Patent ID: 8695050

Claim:
A delivery server for multicasting content via at least one upper router and a plurality of lower routers, comprising: a master storage memory configured to store an identifier of 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; a processor programmed to retrieve play history information from a client device, select related content, related to content played by the client device, based on the retrieved play history information, and optimize the identifier and the session information of content stored on the client device using the identifier and the session information of the related content stored on the master storage memory, and deliver each content to the client device, wherein the session information includes information related to a multicast address of the content, the at least one upper router includes a router processor configured to determine a frequency of occurrence of the multicast address within a book scheduling period based on the information related to the multicast address retrieved from the client device, and a priority order of the multicast address by prioritizing the multicast address which occurs the most.