Motorola APEX1000 Installation And Operation Manual page 268

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The Low Bit Rate Alarm is set to Critical whenever any GigE input stream falls
below the specified input data rate. For MPTS Redundancy, this alarm's purpose is
to alert users that the Secondary stream is no longer available. However, this alarm
can also indicate a low Primary input rate, in the event that the data rate drops at the
same time for both the Primary and Secondary input streams. The alarm clears when
all input streams are above the specific low bit rate.
Low Bit Rate Alarm
You can configure any GigE input stream to have the input rate monitored for a low bit
rate by using the same window as redundancy is configured, but you only need to select
a low bit rate and a comparison type (data rate or stream rate). The APEX1000 will then
set an alarm and issue a trap whenever any GigE input stream falls below the specified
low bit rate.
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An overall alarm is maintained to indicate the status of all input streams being
monitored.
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Traps are issued for each input stream when the alarm condition for that input
stream changes.
Low Bit Rate Error Factor
The low bit rate checking uses a five percent error factor based on the input rate you
enter. In view of the fact that the input GigE packet counts are done prior to network de-
jittering (due to fluctuations in the network), the low bit rate needs to allow for variations
in the actual rate. The APEX1000 takes the rate you enter and multiplies this by 95% to
calculate the actual rate that will be used for comparison against the actual input rate.
This five percent error factor allows for enough deviation to prevent unwanted alarms,
while at the same time allowing for the alarming of real low bit rate streams.
The five percent error factoring is done internally by the APEX1000, rather than requiring
a user to know what a specific input rate should be. Typically, for an input stream rate of
38.81, various users would enter this low bit rate as 38.8, 38.8107, 38.0, etc. This error
factor also removes this issue from the user, thereby preventing unintentional alarms.
For example, factors for the rates listed above would yield the following low bit rate
alarm levels:
1. — 38.8 Mbps = 36.86 Mbps
2. — 38.81 Mbps = 36.8695 Mbps
3. — 38.0 Mbps = 36.1 Mbps
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APEX1000 All-Purpose Edge QAM Software Version 2.4.x • Installation and Operation Manual
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