FLOW CONTROL
Flow control is the process of managing the rate at which data is transmitted. Using flow control, a computer receiving data can signal that it is not ready to receive data. TCP provides a flow control mechanism using acknowlegements of TCP sequence numbers.
TCP Sliding Window Mechanism
All segments of data transmitted via TCP are assigned sequence numbers when they are inserted into the TCP packet. When the receiving computer sends an acknowledgement, the acknowledgement will include the next sequence number it is ready to receive.