$($b$)$ In "Stop and Wait" ARQ, the sender sends the next frame when an acknowledgement ACK frame is received from the receiver.

$($i$)$ Analyze the flow control of the "Stop and Wait" ARQ mechanism. Illustrate with a timing flow diagram, under which condition duplicate frames will be received undetected by the receiver.

$(5$ marks$)$

$($ii$)$ Following on from Question $2($b$)($i$),$ propose a simple improvement on the flow control protocol and illustrate that it allows detection of duplicate frames at the receiver.