Stop and Wait

1. A transmitter transmits the frame.
2. Transmitter wait for the acknowledgement for fixed period of time.
3. On receiving valid frame, receiver send back an acknowledgement for next frame.
4. On receiving acknowledgement transmitter transmit next frame.
5. If sender not received any acknowledgement within time duration it re-transmit the same frame.
6. The rate of transmission depends on the processing power of the receiver.

Example of Stop and Wait protocol.

Frame Sender	Frame Receiver
Frame(0) transmitted	Acknowledgement Frame(1)
Frame(1) transmitted	Acknowledgement Frame(2)
Frame(2) transmitted	No Acknowledgement within time
Frame(2) re-transmitted	Acknowledgement Frame(3)

This method is ineffective when the size of the frame is large.

What if the size of the frame is large?

1. The transmitter divides large messages into smaller frames.
2. Then transmit these smaller frames.

---