Testing vs Testing - the LAN

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As always - there is testing and there is testing ....

it depends on what is important to test.

The following are some of the aspects to be tested relative t the LAN itself

  • Message latency etc as performance of the network
  • LAN configuration - noting in particular that in 'conventional industrial ethernet', the switches would add/remove both priority and vlan tags from the messages as they so needed with the IEDs not really caring about these tags, whereas Substation LANs tend to need these tags set by the source, retained in transit and received by the destination without change.
  • It is VERY easy to mis-configure switches so that messages don't get to where they are supposed to - or get to where they are not supposed to - that involves your VLAN and/or multicast filtering
  • Trunk vs Edge configuration and what Ingress/Egress rules have been set
  • Correct Priority tag handling (and the type of handling of the priority level)
  • Port based security to make sure the right and only the right devices are connected to the right ports and locking down spare ports so nothing can be connected
  • Correctly set up any Port Mirroring to facilitate testing later
  • TX and Rx optical power levels
  • Redundancy and recovery times vs bumpless performance actually working
  • Functional configuration of the devices to publish and subscribe to all necessary messages, send/receive necessary MMS/Reports
  • Testing the facilities to be able to put things into test modes whilst the rest of the system is still in service


..... so it is important to test what is important - that needs thinking through for both the positive tests (it does what it is supposed to ) and the negative test (it does not do what it is not supposed to) and not just a collection of tests hoping things will be fine


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