Edge-Core ECS4660-28F, Management Manual, Page: 1330 / 2020

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| ERPS Commands
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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 erps 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 155 on page 1328 ). 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.
◆ 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.