Automatic repeat-request
Automatic Repeat-reQuest (ARQ) is an error control method for data transmission which uses acknowledgments and timeouts to achieve reliable data transmission. An acknowledgment is a message sent by the receiver to the transmitter to indicate that it has correctly received a data frame. A timeout is a reasonable point in time after the sender sends the data frame; if the sender does not receive an acknowledgment before the timeout, it usually re-transmits the frame until it receives an acknowledgment or exceeds a predefined number of re-transmissions.
Types of ARQ protocol include Stop-and-wait ARQ, Go-Back-N ARQ and Selective Repeat ARQ.
A variation of ARQ is Hybrid ARQ (HARQ) which has better performance, particularly over wireless channels, at the cost of increased implementation complexity.
References
- Peterson and Davie, Computer Networks: A Systems Approach, Third Edition, 2003
ARQ can also stand for Admission Request in H.323 Registration, Admission and Status (RAS) messages
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