TCP three-way handshake
termnetworking
The three-message exchange that opens a TCP connection: SYN, SYN-ACK, ACK.
Before any data flows, both sides synchronize sequence numbers in three steps, agreeing they can hear each other. It is the polite handshake underneath every web page and file transfer, and its half-open state is what a SYN flood abuses.
Also known as: 3-way handshake, syn syn-ack ack, tcp handshake