The Best Guide to Understanding the Working and Implementation of Selective Repeat ARQ

With the increase in the exchange of information and data between network channels, the need to govern the exchange of information is very important, where the “Selective Repeat ARQ” protocol, which uses the buffer application to handle the transmission of data

In this article on “what is selective repeat ARQ?”, we will look into the working and definitions of the protocol in a network channel.

What is Selective Repeat ARQ Protocol? 

  • The working method is based on the sliding window protocol, is a part of the data link layer, and uses a buffer at the receiver and sender sides.
  • The term ARQ in the protocol refers to the Automatic Repeat Request and sends the next frame for each acknowledged frame.

After looking into the protocol, let’s move on to learn some important features of the protocol.

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Important Features of the Protocol

To better understand the functioning of the selective repeat ARQ protocol, let’s take a look at some of the important attributes for the same, which are:                    

  • The N, in this protocol, remains the same for the sender and the receiver side, i.e., the Sender window’s N = Receiver window’s N.            
  • If the sender does not receive the acknowledgment for a frame within a certain time, that frame is retransmitted without influencing other frames.     
  • This protocol also shares a NACK (Negative Acknowledgement) for either lost or damaged frames for that frame to be retransmitted.

Continuing, let’s apply the definition of the protocol to understand the working steps of the protocol.

Working of the Protocol

The selective repeat ARQ protocol applies the sliding window protocol for functioning as its principle and integrates the buffer method to retransmit damaged data frames.

Let’s take a look at the steps involved in working of the protocol:  

  1. To initiate the transmission, the sender side will share the data frames simultaneously with the receiver side, according to the window size assigned.
  2. After the receiver side receives the frames, it will use the first frame and send the acknowledgment to the sender side.
  3. With the acknowledgment received by the sender side for the first frame, the receiver side will receive the next frame.
  4. During the exchange of frames, the sender side might not receive the acknowledgment for a specified frame due to network error.
  5. In such a situation, the receiver side will share the acknowledgment for the next frame, and the sender will retransmit the damaged data frame to the receiver side.

Let’s move on to some advantages and disadvantages of applying the Selective Repeat ARQ protocol in the network.

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Advantages of the Protocol

Applying the selective repeat arq protocol provides multiple advantages to the network model, which are:

  • The protocol applies the buffer method, so memory is needed on the sender and receiver sides.
  • It retransmits only the data frames damaged during transmission in the network channel.
  • Need less retransmission, which increases the efficiency and uses moderate bandwidth requirements.

With the end of this part, we are completed with our article on ‘Selective Repeat ARQ Protocol.’

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In this article on ‘Selective repeat ARQ Protocol’, we learned about the importance of applying the network's data exchange protocol and its working procedure to deepen our knowledge on the topic further.

If you want to learn more about the protocol and topics related to network protocols, you can refer to Simplilearn’s Cyber Security Expert course. After completing this specifically designed professional course, you’ll become familiar with the terms used in the network protocols and their working in a communication channel.

Do you have any questions about this article on ‘Selective Repeat ARQ Protocol’. If yes, feel free to mention them in the comment section at the bottom of this page. Our expert team will help you solve your queries at the earliest.

About the Author

Anmol KapoorAnmol Kapoor

Anmol is a Research Analyst who aims to become a Data Scientist one day. He enjoys Data Management systems and analysis. You will find him reading a book when he is not working.

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