4.3.6 Flow Control (2/2)
nIf an ACK packet
comes back with a receiver window size
of “0”, that means that the
destination wants the source to hold off with
transmission. In this case the sending host
can only send segments with 1 byte of data.
This is to keep the connection alive between the two ends, i.e., keep
ACKs flowing from destination to
source indicating the window size.