7 Difference Between Go-Back-N Protocol And Selective Repeat Protocol

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Go-Back-N Protocol And Selective Repeat Protocol

 Go-Back-N protocol also referred to as Go-Back-N Automatic Repeat reQuest, is a data link layer protocol that uses a sliding window method for reliable and sequential delivery of data frames. It is a case of sliding window protocol having to send window size of N and receiving window size of 1. Normally, in Go-Back-N protocol, the maximum number of frames that can be sent depends upon the size of the sending window. If the acknowledgment of a frame is not is not received within an agreed upon time period, all frames starting from that frame are retransmitted.

Selective Repeat Protocol also referred to as Selective Repeat ARQ (Automatic Repeat reQuest), is a data link layer protocol that uses sliding window method for reliable delivery of data frames. In this protocol, only the erroneous or lost frames are retransmitted, while the good frames are received and buffered.

Selective Repeat Protocol uses two windows of equal size that is; a receiving window that stores the frames received by the receiver and a sending window that stores the frames to be sent. The size is usually half the maximum sequence number of the frame. Usually, the maximum number of frames that can be sent depends upon the size of the sending window.

Key Difference

  1. Selective repeat protocol retransmits only that frame that is damaged or corrupted.  On the contrary, Go-Back-N protocol retransmits only those frames which are damaged or corrupted.
  2. In the Go-back-N protocol, there is need for the sorting of frames that are on the receiver side to maintain the proper sequence of frames.  On the other hand, in the repeat protocol, there is absolutely no need for sorting the sender or the receiver side.
  3. In the Go-Back-N protocol, the receiver stores the frames that are received after encountering the damaged frame in a buffer, till the damaged frame is resent by the sender. On the other hand, in selective repeat protocol, the receiver does not store any frame that is received after encountering the damaged frame, till the damaged frame is retransmitted.
  4. In Go-Back-N protocol, there is relatively less wastage of the bandwidth when compared to the selective repeat protocol in retransmission of frames. In selective repeat protocol, there is a lot of wastage in regard to the bandwidth, in case there is a high error rate in the transmission.  
  5.  Go-Back-N protocol has a sliding window of size less than or equal to (N+1)/2 whereas selective repeat protocol has a sliding window of N-1.
  6. In selective repeat protocol, the type of acknowledgement is individual whereas in Go-Back-N protocol, the type of acknowledgement is cumulative.
  7. The Go-Back-N protocol is slightly more complicated because it comprises of logics, strategies and other functions which are not present in all protocol.

Also Read: Difference Between Pure ALOHA And Slotted ALOHA

Go-Back-N Protocol Vs. Selective Repeat Protocol In Tabular Form

BASIS OF DIFFERENCE   GO-BACK-N PROTOCOL SELECTIVE REPEAT PROTOCOL
Retransmission Go-Back-N protocol retransmits only those frames which are damaged or corrupted. Selective repeat protocol retransmits only that frame that is damaged or corrupted. 
Need For Sorting In the Go-back-N protocol, there is need for the sorting of frames that are on the receiver side to maintain the proper sequence of frames.  In the repeat protocol, there is absolutely no need for sorting the sender or the receiver side.  
Storage Of Frames In the Go-Back-N protocol, the receiver stores the frames that are received after encountering the damaged frame in a buffer, till the damaged frame is resent by the sender. In selective repeat protocol, the receiver does not store any frame that is received after encountering the damaged frame, till the damaged frame is retransmitted.  
Bandwidth Wastage In Go-Back-N protocol, there is relatively less wastage of the bandwidth when compared to the selective repeat protocol in retransmission of frames. In selective repeat protocol, there is a lot of wastage in regard to the bandwidth, in case there is a high error rate in the transmission.   
Sliding Window Size Go-Back-N protocol has a sliding window of size less than or equal to (N+1)/2.   Selective repeat protocol has a sliding window of N-1.  
Type of Acknowledgement In Go-Back-N protocol, the type of acknowledgement is cumulative.   In selective repeat protocol, the type of acknowledgement is individual.  
Complexity The Go-Back-N protocol is slightly more complicated because it comprises of logics, strategies and other functions which are not present in all protocol.   The selective repeat protocol is not complicated in any way.

Also Read: Difference Between Connection-Oriented And Connection-less Services In Telecommunication