GE Reason H49 Technical Manual page 23

GE Reason H49
H49/EN M/C22
HSR is based on a ring-type architecture to achieve its network path redundancy.
Duplicate packets, identified as "A" and "B", are sent in opposite directions of the ring
to achieve redundancy down to the packet level. When a packet arrives at a DANH
node, the node will determine if the packet is addressed to it or to another
destination.
•
If the packet is addressed to the node, then
It will process it or

It will discard it if it is a duplicate packet

•
If the packet is for another destination, then
If the DANH device receives a frame that it originally sent, it does not

forward it
Otherwise, it will simply forward the packet on to the next node in the

network.
Frames sent by a SAN device (see "C" frames in the following figure) are converted
into two "A" and "B" frames and sent over the HSR network.
Received frames that are addressed to a SAN managed by a Redbox (such as MMS
messages) are not forwarded on to the HSR network.
There are two basic operation principles, depending on whether the broadcasted
frames are multicast (e.g. GOOSE) or unicast (e.g. MMS reports).
•
Multicast (e.g. GOOSE): A source DANH sends a frame over both ports ("A"-
frame and "B"-frame). The destination DANH receives, in a fault-free state, two
identical frames from each port within a certain interval, passes the first frame on
to its higher layers. A source DANH discards any duplicate multicast frame from
the ring.
•
Unicast (e.g. REPORT): A destination node of a unicast frame does not forward a
frame for which it is the only destination. It removes the unicast frame from the
ring.
Technical Manual
23