Consider sending a file of F bytes over a path of Q links. Each link transmits a

Question

Consider sending a file of F bytes over a path of Q links. Each link transmits at R bps. The network is lightly loaded so that there are no queuing delays at any link. The propagation delay on each link is Tp seconds on average.

a) Suppose the network is a packet-switched virtual-circuit network. Assume the VC setup time is Ts seconds. Suppose the sending layers add a total of h bits of header to the file, and the size of each packet is P. How many packets are needed to send the file? How long does it take to send all the packets from source to destination?

b) Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose the size of each packet is P including 2h bits of header. How many packets are needed to send the file? How long does it take to send the file to its destination?

c) Finally, suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between source and destination is R bps. Assuming Ts setup time and h bits of header appended to the file, how long does it take to send the file to its destination?

Explanation / Answer

Answer:

a)

suppose file is contains K Packets and each packet having B bits.
Then time required to transfer one packet onto a link is (B + h)/R.
Now time required to trasfer a packet on Q links= Q(B + h)/R.
Hence total latancy to send the file from source to destination is

T= ts + K(B+h)/R + (K+h)(Q-1)/R

where
ts is VC setup delay
K(B+h)/R is a time to transmit the entire file between over the first node
(B+h)(Q-1)/R is the time to transmit the last packet over (Q-1) nodes

and here K packets are needed to send a file.

b)Here packet switched datagram service is used which does not required VC seup time.
Hence Total Latency T = K(B+2h)/R + (B+ 2h)(Q-1)/R

and here again K packets are needed to send a file.

c) Total Delay T= ts + (h+F)/R

Here No any queuing delay at the link as network is lightly loaded. Hence No any store and forward delays at link

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.