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
- 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,
message over both ring ports, informing the Ethernet ring that the RPL is blocked, and
performing a flush FDB action. The ERPS 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
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.