What Is Selective Repeat ARQ and How Does It Work?

TL;DR

Selective Repeat ARQ is a sliding window protocol that enhances efficiency by only retransmitting lost or corrupted frames instead of the entire window. The receiver buffers correct frames and sends negative acknowledgments for missing ones, resulting in fewer overall retransmissions compared to Go-Back-N ARQ.

Transcript

hello everyone welcome back to the next lecture in the computer network series and today we will see the selective-repeat AI q let's start the session with the outcomes in today's session we have only one outcome upon the completion of this session the learner will be able to understand the working of selective-repeat ER q let's see the working pri... Read More

Key Insights

• 😚 Selective-repeat ARQ is a sliding window protocol that focuses on retransmitting only lost or erroneous frames.
• 👣 The receiver keeps track of sequence numbers and sends negative acknowledgments for missing or damaged frames.
• 😘 Selective-repeat ARQ is more efficient than go-back-N ARQ due to its lower number of retransmissions.
• 🪟 The window size does not significantly affect the working of selective-repeat ARQ.
• 😚 Buffered frames in selective-repeat ARQ are not retransmitted unless they are lost or erroneous.
• 😚 In go-back-N ARQ, all frames in the current window are retransmitted if a single frame is lost or the acknowledgement is lost.
• 💁 Selective-repeat ARQ requires the sender and receiver to maintain sequence number information.

Questions & Answers

Q: How does selective-repeat ARQ differ from go-back-N ARQ?

In selective-repeat ARQ, only lost or erroneous frames are retransmitted, while correct frames are received and buffered. In go-back-N ARQ, all frames in the current window are retransmitted if a single frame is lost or the acknowledgement is lost.

Q: What does the receiver do when a frame is missing or damaged in selective-repeat ARQ?

The receiver sends a negative acknowledgment for the missing or damaged frame. The sender then retransmits only that specific frame, rather than retransmitting the entire current window of frames.

Q: Is the window size significant in selective-repeat ARQ?

The window size does not play a significant role in selective-repeat ARQ. The sender retransmits frames based on negative acknowledgments received, regardless of the window size.

Q: How does selective-repeat ARQ compare to go-back-N ARQ in terms of efficiency?

Selective-repeat ARQ is more efficient than go-back-N ARQ as it retransmits only the frames for which negative acknowledgments are received. This results in a lower number of retransmissions.

Key Insights:

• Selective-repeat ARQ is a sliding window protocol that focuses on retransmitting only lost or erroneous frames.
• The receiver keeps track of sequence numbers and sends negative acknowledgments for missing or damaged frames.
• Selective-repeat ARQ is more efficient than go-back-N ARQ due to its lower number of retransmissions.
• The window size does not significantly affect the working of selective-repeat ARQ.
• Buffered frames in selective-repeat ARQ are not retransmitted unless they are lost or erroneous.
• In go-back-N ARQ, all frames in the current window are retransmitted if a single frame is lost or the acknowledgement is lost.
• Selective-repeat ARQ requires the sender and receiver to maintain sequence number information.
• The efficiency of selective-repeat ARQ makes it a preferred choice over go-back-N ARQ in certain scenarios.

Summary & Key Takeaways

• Selective-repeat ARQ is a sliding window protocol that only retransmits lost or erroneous frames, while correct frames are received and buffered.

• The receiver keeps track of sequence numbers and sends negative acknowledgments for missing or damaged frames.

• In selective-repeat ARQ, the number of retransmissions is lower than in go-back-N ARQ, making it more efficient.