Huawei Quidway S5600 Series Operation Manual page 467

Operation Manual – Multicast Protocol
Quidway S5600 Series Ethernet Switches-Release 1510
Each router on the path from the leaf router to RP will generate (*, G) entries in the
forwarding table. The routers on the path forms a branch of RPT. A (*, G) entry
represents the information from any source to the multicast group G. RP is the root of
RPT and the receivers are leaves of RPT.
When the packet from the multicast source S to the multicast group G passes by RP,
the packet will reach the leaf router and receiver host along the established path in
RPT.
When the receiver is not interested in the multicast information any more, the multicast
router nearest to the receiver will send Prune messages to RP hop by hop in the
direction reverse to RPT. When the first upstream router receives the Prune message, it
will delete the links with the downstream routers from the interface list and check
whether it has the receivers interested in the multicast information. If not, the upstream
router will continue to forward the Prune message to upstream routers.
V. Multicast source registration
In order to inform RP about the existence of multicast source S, when multicast source
S sends a multicast packet to the multicast group G, the router directly connected to S
will encapsulate the received packet into a registration packet and send it to the
corresponding RP in unicast form, as shown in Figure 7-6:
Source
Server
Figure 7-6 Diagram for SPT building in PIM-SM
When RP receives the registration information from S, it will decapsulate the
registration information and forward the multicast information to the receiver along RPT,
and on the other hand, it will send (S, G) join messages to S hop by hop. The passed
routers constitute a branch of SPT. The multicast source S is the root of SPT and RP is
the destination of RP.
The multicast information sent by the multicast source S will reach RP along the built
SPT, and then RP will forward the multicast information along the built RPT.
RP
Join
Multicast
Join
Register
packets
Join
SPT
Register
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7-9
Chapter 7 PIM Configuration
User A
Receiver
User B
User C
Receiver
User D
Receiver
User E