Terminal and multicast address distribution server

A multicast address distribution server comprising:

• processing circuitry configured to
• receive an assignment request from a terminal for requesting assignment of a multicast address;
• hold correspondence relationship between attribute information of the terminal and a multicast address;
• decide, based on the attribute information of the terminal as received from the terminal, a multicast address to be distributed to the terminal;
• notify the terminal about the decided multicast address;
• and
• when a change in the attribute information of the terminal is detected at the terminal, receive a second assignment request including the attribute information after the change, and assign a new multicast address to the terminal according to the change in the attribute information,
• wherein
• the attribute information of the terminal contains installation area information about geographical area of a fixed installation of the terminal, and
• when a change in the geographical area of fixed installation of the terminal is detected, the processing circuitry receives the second assignment request.

A multicast group changing method for changing a multicast group in which a terminal participates, the multicast group changing method comprising:

• sending, to a multicast address distribution server, an assignment request including attribute information of the terminal, so as to request assignment of a multicast address enabling identification of a terminal group;
• setting, in response to the assignment of the multicast address, the multicast address in the terminal and making the terminal to participate in the terminal group corresponding to the multicast address;
• and
• reissuing, when a change in the attribute information of the terminal is detected, a second assignment request including the attribute information after the change, so as to request the multicast address distribution server for a new multicast address and change a terminal group for participation according to change in the attribute information,
• wherein
• the attribute information of the terminal contains installation area information about geographical area of a fixed installation of the terminal, and
• when a change in the geographical area of fixed installation of the terminal is detected, the terminal performs the reissuing of the second assignment request.