@pyrate31 OK lets get some terminology defined.
Unicast := 1 image to 1 computer == 1 data stream. If you want deploy 1 image to 20 computers that will be 20 data streams.
Multicast := 1 image to n computers == 1 data stream. If you want to deploy 1 image to 20 computers that only consumes 1 data stream in bandwidth.
Data stream := the transfer of the image from the fog server to the target computer.
20 unicast data streams will consume 20 times the bandwidth and system resources of a multicast stream.
Multicast imaging is harder to setup because it relies on your network infrastructure to be setup to support multicast messages. If you have a single subnet then multicasting will work without much hassle. If you are trying to multicast between subnets (fog server on subnet A and clients on subnet B) your subnet router will need to support multicast messages.