Multicast technology is one of IP network data transmission. Before introducing IP multicast technology, first we make a simple introduction of unicast, multicast and broadcast:
Multicast transmission: A point-to-point network connection between the sender and each recipient. If a sender sends the same data to multiple recipients at the same time, it must also copy the same number of identical packets accordingly. If a large number of hosts want to get the same copy of the packet, it will cause the sender to pay heavy, long delay, network congestion; to ensure a certain quality of service to increase the hardware and bandwidth.
Broadcast (Broadcast) transmission: refers to the IP subnet broadcast packets, all within the subnet within the host will receive these packets. Broadcast means that the network to the subnet each host to deliver a packet, regardless of whether the host is willing to receive the packet. So the use of broadcast is very small, only in the local subnet effective, through the router and network equipment to control the broadcast transmission.
Multicast transmission: A point-to-multipoint network connection between the sender and each recipient. If a sender sends the same data to multiple recipients at the same time, it is only necessary to copy the same packet.
Multicast solves the problem of low efficiency of unicast and broadcast. When a certain user needs specific information in the network, the multicast source (that is, the multicast information sender) sends only the information. The multicast router establishes the tree route for the multicast packet by means of the multicast routing protocol. The transmitted information It is only possible to copy and distribute at the intersection as far as possible.