GE F650 User Manual page 238

B.1 PRP AND HSR ETHERNET PROTOCOLS
The two LANs, named LAN_A and LAN_B, are identical in protocol at the MAC level, but they can differ in performance and
topology. Transmission delays can also be different. The LANs have no direct connection among them and they are
assumed to be fail independent.
In some applications, only availability-critical nodes need a double attachment, while others do not. In order to meet the
specific requirements, PRP defines different kinds of end nodes.
• The Dual Attached Node (DAN) is connected to both LANs.
• Uncritical nodes can be attached to only one LAN and are therefore called Single Attached Nodes (SAN). SANs that
need to communicate with each other are on the same LAN.
• The Redundancy Box (RedBox) is used when a single interface node has to be attached to both networks. Such a node
can communicate with all other nodes. Since a node behind a RedBox appears for other nodes like a DAN, it is called
Virtual DANs (VDAN). The RedBox itself is a DAN and acts as a proxy on behalf of its VDANs. The RedBox has its own IP
address for management purposes
Similarly to PRP, HSR is based in the duplication of every frame sent, but in a ring topology. Each copy of the frame is
injected in a different direction of the ring. If any of the links between nodes is down, all nodes are still reachable. This
topology forces every node in the net to be HSR aware because they have to forward every message until it reaches its
destination. With that purpose, the redundancy information is located at the beginning of the frame allowing a faster
forwarding, see next figure.
B-2
Figure B-1: Example of PRP with two LANs (LAN A and LAN B)
F650 DIGITAL BAY CONTROLLER
APPENDIX B:
GEK-113000-AF