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LTP-8X optical line terminal
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Chapter 24.
Multicast Configuration
Introduction
The Chapter describes peculiarities of IPTV service configuration.
Internet Group Management Protocol (IGMP) is used in hosts and routers for multicasting support. It
provides all systems of a physical network with relevant information: which hosts are included in groups
and which group corresponds to a host.
IGMP snooping is a technique that allows network devices of the channel level (switches) to snoop IGMP
requests from hosts to a group router in order to decide whether group traffic transmission to the
corresponding interfaces should be started or stopped. When a switch snoops a host's IGMP request for
connection to a multicast group, it adds the port the host is connected to into the group (for group
traffic retranslation). And vice versa, having snooped a "leave_group" request, the switch removes the
corresponding port from the group.
Fig. 24.1. IGMP Snooping Is Disabled
Fig. 24.1 shows multicasting of IGMP traffic regardless of whether an end host needs the traffic or not.
When IGMP snooping becomes enabled, the multicasting situation changes as follows: the switch will
