H3C S5600 Series Operation Manual page 464

Operation Manual – Multicast
H3C S5600 Series Ethernet Switches
I. Layer 3 multicast protocols
Layer 3 multicast protocols include multicast group management protocols and
multicast routing protocols.
a network.
Receiver
Figure 1-5 Positions of Layer 3 multicast protocols
1) Multicast management protocols
Typically, the Internet Group Management Protocol (IGMP) 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.
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 autonomous system (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).
Figure 1-5 describes where these multicast protocols are in
AS 1
IGMP
PIM
Source
1-11
Chapter 1 Multicast Overview
Receiver
MSDP
Receiver
AS 2
IGMP
PIM
IGMP