Operating Mechanism
- Polling mechanism
The polling mechanism is a mechanism that the master node of the EIPS ring actively detects the integrity of the ring.
The master node sends the Hello packet from the primary port periodically and the packets are transmitted over all transmission nodes. If the ring is healthy, the secondary port on the master node will receive the Hello packet before timing out and the master node will keep the secondary port in the blocked state. If the ring is broken, the secondary port on the master node cannot receive the Hello packet before timing out and the master node will unblock the data VLANs at the secondary port and send the COMM-FLUSH-FDB packet to all transmission nodes to update their own forwarding table entries.
- Link-down alarm mechanism
When any port on the transmission node or the edge node is Down on the EIPS ring, it will send the Link-Down packet to the master node at once. When the master node receives the Link-Down packet, it unblocks the data VLANs at its secondary port and sends the COMM-FLUSH-FDB packet to all transmission nodes and edge nodes to update their own forwarding table entries. After the nodes update their forwarding table entries, the data flow is switched to a normal link.
- Ring recovery mechanism
When any port on the transmission node or the edge node is Up again on the EIPS ring, the master node may discover the ring recovery after a period of time. The network may form a temporary ring and generate broadcast storm for data VLANs.
To prevent generating temporary ring, when the standby node finds its port connecting to the ring is Up again, the standby node temporarily blocks the port (only the packets of control VLANs are permitted to pass). When it is sure that no loop will be caused, the port is unblocked.
- Load balancing mechanism
Multiple EIPS domains are configured on the same Ethernet ring and send the traffic of different data VLANs. That is, different VLAN traffics are forwarded along different paths, resulting in load balancing.
- Standby node mechanism
The transmission node directly connected to the secondary port on the master node is considered as a standby node. When the master node operates normally, the standby node works as a transmission node; when the master node breaks down, the standby node works as a master node.
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