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C
HAPTER
7: M
ULTICAST
P
ROTOCOL
and the BSR (Bootstrap Router) to advertise multicast information to all PIM-SM
routers, and uses the join/prune information of the router to build the RP-rooted
shared tree (RPT). This reduces the bandwidth occupied by data packets and
control packets, and reduces the processing overhead on the router.
Multicast data flows along the shared tree to the network segments that have
multicast group members. When the data traffic is sufficient, the multicast data
flow can switch over to the SPT (Shortest Path Tree) rooted on the source to
reduce network delay. PIM-SM does not depend on the specified unicast routing
protocol but uses the present unicast routing table to perform the RPF check.
When running PIM-SM the user needs to configure candidate RPs and BSRs. The
BSR is responsible for collecting the information from the candidate RP and
advertising the information.
PIM-SM Operating
Principle
The working procedures for PIM-SM include: neighbor discovery, building the
RP-rooted shared tree (RPT), multicast source registration and switch over to the
SPT.
Neighbor Discovery
The PIM-SM router uses Hello messages to perform neighbor discovery when it is
started. All network nodes running PIM-SM stay in touch with one another by
periodically sending Hello messages.
Build the RP Shared Tree (RPT)
When hosts join a multicast group G, the leaf routers that directly connect with
the hosts send IGMP messages to learn the receivers of multicast group G. In this
way, the leaf routers calculate the corresponding rendezvous point (RP) for
multicast group G and then send join messages to the node of a higher level
toward the rendezvous point (RP). Each router along the path between the leaf
routers and the RP will generate (*, G) entries in the forwarding table, indicating
that all packets sent to multicast group G are applicable to the entries no matter
from which source they are sent. When the RP receives the packets sent to
multicast group G, the packets will be sent to leaf routers along the path built and
then reach the hosts. In this way, an RP-rooted tree (RPT) is built as shown in
Figure 45
.
Summary of Contents for SuperStack 4
Page 6: ...18 ABOUT THIS GUIDE ...
Page 34: ...46 CHAPTER 1 GETTING STARTED ...
Page 62: ...74 CHAPTER 3 VLAN OPERATION ...
Page 69: ...PoE Configuration 81 ...
Page 70: ...82 CHAPTER 4 POWER OVER ETHERNET POE CONFIGURATION ...
Page 98: ...110 CHAPTER 5 NETWORK PROTOCOL OPERATION ...
Page 220: ...232 CHAPTER 8 ACL CONFIGURATION ...
Page 408: ...420 CHAPTER B RADIUS SERVER AND RADIUS CLIENT SETUP ...
Page 432: ...444 APPENDIX D 3COM XRN ...