SCADA Network Question

[seth350]

Hello everyone,
First I would like to say thank you Archie for a wonderful HMI!

I am going to be using AdvHMI for our new and first SCADA system.
I myself have never done one but from what I have seen, it is a plant HMI. All plant information in one place so to speak.
My question is how do other people typically setup their plant network? For example, we have a mixed network of two subnets. One is corporate controlled and is the DHCP server for all associate computers. The corporate range is 10.40.X.X. The other is a local network of which all the machines are connected. It's range is 192.168.16.X. There are around 30 machines, each with multiple Ethernet/ip devices. These two networks are connected somewhere that allows traffic to/from either network. Would it be wise to setup another subnet for communication to the SCADA PC? My worry is data collisions using the machine network. How have you guys done it?

[Archie]

I would guess that if you have 30 machines with Ethernet/IP devices all on the same network, it has quite a heavy load of network traffic. Ethernet/IP is not the most efficient protocol and takes a bit of planning and specific hardware to tame its extreme bandwidth usage.

When I deploy an HMI on a machine with Ethernet/IP devices, I use a second network card in the PLC for the HMI and if used, connection the plant network. This leaves all the heavy traffic on its own network and the lighter more tolerable traffic on its own network.

From your description it sounds like there is a router in your system that routes traffic between the plant network and PLC network. If you put the HMI PC on the PLC network, it will receive any multi-cast traffic that comes from the Ethernet/IP devices. Putting it on the plant network side will shield it from that traffic, but the requests and response still ultimately have to bridge to that network.

[seth350]

That is what I suspected Archie. The plc network was setup years ago and kind of haphazardly in my opinion.
I will plan on installing our own separate SCADA network and also see what I can do to tame the Ethernet/ip.
I suppose installing a gateway at each machine that filters multicast traffic would help?

[Archie]

It really depends on your PLC setup. On a PLC network with a lot of traffic the first thing I look for are things running as multicast that can be changed to unicast. I then check the RPIs to see if they can be set to a larger value. For example, if there is a scale in the system and the RPI is set to 10ms, that scale will be creating excess network traffic. Most scales only update 5-10 times per second, so an RPI has no reason to be faster than 50ms.

If the firmware of the PLC is older and doesn't allow unicast, then look at a possible update. If not, the only option may be a managed switch to route the packets. You could also use a managed switch at each machine to maintain the traffic to the IO local to the machine.