Flow control is the process of regulating the amount of data sent by a host to another host on the network. The flow control mechanism controls packet flow so that a sender does not transmit more packets than a receiver can process. TCP uses a sliding window flow control protocol. In each TCP segment, the receiver specifies in the receive window field the amount of additional received data (in bytes) that it is willing to buffer for the connection. The sending host can send only up to that amount of data before it must wait for an acknowledgment and window update from the receiving host. Answer option A is incorrect. TCP uses a sequence number for identifying each byte of data. Answer option B is incorrect. TCP timestamp helps TCP to compute the round-trip time between the sender and receiver. Answer option C is incorrect. Congestion control concerns controlling traffic entry into a telecommunications network, so as to avoid congestive collapse by attempting to avoid oversubscription of any of the processing or link capabilities of the intermediate nodes and networks and taking resource reducing steps, such as reducing the rate of sending packets. It should not be confused with flow control, which prevents the sender from overwhelming the receiver.