Question

Consider the GBN protocol with a sender window size of 4 and a sequence number range of 1,024. 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: What are the possible sets of sequence numbers inside the sender’s window at time t? Justify your answer. 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.

Answer 1

Answer:

Follows are the solution to this question:

Explanation:

In point a:

N = Size of window = 4

Sequence Number Set = 1,024

Case No. 1:

Presume the receiver is k, and all k-1 packets were known. A window for the sender would be within the range of [k, k+N-1] Numbers in order

Case No. 2:

If the sender's window occurs within the set of sequence numbers [k-N, k-1]. The sender's window would be in the context of the sequence numbers [k-N, k-1]. Consequently, its potential sets of sequence numbers within the transmitter window are in the range [k-N: k] at time t.

In point b:

In the area for an acknowledgment (ACK) would be [k-N, k-1], in which the sender sent less ACK to all k-N packets than the n-N-1 ACK. Therefore, in all communications, both possible values of the ACK field currently vary between k-N-1 and k-1.