Specifications

ALAXALA Ring Configuration Guide (Edition 1)

2.2.2 Operation during a failure

When a failure occurs in a single ring, the Ring Protocol works as follows:

Figure 2.2-2 Single ring operation during a failure

(1) Master node operation

If the master node detects a failure in the ring, the node takes actions as follows:

[1] Changing the data transfer VLAN status

The master node changes the status of the secondary port used for the ring VLAN group for data

transfer to the Forwarding status. After the ring failure is detected, the ring VLAN statuses of the master

node are as follows:

Ring port (primary): Forwarding (not changed)

Ring port (secondary): Blocking -> Forwarding

[2] Sending flush control frames

When the master node detects the failure, the node sends flush control frames from its two ring ports.

The master node sends the flush control frames several times from each ring port to ensure that the

frames are actually sent out.

[3] Clearing the MAC address table

To minimize the impact of flooding caused by a ring topology change, MAC address table entries are

not cleared if their output destinations are assigned to ports other than ring ports. MAC address table

entries are cleared only if an entry has an output VLAN that belongs to the ring VLAN group for data

transfer and its output destination is a ring port.

[4] If flush control frames are received

Flush control frames are forwarded from one transit node to another and usually discarded at the

failure point. Therefore, in general, flush control frames do not come back to the master node. If the

master node receives flush control frames, the node discards them.

[5] Transition of the ring status to the recovery monitoring status

After the master node detects the ring failure, the master node status changes from the failure

monitoring status to the recovery monitoring status.

(2) Transit node operation

During a ring failure, a transit node receives several flush control frames on the ring port. A transit node

performs steps [1] and [2] below when the first flush control frame arrives. Then, when the transit node receives

the subsequent flush control frames during step [2], the node performs step [3]. If the node receives the

subsequent frames after step [2] is completed, the node clears the table again.

[1] Forwarding of flush control frames to the next destination

[2] Clearing the MAC address table

The MAC address table entries whose output destination is one of the ring ports are cleared.

[3] Forwarding of flush control frames to the next destination

failure occurs.

Ring VLAN: BLK -> FWD

T1 M T5

T2 T3 T4

Flush control

frames