In some cultures, when two persons meet, they often greet each other by shaking hands. The act of shaking hands is understood by both parties as a signal for a friendly greeting. Connections on the network are similar. The first handshake requests synchronization. The second handshake acknowledges the initial synchronization request and synchronizes the connection parameters in the opposite direction. The third handshake segment is an acknowledgement used to inform the destination that both sides agree that a connection has been established. When two hosts communicate using TCP, a connection is established before data can be exchanged. After the communication is completed, the sessions are closed and the connection is terminated. The connection and session mechanisms enable TCP’s reliability function. Hosts track each data segment within a session and exchange information about what data is received using the information in the TCP header. TCP is a full-duplex protocol, where each connection represents two one-way communication streams, or sessions. To establish the connection, the hosts perform a three-way handshake. Control bits in the TCP header indicate the progress and status of the connection.