Stop and wait ARQ is an error-control method that uses acknowledgements and timeouts to achieve reliable data transmission over an unreliable service. It works as follows: The transmitter sends a single frame and waits for a corresponding acknowledgement frame from the receiver before sending the next frame. If the acknowledgement is not received within a set time, the frame is retransmitted. Sequence numbers are used to identify frames and acknowledgements. The main advantages are that it provides both error and flow control, and uses timers to handle lost or corrupted frames. The main disadvantages are low efficiency since only one frame can be sent at a time, and overhead from setting timers for each individual frame. It is commonly used in protocols like B

1. STOP AND WAIT ARQSTOPWAITAND

2. Team membersDNAAabcNishitaAnanyaArchanaDhanusha Royston

3. Aayush

4. HimanshuAwesum4sumVinayakLishaAnitaPrabhaCaroline

5. Noiseless and Noisy Channels

6. STOP AND WAIT

7. Automatic Repeat reQuest Is an error-control method for data transmission

8. uses acknowledgements and timeouts to achieve reliable data transmission over an unreliable service.STOP AND WAIT ARQ

9. FramesPacketError Free PacketInformation FrameTransmitterReceiver Control FrameTimer is set after each frame transmission

10. Information FrameheaderInformation PacketCRCHeaderCRCAcknowledgement Frame

11. Sender-site algorithm for stop and wait ARQSn=0;Cansend=true;While(true){ Waitforevent() If(event(requesttosend)AND cansend) {Getdata();Makeframe(Sn);Storeframe(Sn)Sendframe(Sn);Starttimer()Cansend=false }

12. ContdWaitforevent(); if(event(arrivalnotification) {Receiveframe(ackno); If(ackno==Sn) {Stoptimer(); Purge(Sn-1);Cansend=true; } } If(event(timeout)) {Starttimer();Resendframe(Sn-1); }}

13. Receiver-site algorithm for Stop and Wait ARQRn = 0;While (true){WaitForEvent ( ); If (Event (ArrivalNotification) ) {ReceiveFrame ( ); If (corrupted (frame) ); sleep ( ); {ExtractData ( );DelieverData ( );Rn = Rn + 1; }SendFrame (Rn); }}

14. 0 10 10 10 10 10 10 10 1RnextSlastTimerSlastReceiver BTransmitter ARnext1-Bit Sequence Numbering Suffices Global State:(Slast, Rnext)Error-free frame 0arrives at receiver(0,0)(0,1)ACK forframe 0arrives attransmitterACK forframe 1arrives attransmitterError-free frame 1arrives at receiver(1,0)(1,1)

16. (a) Frame 1 lostTime-outTime AFrame 1Frame 1Frame 2Frame 0ACKACK B(b) ACK lostTime-outTimeAFrame 0Frame 1Frame 1Frame 2ACKACKACKBNeed for Sequence Numbers

17. Sequence NumbersTime-outTimeAFrame 0Frame 2 Frame 0Frame1ACKACKB(c) Premature Time-out

18. Advantages and disadvantages of Stop and Wait ARQ

19. Advantages of Stop and Wait ARQ over simple Stop and Wait protocolIt can be used for noisy channelsIt has both error and flow control mechanismIt has a timer implementation

20. Disadvantages of Stop and Wait ARQ Efficiency is very less.

21. Only 1 frame is sent at a time.

22. Timer should be set for each individual frame. No pipelining.

23. Sender window size is 1 ( disadvantage over go back n ARQ). Receiver window size is 1 ( disadvantage over selective repeat ARQ).

24. ApplicationsIBM Binary Synchronous Communication Protocol (Bisync): Character-oriented data link control.Xmodem: Modem file transfer protocol.Trivial file transfer protocol (RFC 1350): simple protocol for file transfer over UDP.

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