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DES-7200 Configuration Guide Chapter 7 PIM-SMv6
Configuration
7-1
7 PIM-SMv6
Configuration
7.1 PIM-SM Overview
PIM (Protocol Independent Multicast) is designed by IDMR (Inter-domain
Multicast Routing) working group. As its name implied, PIM does not depend on a
specific unicast routing protocol. It utilizes the unicast routing table established by
various unicast routing protocols to enable the RPF check function instead of
maintaining a separate multicast routing table for forwarding multicast packets.
Compared with other multicast protocols, PIM overhead falls down at large extent
for PIM does not need to receive and send multicast route update. The concept
behind PIM design is that support and flexible transformation between SPT and
the shared tree is enabled for higher multicast efficiency. There are two kinds of
PIM modes-dense mode and sparse mode.
PIM-SM (Protocol Independent Multicast Sparse Mode) is a multicast routing
protocol in sparse mode. In the PIM-SM domain, the device running PIM-SM
sends the Hello message at a specific interval to discover adjacent devices
running PIM-SM and be in charge of DR election. Here DR sends the “join/prune”
message to its direct group members in the direction of the root node of the
multicast distribution tree or sends the data from the direct multicast source to the
multicast distribution tree.
Figure 5 PIM-SM explicit join/prune mechanism