What is Multicast?

The original intention of the multicast technology is to send information to a target group in the form of "best effort" in the IP network. This target group is called a multicast group. This way, when an active host sends information requests to multiple target hosts, The source host sends only one copy of data, and the destination address of the data is the multicast group address. In this way, all members belonging to the group can receive a copy of the data sent by the original host. In this multicast mode, only the real Members who need the information will receive the information and other hosts will not.

Generally, in traditional network communication, there are two ways, one is a "one-to-one" communication method between the source host and the target host, that is, unicast, and the second is a source host. Communication with all other hosts in the network, i.e. broadcast. Then, if the information needs to be sent from the source host to multiple target hosts in the network, either the broadcast method is used so that all hosts in the network will receive the information, or the unicast method is used by the source host to each different target host. send Message.

It is often used by some groups on the public Internet

Multicast protocols are divided into group membership protocols between hosts and routers and multicast routing protocols between routers and routers. ^[4]

There are many unresolved problems in current multicast technology, such as: multicast security, multicast congestion control, multicast state aggregation, multicast traffic accounting, no congestion control, data packet duplication, out-of-order delivery of data packets, etc. .