VLANS, HMI vs I/O traffic..

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  • #2816
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      Hello everyone,

      I have a question regarding the importance of VLAN’s when it comes to segmenting the different types of traffic on your plant floor. I was talking to a controls engineer and I noticed that he mentioned that he Segments his Traffic to give priority to his I/O traffic…
      I thought that QoS was used for that purpose, VLAN’s were used to segment traffic on your network so that you don’t have to have physical segmentation. It would all be done Virtually so it was a more cost-effective¬†way to use your network resources?

      Your thoughts, thanks!


        Hi David,

        Physical segmentation was a method commonly used 5-10 years ago when Ethernet/IP IO devices started hitting the factory floors. It was common to house two Ethernet Bridge modules in your chassis to physically segment the IO traffic from the plant traffic.

        You’re right, through the use of managed network switches, IGMP Snooping features, and VLANs this practice is no longer needed or common place. Having two physically disjointed networks in your cell is probably easier to implement (knowledge of networking not really needed), however, more expensive to do so. Now you will need two of everything for each network. Also, it becomes cumbersome to diagnose and manage IO traffic when it is physically segmented like this.

        I would say physically segmenting your network like this is dated, and the “not so cheap” and dirty way to do it. A well planned network design is the only way to go!


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