What are the modes of the HSR RedBox?

An industrial RedBox can provide all four listed interconnection modes. In HSR-SAN mode, it connects a singly attached node that does not natively support High-availability Seamless Redundancy to an HSR network. The RedBox duplicates frames entering the HSR domain and removes duplicate frames before delivering traffic to the SAN.

HSR-PRP mode interconnects an HSR ring with a Parallel Redundancy Protocol network while preserving seamless redundancy. PRP-PRP mode couples two PRP network domains, while HSR-HSR mode connects separate HSR rings. Depending on the implementation, the HSR-HSR interconnection function may also be described as a QuadBox function because four HSR-facing ports can be involved.

The essential RedBox responsibilities are frame conversion, duplication, duplicate elimination, sequence-number handling, and prevention of unintended forwarding loops between redundancy domains. HSR and PRP use compatible duplicate-identification principles, enabling controlled interconnection between these network types without introducing a single point of failure. RedBoxes also provide redundant connectivity for devices that have only one ordinary Ethernet interface.

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