This TCP flag instructs the sending system to transmit all buffered data immediately.

SYN (Synchronize) is used to initiate a TCP three-way handshake and establish a connection, not to manage data buffering.

RST (Reset) abruptly terminates a TCP connection due to an error or unexpected condition, unrelated to data buffering.

The PSH flag in a TCP segment signals both the sending TCP stack to transmit all buffered data without waiting and the receiving TCP stack to pass the data immediately to the application layer. This is used in interactive protocols like Telnet where low-latency delivery of small data chunks is required, bypassing the normal buffering that TCP uses to improve efficiency.

URG (Urgent) marks specific data in the segment as urgent and instructs the receiver to process it out of band ahead of normal data, not to flush all buffered data.

FIN (Finish) is used to gracefully close a TCP connection after all data has been sent, not to push buffered data.