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Figure 1-45. PIM-DM Interface Configuration
The Protocol Independent Multicast – Dense Mode (PIM-
DM) protocol should be used in networks with a low delay
(low latency) and high bandwidth as PIM-DM is optimized to
guarantee delivery of multicast packets, not to reduce
overhead.
The PIM-DM multicast routing protocol is assumes that all
downstream routers want to receive multicast messages and
relies upon explicit prune messages from downstream
routers to remove branches from the multicast delivery tree
that do not contain multicast group members.
PIM-DM has no explicit 'join' messages. It relies upon
periodic flooding of multicast messages to all interfaces and
then either waiting for a timer to expire (the Join/Prune
Interval) or for the downstream routers to transmit explicit
'prune' messages indicating that there are no multicast
members on their respective branches. PIM-DM then
removes these branches ('prunes' them) from the multicast
delivery tree.
Because a member of a pruned branch of a multicast
delivery tree may want to join a multicast delivery group (at
some point in the future), the protocol periodically removes
the 'prune' information from its database and floods multicast
messages to all interfaces on that branch. The interval for
removing 'prune' information is the Join/Prune Interval.
62 VH-2402-L3 Management Guide
9033691-01
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