Assume we have the cumulative acknowledgment protocol with unbounded sequence numbers. Assume the channel can lose and reorder messages (but not duplicate). Furthermore, assume that the SWS = 1, and that the timeout of the sender is accurate,. i.e., the last action of the sender is replaced by

when timeout frame#ch.sender.receiver = 0 and ack#ch.receiver.sender = 0 and LAR < LFS then

     send frame(LAR+1) to receiver.

Under these conditions, is the sequence number in the acknowledgment really necessary? Briefly argue why yes or why no.