Why in TCP's Go-Back-N Algorithm window size(N) has to be smaller than the sequence number space(S): S>N? I tried figuring it out myself but don't quiet get it
Assume that sequence space was four (sequence numbers 0,1,2,3). Lets say window size was also 4. Sender sends 4 packets with sequence numbers (0,1,2,3). Receiver receives all four packets. So it sends 4 acknowledgements(0,1,2,3). Now assume all acknowledgements are lost. Sender will resend all four packets but receiver will assume they're the new ones. To avoid confusions arising from lost acknowledgements, we keep n < s
来源：https://stackoverflow.com/questions/28444055/go-back-n-window-size