Edge-Core ECS4110-28T Management Manual page 507

C
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.
The Ethernet Ring Node where the Manual Switch was cleared
continuously transmits the R-APS (NR) message on both ring
ports, informing 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 Manual 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 on both
ring ports.
Recovery with 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, starts the WTB timer and waits for it to expire.
While the WTB timer is running, any latent R-APS (MS)
message is ignored due to the higher priority of the WTB
running signal.
When the WTB timer expires, it generates the WTB
b.
expire signal. The RPL Owner Node, upon reception of
this signal, initiates reversion by blocking the traffic
channel on the RPL, transmitting an R-APS (NR, RB)
message over both ring ports, informing the ring that the
RPL is blocked, and flushes its FDB.
The acceptance of the R-APS (NR, RB) message causes
c.
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 Ethernet 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 over both ring
ports, informing the ring that the RPL is blocked, and
flushes its FDB.
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| Basic Administration Protocols
14
HAPTER
Ethernet Ring Protection Switching