Web Management Guide-R04

Table Of Contents
Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
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Recovery with revertive mode is handled as follows:
a. The reception of an R-APS (NR) message causes the RPL Owner
Node to start the WTB timer.
b. The WTB timer is cancelled if during the WTB period a higher
priority request than NR is accepted by the RPL Owner Node or
is declared locally at the RPL Owner Node.
c. When the WTB timer expires, in the absence of any other higher
priority request, the RPL Owner Node initiates reversion by
blocking the traffic channel over the RPL, transmitting an R-APS
(NR, RB) message over both ring ports, informing the ring that
the RPL is blocked, and flushes the FDB.
d. The acceptance of the R-APS (NR, RB) message causes all ring
nodes to unblock any blocked non-RPL that does not have an
SF condition. If it is an R-APS (NR, RB) message without a DNF
indication, all ring nodes flush their FDB. This action unblocks
the ring port which was blocked as a result of an operator
command.
Recovery with non-revertive mode is handled as follows:
a. The RPL Owner Node, upon reception of an R-APS(NR) message
and in the absence of any other higher priority request does
not perform any action.
b. Then, after the operator issues the Clear command (Configure
Operation page) at the RPL Owner Node, this ring node blocks
the ring port attached to the RPL, transmits an R-APS (NR, RB)
message on both ring ports, informing the ring that the RPL is
blocked, and flushes its FDB.
c. The acceptance of the R-APS (NR, RB) message triggers all ring
nodes to unblock any blocked non-RPL which does not have an
SF condition. If it is an R-APS (NR, RB) message without a DNF
indication, all ring nodes flush their FDB. This action unblocks
the ring port which was blocked as result of an operator
command.
Recovery for Manual Switching – A Manual Switch command is
removed by issuing the Clear command (Configure Operation page) at
the same ring node where the Manual Switch is in effect. The clear
command removes any existing local operator commands, and triggers
reversion if the ring is in revertive behavior mode.
The ring node where the Manual Switch was cleared keeps the ring
port blocked for the traffic channel and for the R-APS channel, due to
the previous Manual Switch command. This ring port is kept blocked
until the RPL is blocked as a result of ring protection reversion, or until
there is another higher priority request (e.g., an SF condition) in the
ring.