GE P24DM - High-Availability Seamless Redundancy (HSR); HSR Multicast Topology; Figure 147: IED Attached to Separate Lans

Boxes (sometimes abbreviated to RedBox). Devices with a single Ethernet port that connect to both LANs by
means of a R
edBox are known as Virtual DAN (VDAN).
The figure below summarises DAN, SAN, VDAN, LAN, and RedBox connectivity.
VDAN
VDAN
VDAN
REDUNDANCY
BOX
SAN SAN
SAN
DAN
DAN
DAN
LAN A
LAN B
E01028
Figure 147: IED attached to separate LANs
In a D
AN, both ports share the same MAC address so it does not affect the way devices talk to each other in an
Ethernet network (Address Resolution Protocol at layer 2). Every data frame is seen by both ports.
When a DAN sends a frame of data, the frame is duplicated on both ports and therefore on both LAN segments.
This provides a redundant path for the data frame if one of the segments fails. Under normal conditions, both LAN
segments are working and each port receives identical frames.
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.
Chapter 16 - Communications P24xM
312 P24xM-TM-EN-2.1