Multicast technology is designed in the IP network, in the form of a “best” to send information to a particular target group, the target group is called a multicast group. When active host send information demand to the target host, the source host just send a copy of the data, the data of the destination address is a multicast group address.In this way, all belong to the group members can receive a copy of the original host data, the multicast mode members who really need information will receive information,while others can’t receive it.Therefore, multicast method solves the duplication of data and bandwidth in unicast, and also solves the waste of bandwidth in multicast method.