Multicast and IGMP
Multicast is a developed version of broadcast, where broadcast sends out packets to all members on the network. This happens on a specific range of IP address, much like tuning in to a specific TV channel. This happens in the real world by all of the multicast devices telling the router which multicast IP addresses it wishes to listen to. Now that the router has this information in the router table it only sends the relevant data to the receiver.
IGMP (Internet Group Management Protocol) is an addition to the multicast principle, this is the rule set that sets up the routing table in the router and only sends out the relevant messages to the receiver. The router periodically asks on the network if there are any new subscribers and to what information they wish to listen to.
Neets uses Multicast in our control systems, amplifiers and switching relays which incorporates LAN control. We use multicast for detecting the LAN devices that your control system is combined with in the project.