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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