Pim-Dm/Dvmrp - Hirschmann MACH 4000 User Manual

Multicast Routing

9.3 PIM-DM/DVMRP

PIM-DM (Protocol Independent Multicast - Dense Mode) is a routing protocol
that uses the available Unicast routing table of other protocols to steer Multi-
cast data streams.
This ability, and the fast convergence it enables, is the reason why PIM-DM
is now very widely-used.
The DVMRP (Distance Vector Multicast Routing Protocol) is a routing
protocol that uses its own distance vector algorithm to create its own Multi-
cast routing table. DVMRP works similarly to RIP and is limited to 32 hops.
In the past, DVMRP was very widely-used, and today it is used because of
its compatibility with existing applications.
Both protocols use what is known as the Implicit Join method, which means
that a participant who has left the Multicast data stream is not included in
the data flow. To enable a participant who has left to receive Multicase data
streams again, the routers transmit to all participants again after the hold
time has elapsed. For DVMRP, the hold time is fixed at 2 hours. For PIM-DM,
the variable hold time is set at 210 seconds. PIM-DM requires that you set
the hold time to the same value for all the participating routers.
DVMRP
Knows the topology better because
DVMRP uses its own protocol.
Table 14: Advantages of the protocols
Routing L3P
Release 4.0 11/07
PIM-DM
Fast convergence
Optimization through changeable timers
9.3 PIM-DM/DVMRP
103