Allied Telesis AT-8550 - Manual (Page 182)

Overview
10-2
Overview
IP multicast routing is a function that allows a single IP host to send a
packet to a group of IP hosts. This group of hosts can include devices
that reside on the local network, within a private network, or outside
of the local network.
IP multicast routing consists of the following functions:
❑ A router that can forward IP multicast packets.
❑ A router-to-router multicast protocol (for example, Distance
Vector Multicast Routing Protocol (DVMRP) or Protocol
Independent Multicast (PIM)).
❑ A method for the IP host to communicate its multicast group
membership to a router (for example, Internet Group
Management Protocol (IGMP)).
Note
You should configured IP unicast routing before you configure IP
multicast routing.
DVMRP
Overview
DVMRP is a distance vector protocol that is used to exchange routing
and multicast information between routers. Like RIP, DVMRP
periodically sends the entire routing table to its neighbors.
DVMRP has a mechanism that allows it to prune and graft multicast
trees to reduce the bandwidth consumed by IP multicast traffic.
PIM-DM
Overview
Protocol Independent Multicast-Dense Mode (PIM-DM) is a multicast
routing protocol that is similar to DVMRP.
PIM-DM routers perform reverse path multicasting (RPM). However,
instead of exchanging its own unicast route tables for the RPM
algorithm, PIM-DM uses the existing unicast route table for the
reverse path. As a result, PIM-DM requires less system memory.
Using PIM-DM, multicast routes are pruned and grafted in the same
way as DVMRP.
Note
You can run either DVMRP or PIM-DM on the switch, but not both
simultaneously.