A communication system includes a probe transmission server 3 which transmits at fixed intervals of time a probe multicast packet distributed along the same path as a main multicast packet, a delay insertion server 5 which appends the same fixed delay time to each of the main multicast packet and the probe multicast packet, a backup server 2 which generates synchronism and delay backup multicast packets from the main multicast packet and transmits them, and a communication control device 7 which determines the communication of the main multicast packet based on a reception interval of the probe multicast packet, generates a backup main multicast packet from the backup multicast packet when a communication break is detected, and transmits it. The communication system, upon implementing a broadcast-type multicast service, enhances compensation of communication breaks when detecting and recovering from a fault in an IP network, and reduces the network traffic.