H3C S5120-EI Series, Руководство по эксплуатации

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Multicast Protocols
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Generally, we refer to IP multicast working at the network layer as Layer 3 multicast and the
corresponding multicast protocols as Layer 3 multicast protocols, which include IGMP/MLD,
PIM/IPv6 PIM, MSDP, and MBGP/IPv6 MBGP; we refer to IP multicast working at the data link
layer as Layer 2 multicast and the corresponding multicast protocols as Layer 2 multicast protocols,
which include IGMP Snooping/MLD Snooping, and multicast VLAN/IPv6 multicast VLAN.
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IGMP Snooping, IGMP, multicast VLAN, PIM, MSDP, and MBGP are for IPv4, MLD Snooping,
MLD, IPv6 multicast VLAN, IPv6 PIM, and IPv6 MBGP are for IPv6.
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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.
Layer 3 multicast protocols
Layer 3 multicast protocols include multicast group management protocols and multicast routing
protocols.
Figure 1-8 describes where these multicast protocols are in a network.
Figure 1-8
Positions of Layer 3 multicast protocols
1) Multicast management protocols
Typically, the internet group management protocol (IGMP) or multicast listener discovery protocol (MLD)
is used between hosts and Layer 3 multicast devices directly connected with the hosts. These protocols
define the mechanism of establishing and maintaining group memberships between hosts and Layer 3
multicast devices.
2) Multicast routing protocols
A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes
and forward multicast packets correctly and efficiently. Multicast routes constitute a loop-free data
transmission path from a data source to multiple receivers, namely, a multicast distribution tree.