Manual Switch
Manual Switch is similar to the Force Switch except that only one Manual
Switch is allowed for an Ethernet ring. The processing of which node retains the Manual Switch
is based on the priority table and the node state. However only one Manual Switch is retained
at the end for the ring.
Clearing the Manual Switch is done similar to the Force Switch.
Virtual Channel for Sub-rings
While the standard describes how the sub-rings can function with a virtual channel, in this
implementation sub-rings will function only with the presence of virtual channels.
Channel Blocking
The R-APS control channel is blocked, as is traffic on the blocked ports for the control
traffic entering on one ring port and getting forwarded to the other ring port. However, locally
generated or delivered control traffic on the blocked port is supported.
Traffic Blocking
Traffic is always blocked for the protected VLANs on the blocked ports of
the ring/sub-ring in a G.8032 network.
Signal Failure and Recovery
In the absence of a higher priority request in the node, the following
Signal Failure (SF) actions are taken.
- An Ethernet ring node detecting an SF condition on one of its ring
ports blocks the traffic channel and R-APS channel on the failed ring port.
- The Ethernet ring node detecting an SF condition transmits an R-APS
message indicating SF on both ring ports. The R-APS (SF) message informs other Ethernet
ring nodes of the SF condition. R-APS (SF) messages are continuously transmitted by the
Ethernet ring node detecting the SF condition while this condition persists. (The Periodic
timer determines the interval of sending the SF after the first three.) For sub-ring
interconnection nodes, the R-APS (SF) message is transmitted on the R-APS channel of the
Sub-Ring port.
- Assuming the Ethernet ring node was in an idle state before the SF
condition occurred, upon detection of this SF condition the Ethernet ring node triggers
a local FDB (forwarding database) flush.
- An Ethernet ring node accepting an R-APS (SF) message unblocks any
blocked ring port that does not have an SF condition. This action unblocks the traffic
channel on the RPL.
- An Ethernet ring node accepting an R-APS (SF) message stops
transmission of other R-APS messages.
- An Ethernet ring node accepting an R-APS (SF) message without a DNF
indication performs a flush FDB.
An Ethernet ring node that has one or more ring ports in an SF condition (upon
detection of clearance of the SF condition) keeps at least one of these ring ports blocked
for the traffic channel and for the R-APS channel, until the RPL is blocked as a result of
Ethernet ring protection reversion, or until there is another higher priority request (for
example, an SF condition) in the Ethernet ring. An Ethernet ring node that has one ring port
in an SF condition, and detects clearing of this SF condition, continuously transmits the
R-APS (NR) message with its own Node ID as the priority information over both ring ports,
informing that no request is present at the Ethernet ring node and initiates a guard timer
as described in sub-clause 10.1.5. Another recovered Ethernet ring node (or Nodes) holding
the link block receives the message and compares the Node ID information with its own Node
ID. If the received R-APS (NR) message has the higher priority, the Ethernet ring node
unblocks its ring ports. Otherwise, the block remains unchanged. There is only one link with
one-end block. The Ethernet ring nodes stop transmitting R-APS (NR) messages when they
accept an R-APS (NR, RB), or when another higher priority request is received
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