3-5RRPP TimersWhen RRPP checks the link state of an Ethernet ring, the master node sends Hello packets out theprimary port according to the Hello timer and determines whether its secondary port receives the Hellopackets based on the Fail timer.z The Hello timer specifies the interval at which the master node sends Hello packets out theprimary port.z The Fail timer specifies the maximum delay between the master node sending Hello packets outthe primary port and the secondary port receiving the Hello packets from the primary port. If thesecondary port receives the Hello packets sent by the local master node before the Fail timerexpires, the overall ring is in Health state. Otherwise, the ring transits into Disconnect state.In an RRPP domain, a transit node learns the Hello timer value and the Fail timer value on the masternode through the received Hello packets, ensuring that all nodes in the ring network are consistent inthe two timer settings.How RRPP WorksPolling mechanismThe polling mechanism is used by the master node of an RRPP ring to check the Health state of thering network.The master node sends Hello packets out its primary port periodically, and these Hello packets travelthrough each transit node on the ring in turn.z If the ring is complete, the secondary port of the master node will receive Hello packets before theFail timer expires and the master node will keep the secondary port blocked.z If the ring is torn down, the secondary port of the master node will fail to receive Hello packetsbefore the Fail timer expires. The master node will release the secondary port from blocking dataVLANs while sending Common-Flush-FDB packets to instruct all transit nodes to update their ownMAC entries and ARP/ND entries.Link down alarm mechanismThe transit node, the edge node or the assistant-edge node sends Link-Down packets to the masternode immediately when they find any of its own ports belonging to an RRPP domain is down. Upon thereceipt of a Link-Down packet, the master node releases the secondary port from blocking data VLANswhile sending Common-Flush-FDB packet to instruct all the transit nodes, the edge nodes and theassistant-edge nodes to update their own MAC entries and ARP/ND entries. After each node updatesits own entries, traffic is switched to the normal link.
