HP MSR1002-4 Configuration Manual page 18

Layer 3 multicast protocols—IGMP, MLD, PIM, IPv6 PIM, and MSDP.
Layer 2 multicast refers to IP multicast operating at the data link layer.
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Layer 2 multicast protocols—IGMP snooping and MLD snooping.
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IPv4 and IPv6 multicast protocols:
For IPv4 networks—IGMP snooping, IGMP, PIM, and MSDP.
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For IPv6 networks—MLD snooping, MLD, and IPv6 PIM.
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This section provides only general descriptions about applications and functions of the Layer 2 and
Layer 3 multicast protocols in a network. For more information about these protocols, see the related
chapters.
Layer 3 multicast protocols
In Figure 8, Layer 3 multicast protocols include multicast group management protocols and multicast
routing protocols.
Figure 8 Positions of Layer 3 multicast protocols
Receiver
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Multicast group management protocols:
Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) protocol
are multicast group management protocols. Typically, they run between hosts and Layer 3
multicast devices that directly connect to the hosts to establish and maintain multicast group
memberships.
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Multicast routing protocols:
A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain
multicast routes and correctly and efficiently forward multicast packets. Multicast routes
constitute loop-free data transmission paths (also known as multicast distribution trees) from a
data source to multiple receivers.
In the ASM model, multicast routes include intra-domain routes and inter-domain routes.
An intra-domain multicast routing protocol discovers multicast sources and builds multicast
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distribution trees within an AS to deliver multicast data to receivers. Among a variety of
mature intra-domain multicast routing protocols, PIM is most widely used. Based on the
forwarding mechanism, PIM has dense mode (often referred to as PIM-DM) and sparse
mode (often referred to as PIM-SM).
An inter-domain multicast routing protocol is used for delivering multicast information

between two ASs. So far, mature solutions include Multicast Source Discovery Protocol
(MSDP) and MBGP. MSDP propagates multicast source information among different ASs.
AS 1
IGMP/MLD
PIM/IPv6 PIM
Source
Receiver
MSDP
Receiver
9
AS 2
IGMP/MLD
PIM/IPv6 PIM
IGMP/MLD