ c$,$ and d depict network situations in which the data packet has been either fragmented or not fragmented.

Let A denote Alice$$s computer and let B denote Bob$$s computer.

Let node $4$ and node $1$ be intermediary network devices between A and B$.$

Let the hop$-$to$-$hop Network Bandwidth be $1$Byte per second $(1$Bps$).$

Assume that the propagation delay and switching time are negligible $($i$.$e$.,$ no delay$)$

Assume that processing time at all nodes are equal.

Assume that packets are fragmented into equal sizes

Scenario a: shows that the original packet to be transmitted has not been fragmented.

In scenario a$,$ the data packet that is sent from A to B is unfragmented. Total size of a transmitted data packet $=40$ Bytes $($packet$)+3$ Bytes $($header$)=43$ Bytes

Hop to hop Network bandwidth is $1$Bps$,$ so the time it will take to transmit the email from hop to hop is $43$ seconds. Now, the total transmission time from A to B $=43$seconds $($from A to node $4)+43$ seconds $($from node $4$ to node $1)$

$+43$ seconds $($from node $1$ to B$).$ This means that:

$43$ Bytes is transmitted in $43$ seconds from A$$node $4$

$43$ Bytes is transmitted in $43$ seconds from node $4$ node $1$

$43$ Bytes is transmitted in $43$ seconds from node $1$ B

So$,$ the transmission from A to B takes a total of $43$ x $3=129$seconds.

Therefore, the network will use $43+43+43=129$ seconds if email data packet is unfragmented.

Scenario b: shows that the original packet to be transmitted has been fragmented into $2$ equal sizes.

In scenario b$,$ the data packet that is sent from A to B is fragmented into $2$ equal sizes.

Total size of a transmitted data packet $=20$ Bytes $($packet$)+3$ Bytes $($header$)=23$ Bytes

Hop to hop Network bandwidth is $1$Bps$.$

Scenario c: shows that the original packet to be transmitted has been fragmented into $5$ equal sizes.

Scenario d: shows that the original packet to be transmitted has been fragmented into $10$ equal sizes.

Questions:

$1.$ Find the end$-$to$-$end transmission time of the email data packet from Alice$$s computer to Bob$$s computer if the network$$s operation is based on scenario c and d$.$

$2.$ Use your observation of all these scenarios to explain why or whether these statements are true or not.

a$)$ If bandwidth is higher, the transmission time will be less.

b$)$ If the packet size increases, the transmission time will also increase.

$3.$ Use your observation of all these scenarios to explain why or whether these statements are true or not.

a$)$ Fragmenting data packets decreases transmission time?

b$)$ If fragmented data packet gets too small, transmission time begins to increase.