Programming
Problem 1 (19pts)
The diagram below shows the timing progress of a packet and ACK exchange to transfer 9 packets (each of size 2kB) between a sender and a receiver using a GoBack-3 rdt, over a network with throughput 10Mbps, loss-error probability of 5% and a round-trip duration of 2ms.
012345678
012 345678
012 345678
012345578
012345578
012345578
012345678
012345678
012345678 012345678 012345678 012345678 012345678
012345678 012345678 012345678 012345678 012345678 012345678 012345678 012345678
sender
Pkt Pkt
kt
rAt 0 tim Peout
pkt pkt Pkt pkt pkt
okt 2 tirneout
Pkt pkt pkt Pkt Pkt
pkt 4 t..Meout
Pkt
Pkt
Pkt
Pkt
Pkt
receiver
Ack
Ack
Ack
Ack
Ack
Ack
Ack Ack
Ack Ack Ack
Ack Ack
For the shown diagram: (13 pts)
Enumerate all the sent packets and ACKs in the diagram in accordance to the employed rdt scheme. (7.75 in total, 0.25pt for each packet/ack)
Explain what the receiver does with each received packet on the right of the diagram (Example: packet delivered or buffered or discarded).
Calculate the minimum number of sequence numbering bits that should be used in the transport layer header of this rdt scheme. (lpt)
All steps and mathematical formulae must be written.
Is the selection of the window size suitable with respect to the round-trip time of the network? Justify your answer. (1.5pts)
All steps and mathematical formulae must be written.
What is the minimum timeout duration that should be set for this rdt scheme over this network? (lpt)
All steps and mathematical formulae must be written.
What is the range of round-trip times on this network that justifies the use of a Stop-and-Wait rdt instead of the employed Go-Back-3 scheme? (2.5pts)
All steps and mathematical formulae must be written.
Highlight in each step the packets that are in the sender window on the left of the diagram. (5.25pt in total, 0.25pt for each packet)
