Configuring Hardware and Communication Connections STEP 7.pdf

Configuring IRT Communication
Default Setting
When the communication relationship is created, media-redundant transmission is
disabled. This means that the data in an IRT communication relationship are
transmitted over precisely one path of the IRT network. If media redundancy is not
enabled, this means that the data are transmitted over exactly one path between
the IO controller and the IO device of the IRT network. If this path is interrupted,
then the data transfer will come to a halt.
Topology for Media-Redundant Transmission
To increase the reliability of data transmission, media-redundant transmission may
be used. When doing so, the topology must be configured so that there are at least
two different paths available between the sender switch and the receiver switch.
These paths are different when the switches for one path are not used by the other
one.
A ring topology would fulfill this need 100%. The device to be used as a switch
should be one that supports the planned IRT communication.
In addition, several rings can be combined with each other as long as the condition
is met that a switch is used in only precisely one path. If the topology of the
network will not allow this, then the paths must be as "resource-independent" as
possible. In case, however, media redundancy is not fully ensured.
The consistency check in HW Config will indicate whether switches between the
sender and the receiver are being used by more than one path.
In addition to being configured for media redundant transmission, the network also
requires a redundancy manager.
Function of the Redundancy Manager
The redundancy manager is an IO device that supports the planned IRT
communication and for which IRT topology must also be configured. This manager
is necessary in order to open the ring structures, which are necessary for mediaredundant
transmission, for TCP/IP frames. Otherwise, the TCP/IP frames would
continually circulate in the network. As far as IRT is concerned, the redundancy
manager is "porous" since IRT communication is running as planned and there are
thus no frames circulating in the network.
Configuring Hardware and Communication Connections with STEP 7
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