Alcatel 060320-10, Rev. B Configuration Manual page 212

PIM Overview
Once the Sender's DR receives the (S,G) Join message, the DR sends the multicast packets natively along
the Shortest Path Tree. At this point, Router X (the router shown between the Sender's DR and the
Receiver's DR) will be receiving two copies of the multicast data—one from the SPT and one from the
RPT. This router drops the packets arriving via the RP tree and forwards only those packets arriving via
the SPT.
An (S, G, RPT) Prune message is sent toward the RP. As a result, traffic destined for this group from this
particular source will no longer be forwarded along the RPT. The RP will still receive traffic from the
Source. If there are no other routers wishing to receive data from the source, the RP will send an
(S, G) Prune message toward the source to stop this unrequested traffic.
page 6-16
Sender
DR
Sender
DR
OmniSwitch AOS Release 7 Advanced Routing Configuration Guide
Traffic is received on this router
from both the SPT and RPT.
Router X
RP
Receiver
Legend
Multicast Traffic
(S, G, RPT) Prune
Router X
(S, G, RPT)
Prune Message
RP
Receiver
Configuring PIM
DR
SPT switchover is enabled at the
last hop DR; the switchover is
initiated upon receiving the first
multicast data packet.
DR
March 2011