Communication System and Terminal Registration Method Thereof, Server Unit, and Terminal Device

A terminal registration method used in a communication system which comprises a plurality of endpoints configured to make telephone communications, and a plurality of server units which receive registration requests from these endpoints in different priority levels, the method comprising:

• assigning, by each of the endpoints, identification information used to discriminate a cause of generation of a registration request to a message of the registration request to the server unit;
• transmitting, by the endpoint, the message assigned with the identification information, to one of the server units;
• specifying, by the server unit, the cause from the identification information assigned to the received message;
• determining, by the server unit, whether or not to permit registration of the endpoint as a source of the received message based on the specified cause and the priority level;
• and
• registering, by the server unit, the endpoint when the registration is permitted, and instructing the endpoint to redirect the message when the registration is not permitted.

A server unit used in a communication system which comprises a plurality of endpoints configured to make telephone communications, and a plurality of server units which receive registration requests from these endpoints in different priority levels, the server unit comprising:

• a specification module configured to specify a cause of generation of a registration request from identification information which is assigned to a message of the registration request and is used to discriminate a cause of generation of the registration request;
• a determination module configured to determine whether or not to permit registration of the endpoint as a source of the received message based on the specified cause and the priority level;
• and
• a registration processor configured to register the endpoint when the determination module permits the registration, and instruct the endpoint to redirect the message when the determination module does not permit the registration.