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.