During what phase does the server send a SYN/ACK packet?

During the connection establishment phase, the server sends a SYN/ACK packet as part of the TCP three-way handshake process. This phase begins when a client wants to establish a connection with a server. The client sends a SYN packet to the server to initiate the connection. In response, the server acknowledges this request by sending a SYN/ACK packet back to the client, indicating that it has received the SYN packet and is willing to establish the connection. The final step in this process occurs when the client responds with an ACK packet, completing the handshake and establishing the connection.

This ordering is crucial for reliable data transfer, which TCP aims to achieve. The SYN/ACK is integral in ensuring both parties are synchronized and ready to communicate, which is not applicable during the other listed phases, such as connection termination, data transfer, or connection rejection, where other types of packets and protocols are utilized.