Error control is both error detection and error correction. It allows the receiver to inform the sender of any frames lost or damaged in transmission and coordinates the re-transmission of those frames by the sender. In the data link layer, the term error control refers primarily to methods of error detection and re-transmission. Error control in the data link layer is often implemented simply: Any time an error is detected in an exchange, specified frames are re-transmitted. This process is called automatic repeat request (ARQ).