The biggest difference between TCP and User Datagram Protocol (UDP), which is its close cousin on the same layer, is that it transmits data in an ordered and reliable fashion. The fact that the operation guarantees delivery is often referred to TCP as a connection-oriented protocol. It does this by first establishing a three-way handshake to synchronize the sequence number between the transmitter and the receiver, SYN, SYN-ACK, and ACK.
The acknowledgment is used to keep track of subsequent segments in the conversation. Finally, at the end of the conversation, one side will send a FIN message, and the other side will ACK the FIN message as well as sending a FIN message of its own. The FIN initiator will then ...
