Which event is always triggered when a client initially connects to a virtual server configured...

The BIG-IP processing flow follows a specific sequence of events as a packet moves through the system.

TCP Handshake: Before any application-layer data (like HTTP) can be processed, a TCP connection must be established.

The First Event: The very first event triggered when a client completes the 3-way handshake with the virtual server is CLIENT_ACCEPTED.

Profile Influence: Even if an HTTP profile is attached, the system must first "accept" the connection at the protocol level. HTTP_REQUEST only triggers after the client sends data that the BIG-IP recognizes as a valid HTTP request. If a client connects but never sends a request, CLIENT_ACCEPTED will have fired, but HTTP_REQUEST will not.