How to: Stop-and-Wait Protocols of Flow Control
- 1). Code the data link layer in the sender side to send a data frame, then block waiting for an acknowledgement and repeat the loop by sending the next frame. There is no need to have sequence numbers in the acknowledgments because an acknowledgment can only correspond to the last data frame sent out.
- 2). Code the data link layer in the receiver side to wait for the arrival of a data frame, then check that the frame was not corrupted in transit. Then send an acknowledgment frame back to the sender and repeat the loop by blocking again on the arrival of the next data frame.
- 3). Code a timeout on the receiver side if the network can lose packets. The receiver starts a timer when it sends the acknowledgment frame, and stops it when a data frame arrives. If the timer times out, the receiver re-sends the acknowledgment frame to the sender, thereby assuming that the last acknowledgment frame got lost in transit.
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