H3C S7500E Series Operation Manual page 699

Operation Manual – Multicast
H3C S7500E Series Ethernet Switches
The multicast data addressed to the multicast group G flows through the RP, reaches
the corresponding DR along the established RPT, and finally is delivered to the
receiver.
When a receiver is no longer interested in the multicast data addressed to a multicast
group G, the directly connected DR sends a prune message, which goes hop by hop
along the RPT to the RP. Upon receiving the prune message, the upstream node
deletes its link with this downstream node from the outgoing interface list and checks
whether it itself has receivers for that multicast group. If not, the router continues to
forward the prune message to its upstream router.
V. Multicast source registration
The purpose of multicast source registration is to inform the RP about the existence of
the multicast source.
Source
Server
Figure 5-6 Multicast registration
As shown in
1) When the multicast source S sends the first multicast packet to a multicast group
G, the DR directly connected with the multicast source, upon receiving the
multicast packet, encapsulates the packet in a PIM register message, and sends
the message to the corresponding RP by unicast.
2) When the RP receives the register message, it extracts the multicast packet from
the register message and forwards the multicast packet down the RPT, and sends
an (S, G) join message hop by hop toward the multicast source. Thus, the routers
along the path from the RP to the multicast source constitute an SPT branch. Each
router on this branch generates an (S, G) entry in its forwarding table. The
multicast source is the root, while the RP is the leaf, of the SPT.
DR RP
SPT
Join message
Register message
Multicast packets
Figure 5-6, the multicast source registers with the RP as follows:
5-10
Chapter 5 PIM Configuration
Host A
Receiver
Host B
Receiver
Host C