Unicast Connection over Ethernet/IP

[prakasha]

Hi everyone,

This has been 2nd time I am getting into the same question that in which circumstances we check the Unicast connection over ethernet/ip box while adding any ethernet/IP devices under EN2TR and When do We uncheck the Box. i went through so many documents still I am unable to understand it clearly. Please clarify in a simple way..

Thanks in advance..

 

[Contr_Conn]

Short answer: use Unicast if device supports it (most do) and this is not Redundancy System that does not support Unicast and only supports Multicast.
History behind it is that 20+ yeast ago EtherNet/IP IO was introduced as a multicast only. Multicast is efficient when sharing IO, but can flood networks if not managed, and can’t be routed.
IO Unicast was introduced later on.

 

[Tim Ganz]

Short answer: use Unicast if device supports it (most do) and this is not Redundancy System that does not support Unicast and only supports Multicast.
History behind it is that 20+ yeast ago EtherNet/IP IO was introduced as a multicast only. Multicast is efficient when sharing IO, but can flood networks if not managed, and can’t be routed.
IO Unicast was introduced later on.

What makes multicast good for sharing IO? and why did Rockwell start with it versus unicast?

Never heard of IO Unicast how is IO unicast and regular unicast different?

 

[Contr_Conn]

Multicast uses one packet on the wire to deliver data to multiple consumers. Example will be Input module is sending one data packet and multiple PLC are getting it. Or one Producer PLC sends data to multiple consumers using just one packet. In late 90s it was important for Ethernet modules with limited packet capacity and slow 10Mb networks, to reduce number of packets on the wire.
Modern networks and modules have much higher bandwidth and use of multiple packets is not an issue.
Unicast IO uses multiple packets for sharing data.