Suppose there are 0,1,2,3 packets in Sender window(win size =4). As both sender and receiver has same window size, out of order delivery of packets are allowed. If suppose 0,1,2,3 are sent and 0 is lost and 1,2,3 are accepted. Then after re-transmission complete window will slide by N for new data or when 0 is re-transmitted other 3 slots will be filled with new data?
packet 0 is lost and and all the three packets(1,2,3) is accepted . at the time when packet 0 is not received by the receiver ,receiver send the negative acknowledgement of packet 0 i.e. NAK 0 .after this NAK 0 is received by sender and it send the packet 0 again and then sender window slide by N for new data.
lets suppose if next packet are 4,5,6,7,8,9…
and next window contain 4,5,6,7 packets