29.4.2 Operation in case of shared link failure and recovery

The following explains faults and restoration operations when a fault occurs between shared links for a multi-ring configuration with shared links.

<Structure of this section>

(1) Actions when failures are detected

The following figure shows operation for when a shared link fault is detected.

Figure 29-16: Operation when a shared link fails

(a) Master node operation of shared link monitoring ring

When a fault occurs on a shared link, the master node can no longer receive HC(M)s from both directions, and a ring fault is detected. As with a single ring, the following fault operations are performed for the master node detecting the fault:

The VLAN status of the ring for data transfer is changed.

Flush control frames are sent.

The MAC address table is cleared.

The monitoring status is changed.

(b) Transit Node Operation for Shared Link Monitoring Ring

As with single rings, the following operations are performed when a flush control frame sent from the master node is received:

Flush control frames are transferred.

The MAC address table is cleared.

(c) Master and Transit Node Behavior for Shared Link Non-Monitoring Rings

Because the master node in a shared link non-monitoring ring does not detect ring faults for shared links, no fault operations are performed. Therefore, path switching does not occur for transit nodes.

(2) Operation when recovery is detected

The following figure shows operation when recovery from a fault is detected for a shared link.

Figure 29-17: Operation during shared link recovery

(a) Master node operation of shared link monitoring ring

When a ring fault has been detected, and the master node receives an HC(M) it sent itself, it determines that recovery from the ring fault has occurred. As with a single ring, the following restoration operations are performed:

The VLAN status of the ring for data transfer is changed.

Flush control frames are sent.

The MAC address table is cleared.

The monitoring status is changed.

(b) Transit Node Operation for Shared Link Monitoring Ring

As with single rings, the following operations are performed when a flush control frame sent from the master node is received:

Flush control frames are transferred.

The MAC address table is cleared.

(c) Master and Transit Node Behavior for Shared Link Non-Monitoring Rings

Because the master node in a shared link non-monitoring ring does not detect ring faults, no restoration is performed, including for transit nodes.