Multicast delivery method, system, and content server
If a failure occurs in a content server having a function to deliver a content as a multicast IP packet, the influence on the end user is minimized. An active content server and a standby content server are provided. The active content server delivers a multicast content, and the standby content server joins a corresponding multicast group, receives the multicast packet sent by the active content server, and monitors the delivery status of the active content server. If no multicast packet is delivered from the active content server before the scheduled end of the content delivery determined by the content delivery end information (content length in time, sequence number, or absolute end time) specified in each content, the standby content server starts the multicast content delivery.
1 . A multicast delivery method for a multicast delivery system,
the multicast delivery system comprising:
an active content server and a standby content server for delivering a multicast packet containing content data; and
a multicast router for receiving the multicast packet delivered by the active content server and the standby content server and transferring the multicast packet to an interface corresponding to a multicast destination address, and
the multicast delivery method comprising the steps of:
the active content server holding content data and content management information that includes content identification information, a multicast content delivery destination address, and delivery end information, and delivering the multicast packet containing multicast management information and the content data through the multicast router;
the standby content server holding the same content management information and content data as the active content server;
the standby content server joining a multicast group of the multicast packet delivered by the active content server through the multicast router, in accordance with the content identification information and the multicast destination address of the multicast management information;
the standby content server receiving the multicast packet delivered by the active content server through the multicast router; and
if an interruption of the multicast packet delivery from the active content server is detected, the standby content server delivering the multicast packet containing the multicast management information and content data not delivered due to the interruption, through the multicast router on behalf of the active content server.
2 . A multicast delivery method according to claim 1 , further comprising the step of the active content server and the standby content server receiving a content delivery start request or a content delivery stop request specifying common content management information and storing the content management information internally.
3 . A multicast delivery method according to claim 1 , wherein the active content server specifies a sequence number of each content data item included in one content or lapse-of-time information indicating the lapse of time since the beginning of content delivery, in the multicast packet, and delivers the multicast packet with the sequence number or the lapse-of-time information added.
4 . A multicast delivery method according to claim 3 , wherein the standby content server detects an interruption of content delivery from the active content server by detecting the nonarrival of the multicast packet delivered by the active content server;
if an interruption of content delivery is detected, the standby content server determines the interruption point where the content delivery is interrupted, in accordance with the sequence number or the lapse-of-time information in the multicast packet received earlier; and
the standby content server resumes multicast packet delivery from the interruption point.
5 . A multicast delivery method according to claim 1 , wherein the standby content server does not send but discards created multicast packet while the active content server is normally delivering the content.
6 . A multicast delivery method according to claim 5 , wherein the standby content server switches the packet discard processing to the packet transmission processing if an interruption of multicast delivery from the active content server is detected while the multicast packet is being discarded.
7 . A multicast delivery system comprising:
an active content server and a standby content server for delivering a multicast packet containing content data; and
a multicast router for receiving the multicast packet delivered by the active content server and the standby content server and transferring the multicast packet to an interface corresponding to a multicast destination address,
wherein the active content server holds content data and content management information that includes content identification information, a multicast content delivery destination address, and delivery end information, and delivers the multicast packet containing multicast management information and the content data through the multicast router;
the standby content server holds the same content management information and content data as the active content server;
the standby content server joins a multicast group of the multicast packet delivered by the active content server through the multicast router, in accordance with the content identification information and the multicast destination address of the multicast management information;
the standby content server receives the multicast packet delivered by the active content server through the multicast router; and
if an interruption of the multicast packet delivery from the active content server is detected, the standby content server delivers the multicast packet containing the multicast management information and content data not delivered due to the interruption, through the multicast router on behalf of the active content server.
8 . A multicast delivery system according to claim 7 , further comprising a controller for giving a content delivery start instruction or a content delivery stop instruction to the active content server and the standby content server, with common content management information specified.
9 . A content server for delivering a multicast packet containing content data through a multicast router for transferring the multicast packet to an interface corresponding to a multicast destination address;
the content server, when acting as an active content server, holding content data and content management information that includes content identification information, a multicast content delivery destination address, and delivery end information, and delivering the multicast packet containing the content data and multicast management information through the multicast router;
the content server, when acting as a standby content server, holding the same content data and content management information as the active content server;
the standby content server joining a multicast group of the multicast packet delivered by the active content server through the multicast router, in accordance with the content identification information and the multicast destination address of the multicast management information;
the standby content server receiving the multicast packet delivered by the active content server through the multicast router; and
if an interruption of the multicast packet delivery from the active content server is detected, the standby content server delivering the multicast packet containing the multicast management information and content data not delivered due to the interruption, through the multicast router on behalf of the active content server.
10 . A content server according to claim 9 , the content server receiving a content delivery start request or a content delivery stop request with common content management information specified and storing the content management information internally, when acting as the active content server or the standby content server.