Moxa Technologies EDS-508 user manual Multicast Filtering, Network without multicast filtering

EDS-508 Series User’s Manual Featured Functions

publisher/subscriber communications models by multicasting packets that could flood a network with heavy traffic. IGMP Snooping provides the ability to prune multicast traffic so that it travels only to those end destinations that require the traffic, thus reducing the amount of traffic on the Ethernet LAN.

Multicast Filtering

Multicast filtering is the process that ensures that end-stations only receive multicast traffic if they register to join specific multicast groups. With multicast filtering, network devices only forward multicast traffic to the ports that are connected to registered end-stations. The following figure shows how a network behaves without multicast filtering, and with multicast filtering.

The Network without multicast filtering

Group 1 Multicast Stream Group 2 Multicast Stream

IGMP Group 2 IGMP Group 1 IGMP Group 2 IGMP Group 1

All end-stations must handle the traffic whether they need it or not.

The Network with multicast filtering

Group 1 Multicast Stream Group 2 Multicast Stream

IGMP Group 2 IGMP Group 1 IGMP Group 2 IGMP Group 1

End-stations only receive dedicated traffic belonging to the same group.

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