Elementary Data Link Protocols-A simplex stop-and-wait protocol

Elementary Data Link Protocols-A simplex stop-and-wait protocol

A simplex stop-and-wait protocol

In this protocol we assume that Data are transmitted in one direction only No errors occur (perfect channel)
The receiver can only process the received information at a finite rate These assumptions imply that the transmitter cannot send frames at a rate faster than the receiver can process them. The problem here is how to prevent the sender from flooding the receiver. A general solution to this problem is to have the receiver provide some sort of feedback to the sender. The process could be as follows: The receiver send an acknowledge frame back to the sender telling the sender that the last received frame has been processed and passed to the host; permission to send the next frame is granted. The sender, after having sent a frame, must wait for the acknowledge frame from the receiver before sending another frame. This protocol is known as stop-and-wait.

The protocol is as follows:

/* protocol */

Sender()
{
        forever
        {
                from_host(buffer);
                S.info = buffer;
                sendf(S);
                wait(event);
        }
}

Receiver()
{
        forever
        {
                wait(event);
                getf(R);
                to_host(R.info);
                sendf(S);
        }
}