- URG - Process the current TCP packet immediately. Directs the receiving system to examine the “urgent pointer” field.
- ACK - Acknowledgement. Directs the receiving system to examine the “acknowledgement number” field.
- PSH - Push. Elevate the priority of the packet’s data, but does not otherwise change rules around packet processing.
- RST - Reset. Terminates the connection forcefully.
- SYN - Synchronize. Used during the initial three-way handshake to set a shared (starting) sequence number.
- FIN - Finish. Indicates that the connection may be dropped gracefully.