Answer the following questions related to the FSMs for the Go-back-N protocol with m = 6 bits. Assume the window size is 63. (Figure 23.27):

a. The sending machine is in the ready state with S_f = 10 and S_n = 15. What is the sequence number of the next packet to send?
b. The sending machine is in the ready state with S_f = 10 and S_n = 15. A time-out occurs. How many packets are to be resent? What are their sequence numbers?
c. The sending machine is in the ready state with S_f = 10 and S_n = 15. An ACK with ackNo = 13 arrives. What are the next values of S_f and S_n?
d. The sending machine is in the blocking state with S_f = 14 and S_n = 21. What is the size of the window?
e. The sending machine is in the blocking state with S_f = 14 and S_n = 21. A_n ACK with ackNo = 18 arrives. What are the next values of S_f and S_n? What is the state of the sending machine?
f. The receiving machine is in the ready state with R_n = 16. A packet with sequence number 16 arrives. What is the next value of R_n? What is the response of the machine to this event?

Transcribed Image Text:

Figure 23.27 FSMS for the Go-Back-N protocol Sender Note: All arithmetic equations are in modulo 2" Request from process came. Make a packet (seqNo = S,). Store a copy and send the packet. Start the timer if it is not running. Sn = S +1. Time-out. Resend all outstanding packets. (S = Sy + Ssize" Restart the timer. Window full Time-out. Resend all outstanding packets. Restart the timer. [true] [false] Start -- Ready Blocking A corrupted ACK or an error-free ACK with ackNo outside window urrived. Error free ACK with ackNo greater than or equal to Spand less than S, urrived. A corrupted ACK or an crror-free ACK with ackNo less than Spor greater than or cqual to S arrived, Slide window (Sf = ackNo). If ackNo equals S stop the timer. If ackNo