ECS4510 Series Web Management Guide-R03

Chapter 13 | Basic Administration Protocols
Ethernet Ring Protection Switching
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Manual Switch – Blocks specified ring port, in the absence of a failure or an
FS command. (Options: West or East)
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A ring with no request has a logical topology with the traffic channel
blocked at the RPL and unblocked on all other ring links. In this
situation, the Manual Switch command triggers protection switching as
follows:
a. If no other higher priority commands exist, the ring node, where a
manual switch command was issued, blocks the traffic channel and
R-APS channel on the ring port to which the command was issued,
and unblocks the other ring port.
b. If no other higher priority commands exist, the ring node where the
manual switch command was issued transmits R-APS messages
over both ring ports indicating MS. R-APS (MS) message are
continuously transmitted by this ring node while the local MS
command is the ring node’s highest priority command (see
Table 30 on page 475). The R-APS (MS) message informs other ring
nodes of the MS command and that the traffic channel is blocked
on one ring port.
c. If no other higher priority commands exist and assuming the ring
node was in Idle state before the manual switch command was
issued, the ring node flushes its local FDB.
d. A ring node accepting an R-APS (MS) message, without any local
higher priority requests unblocks any blocked ring port which does
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.