ARQ Automatic Repeat reQuest (ARQ) is an error control method

ARQ
Automatic Repeat reQuest (ARQ) is an error control method for data transfer in which the receiver detects transmission errors in a message and automatically requests retransmission to the transmitter. When the transmitter receives the ARQ, the transmitter retransmits the message til it is correctly received or the error persists beyond a predetermined number of retransmissions
Choosy Repeat ARQ, is a specific instance of the Automatic Repeat reQuest (ARQ) Protocol, in which the sending process continues to send lots of frames specified by a window size even after a frame loss. dissimilar Go-Back-N ARQ, the receiving process will continue to recognize and acknowledge frames sent after an initial error.
The receiver process remains track of the sequence number of the earliest frame it has not received, and sends that number with every ACK it sends. If a frame from the dispatcher does not reach the receiver, the sender continues to send subsequent frames until it has emptied its window. The receiver maintains to fill its receiving window with the subsequent frames, replying each time with an ACK containing the succession number of the earliest missing frame. Once the sender has transmitted all the frames in its window, it resends the frame number given by the ACKs, and then continues where it left off.