Go Back N ARQ

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Go Back N ARQ

  1. 1. GO- BACK N ARQ<br />TEAMS:<br />BANDWIDTH BROTHERS<br />DEADLOCK<br />FOSTERS<br />NEW CREATORS<br />ROTHMANS<br />
  2. 2. INTRODUCTION<br />CONCEPT OF PIPELINING<br />IMPROVING THE EFFICIENCY OF TRANSMISSION<br />WHY ITS CALLED GO- BACK N ARQ<br />CONCEPT OF SEQUENCE NUMBERS, SLIDING WINDOW, TIMERS ,ACKNOWLEDGEMENT AND RESENDING FRAME. <br />
  3. 3. DISADVANTAGES OF STOP AND WAIT<br />1) Efficiency is very less if channel is thick and long.<br /> Thick means channel has large bandwidth.<br /> Long means the round trip is delay product of these <br /> two is called bandwidth delay product...<br />2) There is no pipelining because we need to wait for a frame to reach the destination and be acknowledged before the next frame can be sent.<br />
  4. 4. PIPELINING<br />In networking if a task is often began before the previous task ended. This is known as PIPELINING.<br />
  5. 5. SLIDING WINDOW<br /><ul><li>SEND SLIDING WINDOW
  6. 6. RECEIVE SLIDING WINDOW</li></li></ul><li>Send window before sliding<br />Sf<br />Sn<br />
  7. 7. Send window after sliding<br />Sf<br />Sn<br />
  8. 8. Receive window before sliding<br />Rn<br />
  9. 9. Receive window after sliding<br />Rn<br />
  10. 10. Delay component in ARQ<br /><ul><li>Time to send frame and get ACK.
  11. 11. Effective transmission ratae.
  12. 12. Transmission efficiency.</li></li></ul><li>SENDER WINDOW<br />
  13. 13. RECEIVER WINDOW<br />
  14. 14. PIGGYBACKING<br />Control signal is attached with Data signal.<br /> Request Window  Sender Window<br /> Arrival Window  Both Window {Data, Control}<br />Used to improve the efficiency of the Bidirectional Protocol.<br />Carries control information about arrival or lost frames<br />Both Sender and the Receiver window use a timer and are involved in three types of events.<br /> Request.<br /> Arrival.<br /> Time-out.<br />Both site must use the same Algorithm.<br />
  15. 15.
  16. 16. Go-Back-N Error Recovery<br />The recovery of a corrupted Frame proceeds in three stages:<br /><ul><li>First, the corrupted frame is discarded at the remote node's receiver.
  17. 17. Second, the remote node requests retransmission of the missing frame using a control frame (sometimes called a NACK or REJECT). The receiver discards all frame s which do not have the number of the requested frame.
  18. 18. The final stage consists of retransmission of the lost frame(s).</li></li></ul><li>ADVANTAGES OF GO-BACK NARQ<br />The sender can send many frames at a time.<br /> Timer can be set for a group of frames. <br /> Only one ACK can acknowledge one or more frames. <br /> Efficiency is more. <br />Waiting time is pretty low. <br />We can alter the size of the sender window<br />
  19. 19. DISADVANTAGES OF GO-BACK N ARQ<br />Buffer requirement:<br />Transmitter needs to store the last N packets<br />Scheme is inefficient when round-trip delay large and data transmission rate is high<br />Retransmission of many error-free packets following an erroneous packet<br />When RTT is large: for a high number of NACK, a lot of BW is wasted<br />If NACK is lost , a long time is wasted until re-transmission of all packets (until another NACK is sent).<br />
  20. 20. Selective Repeat ARQ<br />To overcome the disadvantages of GO BACK N ARQ, we use Selective Repeat ARQ<br />To utilize more bandwidth<br />
  21. 21. COMPARISON CHART<br />
  22. 22. THANK YOU<br />

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