Handling Client And Server Certificates - Siemens SIMATIC ET 200AL System Manual

Minimum sampling interval
With "Minimum sampling interval", you set the time intervals at which the OPC UA server
records the value of a CPU tag and compares it with the previous value to detect any
changes.
If the sampling interval is selected smaller than the publishing interval, and an OPC UA client
requests such a high sampling rate for certain PLC tags, two or more values may be
measured during each publishing interval.
In this case, the OPC UA server writes the value changes into the queue and sends all value
changes to the client after the completion of the publishing interval. If more value changes
occur in the publishing interval than fit in the queue, the OPC UA server overwrites the oldest
values. (depending on the set "Discard Policy", the option "Discard Oldest" has to be
activated in this case). The most recent values are sent to the client.
Maximum number of monitored elements (monitored items)
In this field, you specify the maximum number of elements that the OPC UA server of the
CPU simultaneously monitors for a value change.
The monitoring ties up resources. The maximum number of monitored elements is
dependent on the utilized CPU.
9.3.2.5

Handling client and server certificates

A secure connection between the OPC UA server and an OPC UA client is only established
when the server can prove its identity to the client. This is done with the server certificate.
Certificate of the OPC UA server
When you have activated the OPC UA server and have confirmed the security prompts,
STEP 7 automatically generates the certificate for the server and saves it in the local
certificate directory of the CPU. You can view and manage this directory with the local
certificate manager of the CPU (exporting or deleting certificates).
The figure below shows the local certificate manager of the CPU with the automatically
generated certificate for the OPC UA server:
Figure 9-9
Communication
Function Manual, 12/2017, A5E03735815-AF
Local certificate manager of the CPU
OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
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