The second frame received is recognized and discarded. This achieves N-1 redundancy
without reconfiguration (= bumpless switchover).
Note
Overlong frames
When a SCALANCE X204RNA IE switch feeds a frame with the maximum length into a PRP
network, the IE switch appends a PRP trailer to the frame. Appending the PRP trailer results
in an overlong frame that exceeds the maximum permitted frame length (according to the IEEE
802.3 standard).
To prevent data loss with overlong frames, all network components located in a PRP network
must support a frame length of at least 1528 bytes.
You will find a list of compatible devices that support processing of overlong frames in the
section "PRP-compatible devices (Page 149)".
There are already end devices equipped with two Ethernet interfaces that are capable of
handling the "Parallel Redundancy Protocol" (Double Attached Nodes PRP = DANP).
On the other hand, there are many end devices starting with S7 controllers right through to
control computers that communicate using TCP/IP but do not support PRP, and some even
have only one Ethernet Interface. With all these devices, a SCALANCE X-200RNA can be
connected upstream from them. This allows access for Single Attached Nodes (SAN) to PRP
networks.
Industrial Ethernet bus (linear), star or ring structures with switching functionality can be
implemented cost-effectively with devices of the SCALANCE X product line. You will find a list
of usable network components in "Accessories and compatible devices (Page 147)".
Network topologies and redundancy
3.1 PRP
SCALANCE X-200RNA
Operating Instructions, 10/2016, C79000-G8976-C342-04
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Summary of Contents for SCALANCE X-200RNA
Page 6: ...Table of contents SCALANCE X 200RNA 6 Operating Instructions 10 2016 C79000 G8976 C342 04 ...
Page 12: ...Introduction SCALANCE X 200RNA 12 Operating Instructions 10 2016 C79000 G8976 C342 04 ...
Page 16: ...Safety notices SCALANCE X 200RNA 16 Operating Instructions 10 2016 C79000 G8976 C342 04 ...
