PPT Slide

Go back n/selective repeat

• go back n :
  • What to do when a frame in the middle of a long stream is bad? Large # of succeeding frames may come to receiver before sender is told of error.
  • On discovering error, a solution is go back n. Here receiver discards all subsequent frames (upto n) & sends no ack for the discarded frames. Therefore the receiver DLL refuses all frames but the next one it must give to the NL.
  • Eventually sender will retransmit all frames including lost/damaged one.

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