Which event is always triggered when a client initially connects to a virtual server configured with an HTTP profile.

HTTP_DATA triggers when the BIG-IP receives HTTP payload data, which occurs after the connection is accepted and HTTP processing has begun.

CLIENT_DATA triggers when any data is received from the client, which happens after CLIENT_ACCEPTED and might not always involve a complete HTTP request.

HTTP_REQUEST triggers only when the BIG-IP receives a complete HTTP request, which requires an established connection and the client sending application-layer data.

The CLIENT_ACCEPTED event is foundational to iRules and fires immediately when the BIG-IP successfully accepts a new client-side TCP connection, prior to any application-layer processing, including HTTP. This event signifies the establishment of the network connection, making it the first point of iRule execution for any new client connection.