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:
a. What are the possible sets of sequence numbers inside the sender’s win- dow at time t? Justify your answer.
b. What are all possible values of the ACK field in all possible messages cur- rently propagating back to the sender at time t? Justify your answer.