Quanta Cloud Technology QuantaMesh QNOS5, Configuration Manual

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PIM-SM uses a Bootstrap Router (BSR), which advertises information to other multicast routers about the RP.
In a given network, a set of routers can be administratively enabled as candidate bootstrap routers. If it is
not apparent which router should be the BSR, the candidates flood the domain with advertisements. The
router with the highest priority is elected. If all the priorities are equal, then the candidate with the highest
IP address becomes the BSR.
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.
8.1.10.2. 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
To minimize the repeated flooding of datagrams and subsequent pruning associated with a particular
source- group (S,G) pair, PIM-DM uses a State Refresh message. This message is sent by the router(s)
directly connected to the source and is propagated throughout the network. When received by a router on
its RPF interface, the State Refresh message causes an existing prune state to be refreshed. State Refresh
messages are generated periodically by the router directly attached to the source.
8.2. Default L3 Multicast Values
IP and IPv6 multicast is disabled by default. Table 23 shows the default values for L3 multicast and the
multicast protocols.