An IP multimedia subsystem comprising: a serving session control apparatus configured to execute session control of user equipment; and a proxy session control apparatus connected to the serving session control apparatus and located at an interface with an IP access network, wherein the serving session control apparatus includes a terminating call acceptance unit configured to accept a terminating call to the user equipment, and a terminating call relay unit configured to relay terminating call information including an identifier of the user equipment to the proxy session control apparatus in response to acceptance of the terminating call to the user equipment by the terminating call acceptance unit, the proxy session control apparatus includes a terminating call processing unit configured to receive the terminating call information from the serving session control apparatus, a restoration execution unit configured to execute restoration of a subscriber profile linked with the user equipment based on reception of the terminating call information by the terminating call processing unit, and an address holding unit configured to hold an address of a policy-and-charging apparatus included in a response received from a routing agent along with the execution of the restoration by the restoration execution unit, the restoration execution unit being configured to reestablish a session between the user equipment and the policy-and-charging apparatus based on the address of the policy-and-charging apparatus held by the address holding unit, and to cause the user equipment to execute re-registration with the IP multimedia subsystem. a serving session control apparatus configured to execute session control of user equipment; and a proxy session control apparatus connected to the serving session control apparatus and located at an interface with an IP access network, wherein the serving session control apparatus includes a terminating call acceptance unit configured to accept a terminating call to the user equipment, and a terminating call relay unit configured to relay terminating call information including an identifier of the user equipment to the proxy session control apparatus in response to acceptance of the terminating call to the user equipment by the terminating call acceptance unit, the proxy session control apparatus includes a terminating call processing unit configured to receive the terminating call information from the serving session control apparatus, a restoration execution unit configured to execute restoration of a subscriber profile linked with the user equipment based on reception of the terminating call information by the terminating call processing unit, and an address holding unit configured to hold an address of a policy-and-charging apparatus included in a response received from a routing agent along with the execution of the restoration by the restoration execution unit, the restoration execution unit being configured to reestablish a session between the user equipment and the policy-and-charging apparatus based on the address of the policy-and-charging apparatus held by the address holding unit, and to cause the user equipment to execute re-registration with the IP multimedia subsystem. a terminating call acceptance unit configured to accept a terminating call to the user equipment, and a terminating call relay unit configured to relay terminating call information including an identifier of the user equipment to the proxy session control apparatus in response to acceptance of the terminating call to the user equipment by the terminating call acceptance unit, the proxy session control apparatus includes a terminating call processing unit configured to receive the terminating call information from the serving session control apparatus, a restoration execution unit configured to execute restoration of a subscriber profile linked with the user equipment based on reception of the terminating call information by the terminating call processing unit, and an address holding unit configured to hold an address of a policy-and-charging apparatus included in a response received from a routing agent along with the execution of the restoration by the restoration execution unit, a terminating call processing unit configured to receive the terminating call information from the serving session control apparatus, a restoration execution unit configured to execute restoration of a subscriber profile linked with the user equipment based on reception of the terminating call information by the terminating call processing unit, and an address holding unit configured to hold an address of a policy-and-charging apparatus included in a response received from a routing agent along with the execution of the restoration by the restoration execution unit, the restoration execution unit being configured to reestablish a session between the user equipment and the policy-and-charging apparatus based on the address of the policy-and-charging apparatus held by the address holding unit, and to cause the user equipment to execute re-registration with the IP multimedia subsystem.