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Supplementary information
16.7 Basics and terminology of fault-tolerant communication
Redundancy nodes
Redundancy nodes represent extreme reliability of communication between two fault-tolerant
systems. A system with multi-channel components is represented by redundancy nodes.
Redundancy nodes are independent when the failure of a component within the node does
not result in any reliability impairment in other nodes.
Even with fault-tolerant communication, only single errors/faults can be tolerated. If more
than one error occurs between two communication end points, communication can no longer
be guaranteed.
Connection (S7 connection)
A connection represents the logical assignment of two communication peers for executing a
communication service. Every connection has two end points containing the information
required for addressing the communication peer as well as other attributes for establishing
the connection.
An S7 connection is the communication link between two standard CPUs or from a standard
CPU to a CPU in a fault-tolerant system.
In contrast to a fault-tolerant S7 connection, which contains at least two partial connections,
an S7 connection actually consists of just one connection. If that connection fails,
communication is terminated.
Figure 16-6
Note
Generally speaking, "connection" in this manual means a "configured S7 connection". For
other types of connection, refer to Manuals
SIMATIC NET NCM S7 for Industrial Ethernet
Fault-tolerant S7 connections
The requirement for higher availability with communication components (for example CPs
and buses) means that redundant communication connections are necessary between the
systems involved.
236
Example of an S7 connection
SIMATIC NET NCM S7 for PROFIBUS
.
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 10/2013, A5E32631667-AA
and
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