5.3 HIGH-AVAILABILITY SEAMLESS REDUNDANCY (HSR)
HSR is standardized in IEC 62439-3 (clause 5) for use in ring topology networks. Similar to PRP, HSR provides
bumpless r
edundancy and meets the most demanding needs of substation automation. HSR has become the
reference standard for ring-topology networks in the substation environment. The HSR implementation of the
redundancy Ethernet board (REB) is compatible with any standard HSR device.
HSR works on the premise that each device connected in the ring is a doubly attached node running HSR (referred
to as DANH). Similar to PRP, singly attached nodes such as printers are connected via Ethernet Redundancy Boxes
(RedBox).
5.3.1 HSR MULTICAST TOPOLOGY
When a DANH is sending a multicast frame, the frame (C frame) is duplicated (A frame and B frame), and each
duplicate frame A/B is tagged with the destination MA
C address and the sequence number. The frames A and B
differ only in their sequence number, which is used to identify one frame from the other. Each frame is sent to the
network via a separate port. The destination DANH receives two identical frames, removes the HSR tag of the first
frame received and passes this (frame D) on for processing. The other duplicate frame is discarded. The nodes
forward frames from one port to the other unless it was the node that injected it into the ring.
DANH
Source
DANH Redbox
DANH DANH DANH
A frame B frame
C frame
Switch
Singly Attached
Nodes
D frameD frame
D frameD frameD frame
V01030
Figure 172: HSR multicast topology
Only about half of the netw
ork bandwidth is available in HSR for multicast or broadcast frames because both
duplicate frames A & B circulate the full ring.
P54A/B/C/E Chapter 17 - Communications
P54xMED-TM-EN-1 351
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