A multicast group consists of a group of receivers that require the same data stream. A multicast group uses an IP multicast address identifier. A host that joins a multicast group becomes a member of the group and can identify and receive IP packets that have the IP multicast address as the destination address.
A multicast source sends IP packets that carry multicast destination addresses.
A multicast source can simultaneously send data to multiple multicast groups.
Multiple multicast sources can simultaneously send data to a same multicast group.
A member of a multicast group is a host that requires IP packets from the multicast group. Hosts can choose to join or leave a multicast group, so the members of a multicast group are dynamic. The members can be located anywhere on a network.
A multicast source is generally not a receiver or a member of a multicast group.
A router that supports the multicast feature is called a multicast router.
A multicast router implements the following functions:
Manages group members on the leaf segment networks that connect to users.
Routes and forwards multicast packets.
A multicast distribution tree (MDT) is a tree-shaped packet distribution path along which multicast traffic is sent to multicast receivers.