Revertive and Non-revertive Mode

In the revertive mode, you can revert back to the RPL being blocked once the Signal Fault has cleared. In non-revertive mode, the SF remains blocked even after the fault clears. Reversion is handled in the following way:

The reception of an R-APS No Request (NR) message causes the RPL owner node to start the wait-to-restore (WTR) timer.
The WTR timer is cancelled if, during the WTR period, a request with a higher priority than NR is accepted by the RPL owner node, or is declared locally at the RPL owner node.
When the WTR timer expires, without the presence of any other higher priority request, the RPL owner node initiates reversion by blocking its traffic channel over the RPL, transmitting an R-APS (NR, RB) message over both ring ports, informing the Ethernet ring that the RPL is blocked, and performing a flush FDB (forwarding database) action. The ERPS (Ethernet Ring Protection Switching) Ring will be in the idle state.
The acceptance of the R-APS (NR, RB) message causes all Ethernet ring nodes to unblock any blocked non-RPL link that does not have an SF condition. If it is an R-APS (NR, RB) message without a DNF indication, all Ethernet ring nodes perform a necessary flush FDB action.

In non-revertive operation, the Ethernet ring does not automatically revert when all ring links and Ethernet ring nodes have recovered and no external requests are active. Non-revertive operation is handled in the following way:

The RPL owner node does not generate a response on reception of an R-APS (NR) messages.
When other healthy Ethernet ring nodes receive the NR (node ID) message, no action is taken in response to the message.

Published March 2020prev | next

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