Reliable transfer of communication is a critical requirement in communications between computers.One of them involves the ARQ ie Automatic Repeat re-Quest involves both identification of errors and retransmission to make sure that the data is received accurately by the user in spite of the various errors that occur during the transmission.
Stop and wait also known as bit banging protocol is one of the most simplest Automatic Repeat re-Quest method. In this method the sender sends one frame at a time and waits for an acknowledgment (ACK) from the receiver. If the receiver receives an uncorrupted frame an ACK is immediately sent. The errors in the frame are checked by the receiver using the redundancy bits added by the sender. Detection of an error is understood when the receiver does not send any ACK. In cases of errors the frame has to be resent to the receiver, but if the receiver does not respond when the error occurs the sender would not know if the frame has to be resent. In order to solve this the sender keeps a copy of the frame sent and starts of a timer once the frame is sent, if the sender does not receive the ACK within a specific duration of time (also known as time out) the sender sends the copy again.
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