Multicast versus Unicast

[Fan Liu 1]

From V18 Rockwell introduced unicast mode for Ethernet/IP communication. But unicast mode seems not effective compared to multicast transmission even with taffic contorl ability. For the same data produced by controller will send multiple times to each consumer due to the point to point transmission mode. Enable IGMP protocol within managed switch will effectively limit the multicast traffic on Ethernet/IP communication. So which is the best practice for Ethernet/IP, apply default multicast transmission with IGMP enabled managed swith for traffic control or just configure both producer & consumer to work on unicast mode? Edited 9 Aug 2012 by Fan Liu

[Ken Roach 194]

You are correct; Multicast is more efficient for Listen-Only Inputs and for Produced/Consumed Messages with multiple Consumers. Unicast connections were introduced for the sake of simplicity, because they do not require a correctly configured managed IP switching environment. If your application requires the efficiency that Multicast gives you, install managed Ethernet switches with IGMP Snooping and Querying correctly enabled and configured.