TCP 플래그 참조

Synchronize — initiates a connection

Connection establishment (3-way handshake step 1&2)

Acknowledgment — acknowledges received data

Acknowledges all segments after initial SYN

Finish — gracefully closes a connection

Connection termination (4-way close)

Reset — abruptly closes a connection

Error recovery, refuse connections, close immediately

Push — push data to application immediately

Real-time applications like SSH, Telnet

Urgent — urgent pointer field is valid

Out-of-band data signaling (rarely used)

ECN-Echo — congestion notification

Explicit Congestion Notification support

Congestion Window Reduced

Tells peer congestion window was reduced