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Sliding Window Protocol, Go-Back-N ARQ (Automatic Repeat reQuest) Protocol, and Selective Repeat ARQ Protocol are all techniques used for flow control and error control in data communication systems. Here’s an overview of each:

Sliding Window Protocol:

  • Sliding Window Protocol is a flow control technique that allows multiple frames to be transmitted and acknowledged before the sender needs to stop and wait for acknowledgment.
  • It uses a sliding window mechanism to maintain a range of sequence numbers for transmitted frames.
  • The sender can transmit up to a specified number of frames (window size) without waiting for acknowledgment.
  • The receiver acknowledges received frames and informs the sender about the next expected frame.
  • Sliding Window Protocol improves throughput compared to Stop-and-Wait Protocol by allowing pipelining of frames.

Go-Back-N ARQ Protocol:

  • Go-Back-N ARQ is an error control protocol that is based on Sliding Window Protocol.
  • In Go-Back-N ARQ, the sender is allowed to transmit multiple frames without waiting for acknowledgment, similar to Sliding Window Protocol.
  • However, if an error is detected in any frame, the receiver discards all subsequent frames in the window and requests retransmission of all frames starting from the damaged or lost frame (hence the name “Go-Back-N”).
  • The sender then retransmits all frames in the window, even if some of them were already successfully received by the receiver.

Selective Repeat ARQ Protocol:

  • Selective Repeat ARQ is another error control protocol based on Sliding Window Protocol.
  • In Selective Repeat ARQ, the receiver individually acknowledges correctly received frames and buffers out-of-order frames until missing frames are received.
  • If an error is detected in a frame, only that frame is retransmitted by the sender, rather than retransmitting all frames in the window like in Go-Back-N ARQ.
  • Selective Repeat ARQ improves efficiency compared to Go-Back-N ARQ by avoiding unnecessary retransmissions of frames that were successfully received by the receiver.

Summary:

  • Sliding Window Protocol allows multiple frames to be transmitted before waiting for acknowledgment, improving throughput.
  • Go-Back-N ARQ retransmits all frames in the window if an error is detected, which can be inefficient but simple to implement.
  • Selective Repeat ARQ retransmits only the damaged frames, leading to better efficiency but requiring more complex buffering and acknowledgment mechanisms at the receiver.