The present invention relates to broadcasting services by use of Internet Protocol (IP), and IP broadcasting system technology for performing combined services of broadcasting and telecommunications by use of multicast technology.
Multicast communication is technology for transmitting IP datagrams to members belonging to a multicast group while copying it by a multicast router, and is already developed in a wide range of applications. So-called multicast technology complies with standard documents RFC (Request for Comments) 1112, 2236, and 3376 that are produced by the IETF (Internet Engineering Task Force) and publicized by the IAB (Internet Architecture Board), and is a technology for managing and reporting information about members within a group that perform multicast communications. This technology is called IGMP (Internet Group Management Protocol) in the above-described RFC, and is applied to multicast routers. The multicast communications are performed by multicast routers to which the technology is applied. Also, MLD (Multicast Listener Discovery) complying with RFC 2710, 3810 is used. This is applied to multicast communications compliant with IPv6.
Multicast communications are characterized in that only one multicast IP datagram may be transmitted during transmission. Specifically, multicast IP datagrams are automatically copied by multicast routers to which IGMP has been applied, and transmitted to a network to which members of a multicast group belong. A multicast IP datagram is identified by one address value called a multicast address.
Recently, in the IPTV (Internet Protocol TV) broadcasting services, the multicast technology is applied. In the broadcasting services, multicast addresses are allocated to IPTV broadcasting channels for distribution to a multicast group over a network composed of multicast routers. On the other hand, IP broadcasting terminals, which are viewers of the IPTV broadcasting channels, when wanting to receive IPTV broadcasting, can receive the IPTV broadcasting by joining the multicast group to become members of the multicast group. The IP broadcasting terminals must previously know IP information such as multicast address information. Management and notification of such information about multicast members are performed by IGMP and MLD.
These multicast technologies are used for services needing reduced data amounts on a network when a large number of users receive the same data like IPTV broadcasting services. They are also used for IP packet distribution that need a reduced load relating to setting individual transmission destination IP addresses in services that suffer variations in the number of receiving users.
In actual IPTV broadcasting services, however, IP broadcasting users select IPTV broadcasting channels to be viewed from IPTV broadcasting channel names and channel numbers offered by broadcasters. Accordingly, the IP broadcasting terminals must locate a multicast address from the channel numbers to acquire IP broadcasting data from the network. However, when the number of IP broadcast programs offered, the number of IP broadcasting channels, and the number of IP broadcasting terminals themselves due to an increase in the number of users increase, the IP broadcasting system has great difficulties in managing and acquiring all multicast addresses on the network.
On the other hand, in Japanese Patent Application Laid-Open Publication No. 2006-174453, a method is disclosed which, when providing broadcasting digital services, generates correction EPG (Electronic Program Guide) information including IP information specific to broadcasting channels for EPG information including information about contents and kinds of programs, and multiplexes it into broadcasting streams for transmission to user terminals.