Why Control IP Multicast?
A quick review of IP multicast may help: • IP multicast packets are sent to Class D multicast addresses, in the 224.0.0.0 – 239.255.255.255 range. These destination addresses are referred to as multicast groups. • Receivers join a group to indicate interest in receiving traffic destined to that group. Routers then conspire to get traffic from sources to receivers. A newer approach called Source Specific Multicast (SSM) has receivers indicate which destination group and which source they wish to receive. • When getting started, a source just starts transmitting. The adjacent router(s) determine whether forwarding is needed or not. • When doing Protocol Independent Multicast (PIM) Sparse Mode, the source traffic is registered with the Rendezvous Point (RP), which is used to connect sources and receivers up. Receiver-adjacent routers then trigger creation of a source-specific tree for multicast propagation and replication. The RP is not needed when doing SSM. IP multicast (IPmc) is still