There's an error in the first chapter "Connecting two hosts" concerning the go-back-n cumulative acknowledgements part. Here's the sentence (error in bold) :
" Consider for example a go-back-n receiver that received frames 1, 2 and 3. It sent OK1, OK2 and OK3. Unfortunately, OK1 and OK2 were lost. Thanks to the cumulative acknowledgements, when the receiver receives OK3, it knows that all three frames have been correctly received. "
There's an error in the first chapter "Connecting two hosts" concerning the go-back-n cumulative acknowledgements part. Here's the sentence (error in bold) :
" Consider for example a go-back-n receiver that received frames 1, 2 and 3. It sent OK1, OK2 and OK3. Unfortunately, OK1 and OK2 were lost. Thanks to the cumulative acknowledgements, when the receiver receives OK3, it knows that all three frames have been correctly received. "
This is the sender that receives the ack.