The establishment of a TCP connection involves a negotiation called 3 way handshake. What type of message sends the client to the server in order to begin this negotiation?

RST (reset) is used to abruptly terminate an existing connection or reject an invalid connection attempt, not to initiate one.

ACK (acknowledgment) is the final step sent by the client to confirm receipt of the server's SYN-ACK, not the first step to begin the handshake.

SYN-ACK is the server's response to the client's initial SYN, meaning it is sent by the server - not by the client to begin the negotiation.

The client begins the TCP 3-way handshake by sending a SYN packet with the SYN flag set, indicating it wants to establish a connection and sharing its initial sequence number. The server responds with a SYN-ACK, and finally the client sends an ACK to complete the handshake. Only the SYN is sent by the client to initiate - the other messages are either server responses or completions.