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 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
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.
