Ip Multicast; Fig. 9.1 Igmp Snooping In The L2 Network - SMC Networks 7824M/VSW - annexe 1 Manual

CLI

9 IP Multicast

348
IP communication provides three types of packet transmission: unicast, broadcast and
multicast. Unicast is the communication for a single source host to a single destination
host. This is still the most common transmission form in the IP network. Broadcast is the
communication for a single source host to all destination hosts on a network segment.
This transmission is also widely used especially by network protocols, but it sometimes
may not be efficient for those hosts in the subnet who are not participating in the broad-
cast. Multicast is the communication for a single or many source hosts to a specific group
of destination hosts, which is interested in the information from the sources. This type of
packet transmission can be deployed for a number of applications with more efficient utili-
zation of the network infrastructure.
The point of implementing multicast is how to deliver source traffic to specific destinations
without any burden on the sources or receivers using the minimized network bandwidth.
The solution is to create a group of hosts with addressing the group, and to let the net-
work determine how to replicate the source traffic to the receivers. The traffic will then be
addressed to the multicast address and replicated to the multiple receivers by network
devices. Standard multicast protocols such as IGMP provide most of these capabilities.
IP multicast features on the switch consist of the group membership management, Layer
2 multicast forwarding, which allows network administrators to successfully achieve the
effective and flexible multicast deployment.
Fig. 9.1 shows an example of the IP multicast network. In this case, the switch is config-
ured only with IGMP snooping (L2 multicast forwarding feature) in the Layer 2 network.
Layer 2 Network
Set-top Box
Set-top Box
Fig. 9.1 IGMP Snooping in the L2 network
IGMP Join/Leave PIM Join/Prune
message message
VDSL DSLAM
IGMP Snooping
PIM-SM
Management Guide
TigerAccess™ EE
Layer 3 Network
Multicast data
SMC7824M/VSW
Multicast Server