Automatic Repeat Request Automatic repeat request (ARQ), also known as automatic repeat query, is an errorcontrol method for data transmission that uses acknowledgements and timeouts to achieve reliable data transmission over an unreliable service. If the sender does not receive an acknowledgment before the timeout, then re-transmits the frame/packet until the sender receives an acknowledgment. The types of ARQ protocols include Stop-and-wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ / Selective Reject. These protocols reside in the Data Link or Transport Layers of the OSI model.
