Chapter 14
IPv6 PIM-SM Configuration
Table of Contents
14.1 PIM-SM Overview
PIM-SM Introduction
PIM-SM is mainly used in the following situations:
l
Group members sparsely locate in a relatively large scale.
l
The network bandwidth resources are limited.
PIM-SM does not depend on a specific unicast routing protocol. PIM-SM assumes that
all routers on a shared segment do not need to send multicast packets. The routers only
can receive and send multicast packets after they request to join a multicast group on
their own initiative. PIM-SM advertises the multicast information to all routers supporting
PIM-SM through an RP. In PIM-SM, a router joins or leaves the multicast group explicitly.
This reduces the number of packets and the bandwidth used by the control packets.
RP
PIM-SM sends multicast packets by using a shared tree. A shared tree has a center point
that is responsible for sending packets to all the source-sending ends in the multicast
group. Each source-sending end sends packets to the center point along the shortest
path, and then takes the center point as the root point to distribute the packets to various
receiving ends of the group.
The group center point of the PIM-SM is called the RP. There may be several RPs in a
network, but there is only one RP in a multicast group.
A router can obtain the location of the RP in two ways.
1.
Configure the RP manually and statically on the routers running PIM-SM.
2.
PIM-SMv2 obtains the location through the candidate RP advertisement.
The
candidate RP with the highest priority becomes a formal RP.
In PIM-SM, some routers running PIM-SM are manually set to work as candidate Bootstrap
Router (
). The candidate BSR with the highest priority is elected as the formal BSR.
The BSR is responsible for collecting the candidate RP information on the multicast routers
in group to find out candidate RPs in the multicast domain. It notifies the candidate RPs to
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