Automatic Repeat reQuest (ARQ), also known as Automatic Repeat Query, is an error-control method for data transmission that uses acknowledgements (messages sent by the receiver indicating that it has correctly received a data frame or packet) and timeouts (specified periods of time allowed to elapse before an acknowledgment is to be received) to achieve reliable data transmission over an unreliable service. If the sender does not receive an acknowledgment before the timeout, it usually re-transmits the frame/packet until the sender receives an acknowledgment or exceeds a predefined number of re-transmissions.
The types of ARQ protocols include
- Stop-and-wait ARQ
- Go-Back-N ARQ
- Selective Repeat ARQ
These protocols reside in the Data Link or Transport Layers of the OSI model.
A number of patents exist for the use of ARQ in live video contribution environments. In these high throughput environments negative acknowledgements are used to drive down overheads.
Read more about Automatic Repeat Request: Examples
Famous quotes containing the words automatic, repeat and/or request:
“What we learn for the sake of knowing, we hold; what we learn for the sake of accomplishing some ulterior end, we forget as soon as that end has been gained. This, too, is automatic action in the constitution of the mind itself, and it is fortunate and merciful that it is so, for otherwise our minds would be soon only rubbish-rooms.”
—Anna C. Brackett (1836–1911)
“The experience of a sense of guilt for wrong-doing is necessary for the development of self-control. The guilt feelings will later serve as a warning signal which the child can produce himself when an impulse to repeat the naughty act comes over him. When the child can produce his on warning signals, independent of the actual presence of the adult, he is on the way to developing a conscience.”
—Selma H. Fraiberg (20th century)
“Were all the worshippers of the gold calf to memorialize me and request a restoration of the deposits I would cut my right hand from my body before I would do such an act. The gold calf may be worshipped by others but as for myself I serve the Lord.”
—Andrew Jackson (1767–1845)