Web Management Guide-R05

Chapter 13 | Basic Administration Protocols
Ethernet Ring Protection Switching
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not have an SF condition. This action subsequently unblocks the
traffic channel over the RPL.
e. A ring node accepting an R-APS (MS) message, without any local
higher priority requests stops transmitting R-APS messages.
f. A ring node receiving an R-APS (MS) message flushes its FDB.
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Protection switching on a manual switch request is completed
when the above actions are performed by each ring node. At
this point, traffic flows around the ring are resumed. From this
point on, the following rules apply regarding processing of
further manual switch commands:
a. While an existing manual switch request is present in the ring, any
new manual switch request is rejected. The request is rejected at
the ring node where the new request is issued and a notification is
generated to inform the operator that the new MS request was not
accepted.
b. A ring node with a local manual switch command which receives
an R-APS (MS) message with a different Node ID clears its manual
switch request and starts transmitting R-APS (NR) messages. The
ring node keeps the ring port blocked due to the previous manual
switch command.
c. An ring node with a local manual switch command that receives an
R-APS message or a local request of higher priority than R-APS (MS)
clear its manual switch request. The ring node then processes the
new higher priority request.
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Recovery for manual switching under revertive and non-
revertive mode is described under the Revertive parameter.
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Clear – Manually clears the protection state which has been invoked by a
forced switch or manual switch command, and the node is operating under
non-revertive mode; or before the WTR or WTB timer expires when the
node is operating in revertive mode.
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Two steps are required to make a ring operating in non-revertive
mode return to Idle state from forced switch or manual switch
state:
1. Issue a Clear command to remove the forced switch command on
the node where a local forced switch command is active.
2. Issue a Clear command on the RPL owner node to trigger the
reversion.
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The Clear command will also stop the WTR and WTB delay
timers and reset their values.