H3C S5500-EI Series Operation Manual page 18

Operation Manual – Multicast
H3C S5500-EI Series Ethernet Switches
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.
In the ASM model, multicast routes come in intra-domain routes and inter-domain
routes.
An intra-domain multicast routing protocol is used to discover multicast sources
and build multicast distribution trees within an AS so as to deliver multicast data to
receivers. Among a variety of mature intra-domain multicast routing protocols,
protocol independent multicast (PIM) is a popular one. Based on the forwarding
mechanism, PIM comes in two modes – 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 delivery of multicast
information between two ASs. So far, mature solutions include multicast source
discovery protocol (MSDP).
For the SSM model, multicast routes are not divided into inter-domain routes and
intra-domain routes. Since receivers know the position of the multicast source,
channels established through PIM-SM are sufficient for multicast information transport.
II. Layer 2 multicast protocols
Layer 2 multicast protocols include IGMP Snooping/MLD Snooping and multicast
VLAN/IPv6 multicast VLAN.
network.
Source
Receiver
Figure 1-8 Position of Layer 2 multicast protocols
Figure 1-8
Multicast VLAN
/IPv6 Multicast VLAN
IGMP Snooping
/MLD Snooping
Receiver
IPv4/IPv6 multicast packets
shows where these protocols are in the
1-12
Chapter 1 Multicast Overview