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:
- 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.