To do multicast well on a large scale, you have to have higher end managed switches and know how to configure them appropriately, which takes more I.T. chops than many people possess, possibly even requiring working with a serial terminal. That said, properly configured switches with multicast data can potentially handle that large scale scenario's bandwidth substantially better than unicast if there are multiple receivers listening for the same universe of data.
For further investigation if you're interested, the folks at Axia have learned and published a lot on this topic as it relates to their LiveWire IP-Audio technology. They use standard Ethernet as transport for all audio sources, destinations, and mixing consoles in complex multi-studio radio and broadcast facilities. Their devices constantly stream 48Khz/24-bit uncompressed audio onto the network as a multicast stream per source, with potentially thousands of sources on a single network that can be subscribed to, routed, and received anywhere in the facility, all through standard managed ethernet switches -- all with an input to output latency of less than 3ms. It's impressive stuff and some of their white papers that are on their site may shed some insights on working with multicast for E1.31 as well. They, for example, require managed switches, and recommend only Cisco switches due to improper or incomplete multicast implementations in other brands.
Brian
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