Patent ID: 8918518

Claim:
An IP multimedia subsystem, comprising an access session controller and a network-wide home subscriber server system, wherein the access session controller comprises: a message reception module adapted to receive a call request message and a response message from a user or a call request message and a response message from a network device; a service trigger configuration module adapted to configure trigger information; a session control module adapted to generate a command for transmitting a message triggering a corresponding application server and establish, maintain and release a session upon determining from the trigger information configured by the service trigger configuration module that the call request message or the response message satisfies a condition of triggering the application server, and to generate, during establishment of the session, a command to transmit the call request message directly to an access session controller at the side of a called user or a corresponding breakout gateway control function module; and a message transmission module adapted to transmit the message according to the command from the session control module, wherein the network-wide home subscriber server system is connected with the access session controller and adapted to store network-wide subscriber information and indexes thereof for inquiring by the access session controller, wherein the message reception module is further adapted to receive a registration message from a user, and wherein the access session controller further comprises: a registration control module adapted to interact with the network-wide home subscriber server system according to the registration message to control a registration procedure of the user.