In my lecture notes, the example of go back n shows that when reciever recieved a packet number n, reciever will send a ACK number n to the sender.
But when i search on the web, some of the website said that reciever will send the n+1 ACK to the sender in order to request next packet.
Which one is the correct one about go back n?
For Go-Back-N, the receiver uses cumulative acknowledgment, which sends the sequence number of largest correctly received in order packet. Two example to help you understand. 1. The receiver has correctly received packet n and sent ACK=n. Later the receiver received packet n+1, then it will send ACK=n+1. 2. The receiver has correctly received packet n and sent ACK=n. Later the receiver received packet n+2, then it will send ACK=n.
Now, what you have searched on the web is talking about TCP not Go-Back-N. For TCP, ACK is different from Go-Back-N. Although TCP still uses cumulative acknowledgment, but acknowledgment number is the sequence number of the next byte the receiver is expecting from the sender, i.e., n+1.
