Consider the GBN protocol with a sender window size of 4 and a sequence number r

Question

Consider the GBN protocol with a sender window size of 4 and a sequence number range of 1024. Suppose that at time t, the next in-order packet that the receiver is expecting has a sequence number of “k”. Assume that the medium does not reorder messages. Answer the following questions:

1.What are the possible sets of sequence numbers inside the sender’s window at time t? Justify your answer.

2. What are all possible values of the ACK field in all possible messages currently propagating back to the sender at time t? Justify your answer.

Explanation / Answer

1) The reciever expects k....so ack are k-1,k-2,k-3,k-4. If none of ack are recieved by sender
then sender window will be (k-4,k-3,k-2,k-1). Acknowledgement k-5 will received by sender
.But if all ack are recieved then sender window will be (k,k+1,k+2,k+3)
So possibel sets are:
(k-4,k-3,k-2,k-1),(k-3,k-2,k-1),(k-2,k-1,k),(k-1,k,k+1),(k,k+1,k+2,k+3).

2)
Poosible values if Acknowledgement are:
as we already discussed in above solution, The possibilities are k-N-1 to k-1.

we will have possibilities are
k-1,k-2,k-3,k-4

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

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