Establishing a TCP Connection

In addition, TCP uses segments to determine whether the receiving host is ready to receive the data. When the sending TCP wants to establish connections, it sends a segment called a SYN to the peer TCP protocol running on the receiving host. The receiving TCP returns a segment called an ACK to acknowledge the successful receipt of the segment. The sending TCP sends another ACK segment, then proceeds to send the data. This exchange of control information is referred to as a three-way handshake.