GO BACK N PROTOCOL

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describing the selective repeat and go back n protocol.

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GO BACK N PROTOCOL

  1. 1. Go Back – n & Selective RepeatProtocol<br />
  2. 2. Go-Back-N protocol<br />Concept<br />Introduce a window of size n<br />Can inject n packets on net before hearing an ACK<br />Each packet is labeled with a sequence number.<br />
  3. 3. ADVANTAGES OF GO-BACK N<br />The sender can send many frames at a time.<br /> Timer can be set for a group of frames. <br />One ACK can acknowledge more than one frames. <br /> Efficiency is more. <br />
  4. 4. DISADVANTAGES <br />Buffer requirement.<br />Transmitter needs to store the last N packets.<br />Scheme is inefficient when delay is large and data transmission rate is high.<br /> Unnecessary Retransmission of many error-free packets.<br />
  5. 5. Selective Repeat Protocol<br />Go-Back-N inefficient because multiple frames are resent when errors or losses occur.<br />SR protocol retransmits only an individual frame containing the error.<br />Buffer is provided in this case.<br />
  6. 6. FramesHandling<br />1<br />2<br />3<br />4<br />5<br />6<br />7<br />8<br />9<br />10<br />1<br />2<br />3<br />E<br />5<br />6<br />7<br />8<br />9<br />10<br />Sending window<br />Receiving window contains the error in 4th frame.<br />
  7. 7. in Go back n protocol….<br />Sending window<br />1<br />2<br />3<br />4<br />5<br />6<br />7<br />8<br />9<br />10<br />4<br />5<br />6<br />7<br />8<br />9<br />10<br />Receiving window<br />1<br />2<br />3<br />E<br />5<br />6<br />7<br />8<br />9<br />10<br />Frames are discarded.<br />Retransmitting the discarded frames.<br />
  8. 8. in Selective repeat protocol….<br />Sending window<br />1<br />2<br />3<br />4<br />5<br />6<br />7<br />8<br />9<br />10<br />4<br />Getting remaining frames from the buffer.<br />Retransmitting frame.<br />Receiving window<br />1<br />2<br />3<br />E<br />5<br />6<br />7<br />8<br />9<br />10<br />Output Buffer<br />Error in 4th Frame<br />5<br />9<br />7<br />Reordering the frames.<br />8<br />
  9. 9. COMPARISON CHART<br />
  10. 10. THANK YOU !!!<br />

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