In the field of networking and data transmissions, ARQ or automatic repeat requests are data transfer protocols that setups up an automatic request for re-transmission of data every time an error is detected. Under normal conditions, the transfer of data from one location to another is made through chunks or data packets. The bigger the data, the more packets will be transferred from the source to the receiving station. When any of these packets are incomplete or contain errors, the ARQ protocol will instantly and automatically create another request to make sure that the data source will send again the data packet that contains the error. The automatic repeat request will run over and over again as data is transmitted from the source to the receiver until such time that all the data packets received contain no errors or are not corrupted. The ARQ protocol may only stop if a pre-determined cycle is configured for the data transfer system. With this pre-determined cycle, data transmission will be dropped or reset if the ARQ is run to its maximum.

The basic purpose of having and ARQ or automatic repeat request protocol in place is to ensure the integrity of data. With data being divided into different chunks and sent as packets from the source computer to the receiving terminal, the chance of loss and corruption will always be present. In most cases, data loss or corruption may occur because of poor transmission signals. When there is a problem with the communication line from the source server for example down to the receiving terminals or end-user units, errors are expected to occur during data transmission. With these errors, data integrity may be loss. Possible errors on the data packets may also occur when there is limited bandwidth available for the transfer. This concern happens when there is too much data being transferred simultaneously. In this concern, the ARQ protocol may run over and over again but will still be unsuccessful in terms of data integrity.