H3C S3600 Series User Manual

Operation Manual – Multicast
H3C S3600 Series Ethernet Switches-Release 1510 Chapter 7 PIM Configuration
7-8
Only one BSR can be elected in a network or management domain, while multiple
candidate BSRs (C-BSRs) can be configured. In this case, once the BSR fails, other
C-BSRs can elect a new BSR through auto-election. Thus, service interruption is
avoided.
In the same way, multiple C-RPs can be configured in a PIM-SM domain, and the RP
corresponding to each multicast group is worked out through the BSR mechanism.
IV. RPT building
Assume the receiver hosts are User B, User D, and User E. When a receiver host joins
a multicast group G, it sends IGMP packets to inform the leaf router directly connected
to the host. Thus, the leaf router acquires the receiver information of the multicast
group G, and then the leaf router sends Join messages to the upper-layer nodes in the
direction of RP, as shown in
Figure 7-5:
RP
Server
Multicast
User A
User B
User C
User D
User E
Join
Join
Join
Source
Receiver
Receiver
Receiver
packets
Join
RPT
Figure 7-5 Diagram for RPT building in PIM-SM
Each router on the path from the leaf router to RP generate (*, G) entries in the
forwarding table. The routers on the path form 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 reaches 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 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 deletes
the links with the downstream routers from the interface list and check whether it has
any receiver interested in the multicast information. If not, the upstream router
continues to forward the Prune message to upstream routers.

H3C S3600 Series Specifications

General

Brand	H3C
Model	S3600 Series
Category	Switch
Language	English