3.4 now points forwards to 4.4.1; 4.4.1 carries the text

   Finally, after any necessary messaging association setup has
   completed, a Confirm MUST be sent if the Response requested it.  Once
   the Confirm has been sent, the Querying node assumes that routing
   state has been installed at the responder, and can send normal Data
   messages for the flow in question; recovery from a lost Confirm is
   discussed in Section 5.3.3.