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Go Back N ARQ

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  • 1. GO- BACK N ARQ
    TEAMS:
    BANDWIDTH BROTHERS
    DEADLOCK
    FOSTERS
    NEW CREATORS
    ROTHMANS
  • 2. INTRODUCTION
    CONCEPT OF PIPELINING
    IMPROVING THE EFFICIENCY OF TRANSMISSION
    WHY ITS CALLED GO- BACK N ARQ
    CONCEPT OF SEQUENCE NUMBERS, SLIDING WINDOW, TIMERS ,ACKNOWLEDGEMENT AND RESENDING FRAME.
  • 3. DISADVANTAGES OF STOP AND WAIT
    1) Efficiency is very less if channel is thick and long.
    Thick means channel has large bandwidth.
    Long means the round trip is delay product of these
    two is called bandwidth delay product...
    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.
  • 4. PIPELINING
    In networking if a task is often began before the previous task ended. This is known as PIPELINING.
  • 5. SLIDING WINDOW
    • SEND SLIDING WINDOW
    • 6. RECEIVE SLIDING WINDOW
  • Send window before sliding
    Sf
    Sn
  • 7. Send window after sliding
    Sf
    Sn
  • 8. Receive window before sliding
    Rn
  • 9. Receive window after sliding
    Rn
  • 10. Delay component in ARQ
    • Time to send frame and get ACK.
    • 11. Effective transmission ratae.
    • 12. Transmission efficiency.
  • SENDER WINDOW
  • 13. RECEIVER WINDOW
  • 14. PIGGYBACKING
    Control signal is attached with Data signal.
    Request Window  Sender Window
    Arrival Window  Both Window {Data, Control}
    Used to improve the efficiency of the Bidirectional Protocol.
    Carries control information about arrival or lost frames
    Both Sender and the Receiver window use a timer and are involved in three types of events.
    Request.
    Arrival.
    Time-out.
    Both site must use the same Algorithm.
  • 15.
  • 16. Go-Back-N Error Recovery
    The recovery of a corrupted Frame proceeds in three stages:
    • First, the corrupted frame is discarded at the remote node's receiver.
    • 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. The final stage consists of retransmission of the lost frame(s).
  • ADVANTAGES OF GO-BACK NARQ
    The sender can send many frames at a time.
    Timer can be set for a group of frames.
    Only one ACK can acknowledge one or more frames.
    Efficiency is more.
    Waiting time is pretty low.
    We can alter the size of the sender window
  • 19. DISADVANTAGES OF GO-BACK N ARQ
    Buffer requirement:
    Transmitter needs to store the last N packets
    Scheme is inefficient when round-trip delay large and data transmission rate is high
    Retransmission of many error-free packets following an erroneous packet
    When RTT is large: for a high number of NACK, a lot of BW is wasted
    If NACK is lost , a long time is wasted until re-transmission of all packets (until another NACK is sent).
  • 20. Selective Repeat ARQ
    To overcome the disadvantages of GO BACK N ARQ, we use Selective Repeat ARQ
    To utilize more bandwidth
  • 21. COMPARISON CHART
  • 22. THANK YOU