Dell POWEREDGE M1000E - Manual (Page 1156)

1156 Managing IPv4 and IPv6 Multicast
Only one RP address can be used at a time within a PIM domain. You can
configure a static RP on the switch. However, if the PIM domain uses the BSR
to dynamically learn the RP, configuring a static RP is not required. By default
the RP advertised by the BSR is used, but you can specify that the static RP to
override any dynamically learned RP from the BSR.
If an interface on a switch configured with PIM-SM neighbors another PIM-
SM domain, the PIM BSR messages should not flood into the neighboring
PIM domain because the neighbor domain might not share the same set of
RPs, candidate RPs, BSR, and candidate BSRs. The switch software allows you
to configure an interface that borders the PIM boundary prevent transmission
(sending and receiving) of PIM BSR messages. PIM-SM is defined in RFC
4601.
Using PIM-DM as the Multicast Routing Protocol
Unlike PIM-SM, PIM-DM creates source-based shortest-path distribution
trees that make use of reverse-path forwarding (RPF). PIM-DM assumes that
when a sender starts sending data, all downstream routers and hosts want to
receive a multicast datagram. PIM-DM initially floods multicast traffic
throughout the network. Routers that do not have any downstream neighbors
prune back the unwanted traffic. In addition to PRUNE messages, PIM-DM
makes use of graft and assert messages. Graft messages are used whenever a
new host wants to join the group. Assert messages are used to shutoff
duplicate flows on the same multi-access network.
There are two versions of PIM-DM. Version 2 does not use the IGMP
message; instead, it uses a message that is encapsulated in IP package, with
protocol number 103. In Version 2, a Hello message is introduced in place of a
query message.
PIM-DM is appropriate for:
• Densely distributed receivers
• Few senders-to-many receivers (due to frequent flooding)
• High volume of multicast traffic
• Constant stream of traffic
NOTE: Dell recommends configuring a first-hop router from the multicast video
source as the RP.