Figure 87: Combined Prp And Hsr Networks - ABB UniGear Series Engineering Manual

Combined Parallel Redundancy Protocol (PRP) and High Availability Seamless Redundancy
(HSR) networks
Combining PRP and HSR networks can be overcome some drawback of pure PRP or HSR net-
work. PRP and HSR protocols have been developed to work interoperable, because HSR ring
applies the PRP principle of parallel operation to a single ring. PRP networks and HSR rings
are coupled through PRP / HSR redboxes. Two redboxes should be used per one ring to be
redundant and have access to both PRP networks. If one Redbox fails the seamless redun-
dancy is still available through the other. The redboxes divide HSR ring in two parts of equal
size minimizing the maximum number of hops.
Figure 87 : Combined PRP and HSR networks
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