Digisol DG-FS4526E, Management Manual

Page: 434 / 1162

C
HAPTER
15 | Basic Administration Protocols
Ethernet Ring Protection Switching
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west should be the next node in the ring in a counter-clockwise
direction.
Once configured, this field shows the ring port for this node, and the
interface state:
Blocking – The transmission and reception of traffic is blocked and
the forwarding of R-APS messages is blocked, but the transmission
of locally generated R-APS messages is allowed and the reception of
all R-APS messages is allowed.
Forwarding – The transmission and reception of traffic is allowed;
transmission, reception and forwarding of R-APS messages is
allowed.
Down – The interface is not linked up.
Unknown – The interface is not in a known state.
East Port – Connects to next ring node to the east.
RPL Port – If node is connected to the RPL, this shows by which
interface.
RPL Owner – Configures a ring node to be the Ring Protection Link
(RPL) owner.
Holdoff Timer – The hold-off timer is used to filter out intermittent
link faults. Faults will only be reported to the ring protection mechanism
if this timer expires. (Range: 0-10000 milliseconds, in steps of 100
milliseconds)
In order to coordinate timing of protection switches at multiple layers, a
hold-off timer may be required. Its purpose is to allow, for example, a
server layer protection switch to have a chance to fix the problem
before switching at a client layer.
When a new defect or more severe defect occurs (new Signal Failure),
this event will not be reported immediately to the protection switching
mechanism if the provisioned hold-off timer value is non-zero. Instead,
the hold-off timer will be started. When the timer expires, whether a
defect still exists or not, the timer will be checked. If one does exist,
that defect will be reported to the protection switching mechanism. The
reported defect need not be the same one that started the timer.
Guard Timer – The guard timer is used to prevent ring nodes from
receiving outdated R-APS messages. During the duration of the guard
timer, all received R-APS messages are ignored by the ring protection
control process, giving time for old messages still circulating on the ring
to expire. (Range: 10-2000 milliseconds, in steps of 10 milliseconds)
The guard timer duration should be greater than the maximum
expected forwarding delay for an R-APS message to pass around the
ring. A side-effect of the guard timer is that during its duration, a node
will be unaware of new or existing ring requests transmitted from other
nodes.