Patent ID: 7948946

Claim:
A method for providing a multicast service when a Mobile Node (MN) performs handoff from a first Access Router (AR) to a second AR in a mobile Internet Protocol (IP) communication system including the first AR and second AR, the MN being a source node for providing the multicast service to a number of receivers and currently performing communication with the first AR, the second AR being different from the first AR, the method comprising the steps of: sending a request for information for fast handoff from the MN to the first AR; sending a notification from the first AR to the MN indicating whether the second AR can provide the multicast service in response to the fast handoff information request; sending a notification from the MN to the first AR indicating that the second AR must transmit subsequently-occurring multicast service data, after the MN is notified whether the second AR can provide the multicast service; sending a notification from the first AR to the second AR indicating handoff initiation of the MN when the first AR is notified that the second AR must transmit subsequently-occurring multicast service data; sending a notification from the second AR to the first AR indicating handoff initiation notification acknowledgement, after the second AR is notified of the handoff initiation; sending a notification from the first AR to the receivers indicating that the MN has performed handoff from the first AR to the second AR, when the first AR is notified of the handoff initiation notification acknowledgement so that the receivers are controlled to join a new multicast tree to be provided with the multicast service; sending a notification from the first AR to the receivers indicating that the second AR will transmit the multicast service data to the MN and the second AR, after the first AR notifies the receivers of the handoff of the MN; delivering normal data from the first AR to the second AR after the first AR notifies the second AR that the second AR will transmit the multicast service data, the normal data including reception multicast other than the multicast service data received at the MN as a target; sending a notification from the MN to the second AR indicating that the MN has been disconnected from the first AR and connected to the second AR, after the MN is notified that the second AR will transmit the multicast service data; and forwarding the normal data from the second AR to the MN when the second AR is notified by the MN that the MN has been connected to the second AR.