What is Stop-and-Wait Protocol?
Stop and wait protocol is used to send information between connected devices. The sender transmits one packet and waits for an acknowledgment (ACK) from the receiver before transmitting the next packet. When the ACK is received, the sender acknowledges that the packet is sent successfully and then transmits the next packet.
The sender keeps record of each packet it sends. To avoid confusion which can be caused by delayed or duplicated ACKs, in the stop and wait protocol the sender sends each packets with unique sequence numbers and verifies that number when it receives each ACK.
If the ACK is not received after a certain period of time for the previous sent packet, the sender times out and retransmits that packet again.