Question

Data communications requires at least two devices working together, one to send and one to receive.

Data Link Layer are responsible for creating frames, flow control and error control.

In the transmission of frame, we can have four situations: normal operation, the frame is lost, the acknowledgment is lost, or the acknowledgment is delayed.

For the above reason, FRAMES from a sending station are numbered sequentially.

Find the explanation of Stop-And-Wait ARQ of data link control.

Please answer this question in detail and clearly.

Answer 1

In stop and wait protocal,problems are frame is lost ,acknowledgment is lost , or the acknowledgement is delayed.

To avoid above problems,Stop and wait ARQ(automatic repeat request) has the following Elements

1.Timer

2.Sequence numbers for data packets

3.Sequence numbers for acknowledgements

Timer is set to some value for sending packets.If acknowledgement is not produced with in that time then automatically sender re transmits the packet and reset the timer to avoid deadlock problem which was there in stop and wait protocol.

If frame is lost then the receiver will send request in the form of acknowledgement to send particular number packet and sender will re transmit the packet by setting time.So,Sequence numbering of packets will not create a problem of losing packet in the receiver after getting all packets.Finally,they are arranged in order ed sequence in the receiver to get original ordered complete information.

Finally,We can say that

Stop and wait ARQ=Stop and wait protocol+sequence number of packets+sequence number of acknowledgements.