Siemens SCALANCE X-400 Operating Instructions Manual page 24

Description
3.2 Network topologies
An interruption of the ring can be caused by loss of the connection between two devices or
by failure of a device in the ring.
If the test frames of the redundancy manager no longer arrive at the other ring port because
of an interruption in the ring, the redundancy manager connects its two ring ports. This
substitute path once again restores a functioning connection between all remaining devices
in the form of a linear bus topology.
As soon as the interruption is eliminated, the original transmission paths are established
again, the two ring ports of the redundancy manager are disconnected and the redundancy
clients informed of the change. The redundancy clients then use the new paths to the other
devices.
The time between the ring interruption and restoration of a functional linear topology is
known as the reconfiguration time.
If the redundancy manager fails, the ring becomes a functional linear bus.
Media redundancy methods
The following media redundancy methods are supported by SIMATIC NET products:
● HRP (High Speed Redundancy Protocol)
Reconfiguration time: 0.3 seconds
● MRP (Media Redundancy Protocol)
Reconfiguration time: 0.2 seconds
The mechanisms of these methods are similar. HRP and MRP cannot be used in the ring at
the same time.
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Operating Instructions, 06/2015, C79000-G8976-C186-12
SCALANCE X-400