Edge-Core ECS4810-12M Layer 2 Management Manual page 499

(NR, RB) message without a DNF indication, all ring nodes
flush the FDB.
Recovery for Forced Switching – A Forced Switch command is
■
removed by issuing the Clear command (Configure Operation
page) to the same ring node where Forced Switch mode 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 Forced Switch was cleared continuously
transmits the R-APS (NR) message on both ring ports, informing
other nodes that no request is present at this ring node. The
ring nodes stop transmitting R-APS (NR) messages when they
accept an RAPS (NR, RB) message, or when another higher
priority request is received.
If the ring node where the Forced Switch was cleared receives
an R-APS (NR) message with a Node ID higher than its own
Node ID, it unblocks any ring port which does not have an SF
condition and stops transmitting R-APS (NR) message over both
ring ports.
Recovery with revertive mode is handled as follows:
■
The reception of an R-APS (NR) message causes the RPL
a.
Owner Node to start the WTB timer.
The WTB timer is cancelled if during the WTB period a
b.
higher priority request than NR is accepted by the RPL
Owner Node or is declared locally at the RPL Owner
Node.
When the WTB timer expires, in the absence of any other
c.
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.
The acceptance of the R-APS (NR, RB) message causes
d.
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:
■
The RPL Owner Node, upon reception of an R-APS(NR)
a.
message and in the absence of any other higher priority
request does not perform any action.
Then, after the operator issues the Clear command
b.
(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,
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C 14
HAPTER
Ethernet Ring Protection Switching