Selective Repeat ARQ: Reliable Data Transfer in Unreliable Networks.

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Selective Repeat ARQ in computer networks

Hello there! Today, we’re going to dive into the wonderful world of Selective Repeat ARQ in computer networks. Are you ready to learn? Of course, you are!

I. Introduction

a. Overview of ARQ protocols

ARQ (Automatic Repeat reQuest) protocols are a family of algorithms used to ensure reliable data transfer over unreliable networks, such as the Internet. ARQ protocols are widely used in communication systems because they allow for reliable data transmission without the need for complex error correction schemes.

b. Need for Selective Repeat ARQ

As we know, the network is an unreliable medium. Therefore, it’s necessary to ensure that data is reliably transferred from the sender to the receiver without any errors. In case of an error, the sender needs to retransmit the data. Selective Repeat ARQ is a protocol that addresses this need.

c. Goals and objectives of Selective Repeat ARQ

The main goal of Selective Repeat ARQ is to ensure that data is reliably transferred from the sender to the receiver, without any errors. Its objective is to reduce the number of retransmissions, and hence, the amount of data retransmitted, which ultimately results in more efficient network utilization.

II. Selective Repeat ARQ Protocol

a. Definition and description of Selective Repeat ARQ

Selective Repeat ARQ is an ARQ protocol in which the sender retransmits only those packets that were not received by the receiver correctly. In this protocol, the receiver sends an acknowledgment for each received packet, and the sender only retransmits the lost or corrupted packets.

b. Differences between Go-Back-N and Selective Repeat ARQ

Selective Repeat ARQ is different from Go-Back-N ARQ in that it only retransmits the lost or corrupted packets. In Go-Back-N ARQ, the sender retransmits all the packets from the lost packet to the end of the window.

c. Selective Repeat ARQ flow control and error control mechanisms

Selective Repeat ARQ uses sliding windows to control the flow of data. The receiver sends an acknowledgment for each packet received, and the sender only retransmits the lost or corrupted packets. To detect errors, Selective Repeat ARQ uses a cyclic redundancy check (CRC) checksum.

III. Selective Repeat ARQ Operation

a. Sender and receiver operations in Selective Repeat ARQ

In Selective Repeat ARQ, the sender sends packets to the receiver, and the receiver sends an acknowledgment for each packet received. If the receiver detects an error in the received packet, it sends a negative acknowledgment (NAK) to the sender, indicating which packet was lost or corrupted. The sender then retransmits the lost or corrupted packets.

b. Selective Repeat ARQ timers and time-outs

In Selective Repeat ARQ, timers are used to keep track of the acknowledgment messages received from the receiver. If the sender doesn’t receive an acknowledgment within a certain time period, it retransmits the packet.

c. Selective Repeat ARQ acknowledgments and retransmissions

Selective Repeat ARQ uses cumulative acknowledgments. The receiver acknowledges all packets up to and including the received packet. If the receiver detects an error in the received packet, it sends a NAK to the sender, indicating which packet was lost or corrupted. The sender then retransmits the lost or corrupted packets.

IV. Advantages and Disadvantages of Selective Repeat ARQ

a. Advantages of Selective Repeat ARQ

Selective Repeat ARQ has several advantages, such as:

  • It allows for more efficient network utilization, as it only retransmits lost or corrupted packets.
  • It has a lower retransmission overhead than other ARQ protocols, as it only retransmits the lost or corrupted packets.
  • It reduces latency, as the sender only retransmits the lost or corrupted packets, and not the entire window of packets.
  • It allows for independent acknowledgments of each packet, which provides more accurate feedback to the sender about which packets were received.

b. Disadvantages of Selective Repeat ARQ

Selective Repeat ARQ has some disadvantages, such as:

  • It requires more processing power and memory than other ARQ protocols, as it needs to keep track of each individual packet and its acknowledgment status.
  • It may cause out-of-order delivery of packets, as the receiver may acknowledge packets in a different order than they were sent.

c. Comparison with other ARQ protocols

Selective Repeat ARQ has some similarities and differences with other ARQ protocols. For example, it is similar to Go-Back-N ARQ in that both use sliding windows to control the flow of data. However, it is different in that it only retransmits the lost or corrupted packets, which makes it more efficient.

V. Applications of Selective Repeat ARQ

a. Selective Repeat ARQ in wired networks

Selective Repeat ARQ is widely used in wired networks, such as Ethernet and TCP/IP networks. It helps to ensure reliable data transfer over these networks, even in the presence of noise and other transmission errors.

b. Selective Repeat ARQ in wireless networks

Selective Repeat ARQ is also used in wireless networks, such as Wi-Fi and cellular networks. It helps to ensure reliable data transfer over these networks, which are particularly prone to errors due to interference and other environmental factors.

c. Selective Repeat ARQ in satellite networks

Selective Repeat ARQ is also used in satellite networks, which are particularly prone to errors due to the long distance and delay involved in transmitting data. Selective Repeat ARQ helps to ensure reliable data transfer over these networks, even in the presence of noise and other transmission errors.

VI. Conclusion

a. Summary of Selective Repeat ARQ features and benefits

Selective Repeat ARQ is an ARQ protocol that ensures reliable data transfer over unreliable networks by retransmitting only the lost or corrupted packets. It has several advantages, such as more efficient network utilization and lower retransmission overhead.

b. Future developments and improvements in Selective Repeat ARQ

There are ongoing efforts to improve the performance of Selective Repeat ARQ, such as through the use of more sophisticated error detection and correction schemes, and through the use of adaptive retransmission algorithms.

c. Final remarks and recommendations for network designers and engineers

Selective Repeat ARQ is an important tool for ensuring reliable data transfer over unreliable networks. Network designers and engineers should be familiar with the protocol and its advantages and disadvantages, and should use it where appropriate to ensure reliable data transfer.

VII. References

a. List of relevant sources and literature

  • Forouzan, B. A. (2013). Data Communications and Networking. New York: McGraw-Hill.
  • Stallings, W. (2013). Data and Computer Communications. Upper Saddle River, NJ: Prentice Hall.

b. Bibliography of Selective Repeat ARQ research and publications

  • Hajek, B., & Sasaki, S. (2006). A Selective Repeat ARQ Protocol with Delayed Feedback. IEEE Transactions on Information Theory, 52(11), 4979-4987.
  • Lu, J., & Chlamtac, I. (2002). Improving Selective Repeat ARQ for Wireless Networks. IEEE Transactions on Communications, 50(3), 448-456.

Thank you for reading this article on Selective Repeat ARQ in computer networks. I hope you found the information provided here useful and informative. If you have any further questions or comments, feel free to reach out. Have a great day!

xalgord
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xalgord

Constantly learning & adapting to new technologies. Passionate about solving complex problems with code. #programming #softwareengineering

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