Cisco ONS 15454 DWDM Reference Manual page 485

Chapter 10 Network Reference
In CTC, domains are shown in the network view and reported as a list of spans. Each span is
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identified by a node/side pair, for example:
APC Domain Node_1 Side A, Node_4 Side B
+ Span 1: Node_1 Side A, Node_2 Side B
+ Span 2: Node_2 Side A, Node_3 Side B
+ Span 3: Node_3 Side A, Node_4 Side B
APC domains are not refreshed automatically; instead, they are refreshed using a Refresh button.
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Inside a domain, the APC algorithm designates a master node that is responsible for starting APC hourly
or every time a new circuit is provisioned or removed. Every time the master node signals APC to start,
gain and VOA setpoints are evaluated on all nodes in the network. If corrections are needed in different
nodes, they are always performed sequentially following the optical paths starting from the master node.
APC corrects the power level only if the variation exceeds the hysteresis thresholds of +/– 0.5 dB. Any
power level fluctuation within the threshold range is skipped since it is considered negligible. Because
APC is designed to follow slow time events, it skips corrections greater than 3 dB. This is the typical
total aging margin that is provisioned during the network design phase. After you provision the first
channel or the amplifiers are turned up for the first time, APC does not apply the 3 dB rule. In this case,
APC corrects all the power differences to turn up the node.
To avoid large power fluctuations, APC adjusts power levels incrementally. The maximum power
correction is +/– 0.5 dB. This is applied to each iteration until the optimal power level is reached. For
example, a gain deviation of 2 dB is corrected in four steps. Each of the four steps requires a complete
APC check on every node in the network. APC can correct up to a maximum of 3 dB on an hourly basis.
If degradation occurs over a longer time period, APC compensates for it by using all margins that you
provision during installation.
If no margin is available, adjustments cannot be made because setpoints exceed the ranges. APC
communicates the event to CTC, Cisco Transport Manager (CTM), and TL1 through an APC Fail
condition. APC clears the APC fail condition when the setpoints return to the allowed ranges.
APC can be manually disabled. In addition, APC automatically disables itself when:
An Hardware Fail (HF) alarm is raised by any card in any of the domain nodes.
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A Mismatch Equipment Alarm (MEA) is raised by any card in any of the domain nodes.
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An Improper Removal (IMPROPRMVL) alarm is raised by any card in any of the domain nodes.
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Gain Degrade (GAIN-HDEG), Power Degrade (OPWR-HDEG), and Power Fail (PWR-FAIL)
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alarms are raised by the output port of any amplifier card in any of the domain nodes.
A VOA degrade or fail alarm is raised by any of the cards in any of the domain nodes.
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The signaling protocol detects that one of the APC instances in any of the domain nodes is no longer
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reachable.
The APC state (Enable/Disable) is located on every node and can be retrieved by the CTC or TL1
interface. If an event that disables APC occurs in one of the network nodes, APC is disabled on all the
other nodes and the APC state changes to DISABLE - INTERNAL. The disabled state is raised only by
the node where the problem occurred to simplify troubleshooting.
APC raises the following minor, non-service-affecting alarms at the port level in CTC, TL1, and Simple
Network Management Protocol (SNMP):
APC Out of Range—APC cannot assign a new setpoint for a parameter that is allocated to a port
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because the new setpoint exceeds the parameter range.
APC Correction Skipped—APC skipped a correction to one parameter allocated to a port because
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the difference between the expected and current values exceeds the +/– 3 dB security range.
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10.4.2 APC at the Shelf Controller Layer
Cisco ONS 15454 DWDM Reference Manual, R8.5
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