What is essential for TCP connections during the connection establishment phase?

The essential process for establishing TCP connections is the Three-Way-Handshake. This procedure is fundamental to TCP because it ensures that both the client and server are ready to communicate and that they acknowledge each other’s presence before data transmission begins.

The first step involves the client sending a synchronization (SYN) packet to the server, indicating that it wants to establish a connection. In the second step, the server responds with a SYN-ACK packet, acknowledging the client's request while also expressing its willingness to connect. Finally, the client sends an acknowledgment (ACK) back to the server, confirming that the connection has been established successfully. This sequence of messages not only facilitates a reliable and ordered data transfer but also helps in negotiating parameters such as the initial sequence numbers.

This process is vital because it sets up the connection parameters and establishes both endpoints’ readiness to exchange data. Consequently, without the Three-Way-Handshake, a reliable and efficient data transfer cannot be ensured in TCP communications.