Difference between Stop and Wait, GoBackN and Selective Repeat protocols

Stop and Wait protocol

Stop and Wait protocol is a protocol for flow control mechanism. In this protocol, sender sends one frame at a time and waits for acknowledgment from the receiver. Once acknowledged, sender sends another frame to the receiver. If acknowledgment is not received then frame/packet is retransmitted.

GoBackN protocol

GoBackN is also a protocol for flow control mechanism. In this protocol, sender sends n frames at a time and wait for commulative acknowledgment. If acknowledgment is not received then entire frames are retransmitted again.

Selective Repeat protocol

Selective Repeat is also a protocol for flow control mechanism. In this protocol, sender sends n frames at a time and wait for acknowledgment of packets received in particular order. If acknowledgment is not received then lost packets are transmitted again which is based on receiver acknowledgment. Receiver maintains a buffer of lost packets.

Following are some of the important differences between Stop and Wait protocol and Sliding Window protocol.

Sr. No.	Key	Stop and Wait protocol	GoBackN protocol	Selective Repeat protocol
1	Sender window size	In Stop and Wait protocol, Sender window size is 1.	In GoBackN protocol, Sender window size is N.	In Selective Repeat protocol, Sender window size is N.
2	Receiver Window size	In Stop and Wait protocol, Receiver window size is 1.	In GoBackN protocol, Receiver window size is 1.	In Selective Repeat protocol, Receiver window size is N.
3	Minimum Sequence Number	In Stop and Wait protocol, Minimum Sequence Number is 2.	In GoBackN protocol, Minimum Sequence Number is N+1 where N is number of packets sent.	In Selective Repeat protocol, Minimum Sequence Number is 2N where N is number of packets sent.
4	Efficiency	In Stop and Wait protocol, Efficiency formular is 1/(1+2*a) where a is ratio of propagation delay vs transmission delay.	In GoBackN protocol, Efficiency formular is N/(1+2*a) where a is ratio of propagation delay vs transmission delay and N is number of packets sent.	In Selective Repeat protocol, Efficiency formular is N/(1+2*a) where a is ratio of propagation delay vs transmission delay and N is number of packets sent.
5	Acknowledgement Type	In Stop and Wait protocol, Acknowledgement type is individual.	In GoBackN protocol, Acknowledgement type is cumulative.	In Selective Repeat protocol, Acknowledgement type is individual.
6	Supported Order	In Stop and Wait protocol, no specific order is needed at receiver end.	In GoBackN protocol, in-order delivery only are accepted at receiver end.	In Selective Repeat protocol, out-of-order deliveries also can be accepted at receiver end.
7	Retransmissions	In Stop and Wait protocol, in case of packet drop,number of retransmition is 1.	In GoBackN protocol, in case of packet drop,numbers of retransmitions are N.	In Selective Repeat protocol, in case of packet drop,number of retransmition is 1.

Mahesh Parahar

Published on 15-Apr-2020 07:09:00

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