27.6.2 Using the Control VLAN's forwarding-delay-time

When the Ring Protocol runs from the initial status, such as for device startup and program restart (using the restart axrp operation command) for a transit node, data transfer VLANs are logically blocked. Transit nodes remove this logical block when they receive a flush control sent from the master node. However, when the program is restarted, if the failure monitoring time of the master node is long, the ring network status change may not be recognized. In this case, because the logical block is not released until the reception hold time for flush control frames (forwarding-shift-time) times out, the data VLAN for the transit node cannot communicate. Because operation is performed as follows when a forwarding transition time (forwarding-delay-time) is set for the control VLAN, this kind of case can be avoided.

1. The transit node performs an immediate logical block of the control VLAN during device startup or after program restart.

2. Because the control VLAN for the transit node has been logically blocked, a fault is detected on the master node (even though a fault was already detected previously upon device startup). Therefore, communication is switched to an alternate path.

3. The transit node removes Blocking for the control VLAN, due to a timeout of the forwarding transition time (forwarding-delay-time) for the control VLAN.

4. The master node receives a health check frame, detects recovery, and sends a flush control frame.

5. The transit node receives this flush control frame, and removes the logical block on the data transfer VLAN. With this, communication on the data transfer VLAN is restarted, and restoration of the normal communication path is performed on the entire ring network.

<Structure of this section>

• (1) Relation between control VLAN forwarding transition time (forwarding-delay-time) and flush control frame receive wait protection time (forwarding-shift-time)