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Figure 20-12 Normal operation for shared link monitoring rings
(a) Master node operation
To prevent fault misdetection due to one-way link faults, health check frames (HC(M)s) are
sent from two ring ports. Monitoring is performed to check that HC(M)s in both directions
are received within the pre-determined time. Data frame transfer is performed on the
primary port. Because the secondary port is logically blocked, data frame transfer and MAC
address learning are not performed.
(b) Transit node operation
Transit node operation is the same as for single rings. Transit nodes do not monitor the
HC(M)s sent by the master node. When an HC(M) is received, it is transferred to the next
node in the ring. Data frame transfer is performed on both ring ports.
20.4.2 Operation for shared link faults and restoration
The following explains faults and restoration operations when a fault occurs between
shared links for a multi-ring configuration with shared links.
(1) Operation when a fault is detected
The following figure shows operation for when a shared link fault is detected.
20 Description of the Ring Protocol
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