Iprp - Siemens SIMATIC NET SCALANCE W780 Series Configuration Manual

4.9

iPRP

The "Parallel Redundancy Protocol" (PRP) is a redundancy protocol for cabled networks. It
is defined in Part 3 of the IEC 62439 standard.
With the "industrial Parallel Redundancy Protocol" (iPRP) the PRP technology can be used
in wireless networks. This improves the availability of wireless communication.
How it works
A PRP network consists of two completely independent networks. If one network is
disrupted, the frames are sent without interruption/reconfiguration via the parallel redundant
network. To achieve this the Ethernet frames are sent to the recipient in duplicate via both
networks. Devices capable of PRP have at least two separate Ethernet interfaces that are
connected to independent networks.
With devices not capable of PRP a redundancy box (RedBox) is connected upstream. This
allows access for so-called Single Attached Nodes (SAN) to PRP networks. The RedBox
duplicates every Ethernet frame to be sent and adds a PRP trailer to the frame that among
other things contains a sequence number. The RedBox simultaneously sends a copy of the
frame to the PRP A and PRP B network. At the receiving end the duplicate frame is
discarded by the RedBox. For this the RedBox requires certain transfer times designed for
Ethernet networks. For this reason using PRP in WLAN networks results in duplicate and
delayed frames.
With iPRP this problem is solved and the use of PRP in WLAN with SCALANCE W700
devices becomes possible
SCALANCE W780/W740 to IEEE 802.11n Web Based Management
Configuration Manual, 08/2018, C79000-G8976-C267-13
Technical basics
4.9 iPRP
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