Computer Network

 

Consider a source S and a destination D using the Selective Repeat Protocol (SRP) with a window size of N=4N=4. Each packet is 10001000 bits.

The delays are as follows:

• Each packet transmitted by S has a transmission time of 10 ms10ms.
• The end-to-end delay from the time that S starts transmitting a packet until D completely receives that packet is 100 ms100ms.
• Each ack transmitted by D has a transmission time of 1 ms1ms.
• The end-to-end delay from the time that D starts transmitting an ack until S completely receives that ack is 100 ms100ms.
• The timeout value is 300 ms300ms.

Here is what happens to each packet:

• Packet #0 is received by D, and the corresponding ACK is received by S.
• The first transmission of packet #1 is dropped by a router in between S and D.
• The second transmission of packet #1 is received by D, and the corresponding ACK is received by S.
• The first transmission of packet #2 is dropped by a router in between S and D.
• The second transmission of packet #2 is received by D, and the corresponding ACK is received by S.
• Packet #3 is received by D, and the corresponding ACK is received by S.
• Packet #4 is received by D, and the corresponding ACK is received by S.
• Packet #5 is received by D, and the corresponding ACK is received by S.

(a) At time t = 150 mst=150ms, what is S's window?

(b) At what time does the retransmission of packet #1 start?

(c) At what time does the application layer at D receive packet #2?

(d) What is the throughput during the time from t = 0 mst=0ms until t = 500 mst=500ms?

Write your answers for parts (a)-(d) (as well as any diagram or equations use to obtain your answers) on paper, and upload the image here: