Siemens SIMATIC ET 200AL, System Manual

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Glossary
Communication
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Function Manual, 05/2021, A5E03735815-AJ
SDA service
Send Data with Acknowledge. SDA is an elementary service with which an initiator (for
example DP master) can send a message to other devices and then receives acknowledgment
of receipt immediately afterwards.
SDN service
Send Data with No Acknowledge. This service is used primarily to send data to multiple
stations and the service therefore remains unacknowledged. Suitable for synchronization
tasks and status messages.
Security
Generic term for all the measures taken to protect against
•
Loss of confidentiality due to unauthorized access to data
• Loss of integrity due to manipulation of data
• Loss of availability due to the destruction of data
Self-signed certificates
These are certificates that you sign with your private key and use as end-entity certificates.
The signature of these end-entity certificates is verified with your public key.
The "Subject" and "Issuer" attributes of self-signed certificates must be identical: You have
signed your certificate yourself.
The "CA" field must be set to "False".
You can, for example, use self-signed certificates as application certificates for an OPC UA
client.
The procedure required to generate a self-signed certificate with the certificate generator of
the OPC Foundation is described here (Page ).
Server
A device or more generally an object that can provide certain services; the service is
performed at the request of a client.
Slave
Distributed device in a fieldbus system that can only exchange data with a master after the
master has requested this.
→ See also DP slave