Automatic Repeat Request (ARQ)
- When the receiver receives transmitted data it must check for the presence of any errors. Errors can usually be detected but not always pinpointed
- An Automatic Repeat Request is a protocol that notifies the sender that an error has occurred and that the data received is incorrect. It works as follows:
- If an error is detected the receiver sends a negative acknowledgement transmission to indicate the data is corrupted
- If no error is detected the receiver sends a positive acknowledgement transmission meaning the data is correct
- If the receiver does not send any acknowledgement transmission then the sender waits for a certain time period known as a time-out before automatically resending the data
- This process is repeated until all data has been received and acknowledged
