Routers send Join/Prune messages to join a
branch or prune off a branch from the multicast distribution tree.
A single message contains a join listas well as a prune list. Join
messages are sent by: DRs (near receivers) to RPs indicating
an interest in receiving multicast traffic via RPT. DRs to source when triggering SPT switchovers. RPs to source when triggering SPT switchovers.
Prune
messages are sent by PIM devices to upstream devices to stop forwarding
multicast traffic to the network segment in which the PIM device resides. |