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Figure 20-22 Operation during shared link faults
(a) Operation for each node in a shared link monitoring ring
1. A ring fault is detected because HC(M)s are not received.
The master node can no longer receive HC(M)s from both directions, and detects a
ring fault. For details about master node and transit node operation during ring fault
detection, because operation is the same as multi-ring operation, see (1) Operation
when a fault is detected in 20.4.2 Operation for shared link faults and restoration.
2. Multi-fault monitoring frames cannot be received between shared links.
Shared nodes can no longer receive multi-fault monitoring frames between shared
links, but because reception is still possible on the other ring port, multi-fault
monitoring continues.
(b) Operation for each node in a backup ring
HC(M)s sent by the master node can no longer be received on a backup ring, but because
HC(S)s sent by shared nodes can be received, no fault operation is performed.
(2) Operation when multi-faults occur
The following figure shows operation when multi-faults occur due to shared link faults or
other link faults within a shared link monitoring ring.
20 Description of the Ring Protocol
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