GE Reason H49, Техническое руководство

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Technical Manual GE Reason H49
24 H49/EN M/C22
4.4 HSR Quadbox
It is possible to connect two HSR rings when the traffic flow exceeds the capabilities
of a single ring. However, transmission delays from end to end are not improved. This
connection is possible thanks to quadruple port devices with forwarding capabilities
called QuadBoxes as shown in the following figure.
Although one QuadBox is sufficient to forward traffic, two QuadBoxes are used to
prevent a single point of failure. A QuadBox forwards frames over each ring as any
HSR node, and passes the frames unchanged to the other ring, except if the frame can
be identified as a frame not to be forwarded to the other ring. To this effect, a
QuadBox is expected to filter traffic based for instance on multicast filtering or on
VLAN filtering. There is no learning of MAC addresses in a QuadBox, though, since the
learning of MAC addresses on specific ports of a QuadBox device could lead to a short
break in communication if the QuadBox that has learned an address and is
forwarding network traffic fails.
With QuadBoxes realized as single physical entities, the two interconnected rings
share the same redundancy domain concerning fault tolerance. If one QuadBox
breaks down, both interconnected rings are in a degraded state and cannot tolerate a
further fault.
DANH
S1606ENa
DANH
DANH DANH
H49
QuadBox
H49
QuadBox
DANH DANH
DANH DANH
DANH
"A"
"B"
Source
Destination
“A” frames
“B” frames
frame is removed from the ring by the node
Figure 6: Two QuadBoxes linking two HSR Rings
The presence of two QuadBoxes on the same ring causes that two copies of the same
frame are transferred from the first ring to the second, each generating other two
copies.
This does not cause four frames to circulate on the second ring, since, when a copy
from a first QuadBox reaches the second QuadBox on the same second ring, the
second QuadBox will not forward it if it already sent a copy that came from its
interlink.