# Invoking a call diversion (Q.SIG)

In the NMS ISDN Q.SIG implementation, the application at the originating node is responsible for attempting to reroute a call if it is requested to do so by the served user node's application. When the originating node offers a call to the served user node, the served user application requests the diversion by sending an acu_ss_divert_invoke extended data structure to the stack in an ACU request message.