Selective repeat protocol

In previous article we studied about sliding window protocol.

1. Selective repeat protocol is based on sliding window protocol.
2. It is also called Selective Repeat ARQ (Automatic Repeat reQuest).
3. Here, only the erroneous or lost frames are re-transmitted.
4. Here, window size of sender and receiver are equal.
5. Window size is half of maximum sequence number.
6. If maximum sequence numbers are 8.
7. Than sender having window size of 4 and receiver having window size of 4.
8. Window size is greater than one else it will become stop and wait.
9. Sender transmit multiple frames to the receiver.
10. Number of frames transmitted depends on window size.
11. Now sender wait for the acknowledgement.
12. Receiver stores valid frames in receivers window.
13. It sends the sequence numbers of the erroneous and missing frame to the sender along with acknowledgement.
14. Sender re-transmits the frames whose sequence number is given by the acknowledgements. 
15. Sender then continues sending the other frames.