Scope
This article explains the basics of multicast on switches.
What is multicast?
In an Axia AoIP system, audio is (normally) sent out "to the masses" instead of to one, individual receiver. Doing this reduces the load on devices, as they do not have to manage each audio stream to each device that wants that audio. Instead, using multicast, the audio is sent out as a single stream (or "group") for devices to "subscribe" to. This allows other devices to "tune in" to the stream instead of request it directly from the sending device.
Example: A good analogy would be a radio vs. a telephone. I can choose to talk to someone one-on-one by calling them directly on my phone,
but if I'm trying to talk to 100 people at once, I'd need 100 connections to my phone. That could be a problem.
Instead, I might choose to use a radio to address them to reduce the load on my phone. Furthermore, multicast only sends to those devices that wish to receive it, so in order to hear me talking on the radio, someone would have to "tune in" to get my signal.
Multicast works a little different than the radio example above. Since the devices themselves are not communicating one-on-one with
Devices will first send a request, or "query", to receive a specific multicast stream.
While this method is fantastic for reducing the load on a device, it can add considerable load to the switch, as the switch is managing which devices subscribe and unsubscribe to/from the multicast stream.
This is a "Callout" that can be put into places to make known important information
IGMP: What does it do?
IGMP is the abbreviation for "Internet Group Management Protocol." In short, it is what switches use to manage multicast streams.
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