Edge-Core ECS4660-28F, Management Manual, Page: 535 / 2020

C
HAPTER
14
| Basic Administration Protocols
Ethernet Ring Protection Switching
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c.
The acceptance of the R-APS (NR, RB) message triggers
all ring nodes to unblock any blocked non-RPL which
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 result of an operator command.
■
Recovery for Manual Switching – A Manual Switch command is
removed by issuing the Clear command (Configure Operation
page) at the same ring node where the Manual Switch 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 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:
a.
The RPL Owner Node, upon reception of an R-APS (NR)
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.
b.
When the WTB timer expires, it generates the WTB
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.
c.
The acceptance of the R-APS (NR, RB) message causes
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.