Patent ID: 7882531

Claim:
A multicasting system comprising: a delivery server for multicasting a content via at least one upper router and a plurality of lower routers, a plurality of client devices for playing the content multicast by the delivery server, an upper router controller for controlling the upper router and a lower router controller for controlling the plurality of lower routers, the client device including: a play history storage unit for storing play history information of the content in each client device, an individual storage unit for storing an identifier of at least part of the contents to be multicast by the delivery server and session information related to multicasting of the content with the identifier mapped to the session information, a content retrieving unit for retrieving the content from the delivery server in accordance with the identifier and the session information of the content stored on the individual storage unit, and a content playing unit for playing the retrieved content; the delivery server including: a master storage unit for storing an identifier of a content as a delivery target and session information relating to multicasting of the content as the delivery target with the identifier mapped to the session information, an optimizer for retrieving the play history information from the play history storage unit in the client device, selecting a related content related to the content played by the client device based on the retrieved play history information, and optimizing the identifier and the session information of the content stored on the individual storage unit using the identifier and the session information of the related content stored on the master storage unit, and a content delivery unit for delivering each content to the client device; the upper router controller including: a session information retrieving unit for retrieving from each client device the session information of a related content planned to be multicast within a book scheduling period stored on the individual storage unit, from the session information of the related contents stored on the individual storage unit, a book scheduling unit for determining a priority order of multicast addresses within the book scheduling period in accordance with the retrieved session information and scheduling, based on the determined priority order and a permitted workload of an access network connecting the upper router to the lower router, the multicast addresses in which each lower router participates within the book scheduling period, and a schedule information notifier for notifying each client device of book scheduling information indicating scheduling results of the book scheduling unit; and the lower router controller controlling participation and disengagement to the multicast address of each lower router within the book scheduling period based on the book scheduling information.