Руководство Пользователя для Cisco Headend System Release 2.5
78-738186-01 Rev B
DHCT Status Reporting Utility
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What Causes DHCTs to Become Non-Responders?,
Continued
Hardware Failures on the DBDS Network
The following list contains some DBDS network components that could cause
DHCTs to become non-responders should the network components fail:
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QPSK Modulator/Demodulator
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Buffers full—Available memory for the standard operation of a modulator is
limited. Abnormal activity through the modulator may exhaust the available
memory and cause the modulator to reboot.
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DHCT chattering—Numerous DHCTs trying to simultaneously sign on to the
network may interfere with return path transmissions and cause modulators to
reboot.
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Excessive numbers of DHCTs assigned to modulator—Too many DHCTs
assigned to a single modulator may overwhelm the modulator.
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Router/switch
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The router or switch is improperly configured.
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The router or switch lacks sufficient processing capability. The router or switch
can act as a choke-point in the communication path. In extreme cases, the QPSK
modulator may reboot.
DBDS Configuration and Management Issues
The following list contains some conditions that might exist in the configuration of
the DNCS that may cause a DHCT to become a non-responder:
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Improper demodulator attenuation management—To maintain a communication
link with the QPSK demodulator, DHCTs should transmit at a level between (and
including) 25 to 55 dBmV (decibels with respect to 1 millivolt). Over time, DHCT
transmission levels may shift too high or too low. The shifting levels may cause
significant numbers of DHCTs assigned to a demodulator to become non-
responders.
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Improper DHCT inventory management—The DNCS database may fall out of
synchronization with the database of the billing vendor. This loss of
synchronization may cause the DNCS to try to poll DHCTs that are not actually in
subscribers’ homes.
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Failure to run the updateOUI utility—DHCTs that attempt to sign on to the
network using an incorrect organizationally unique identifier (OUI) are
unsuccessful.
Note: Chapter 11, Update the DHCT OUI With the updateOUI Utility, of the
Note: Chapter 11, Update the DHCT OUI With the updateOUI Utility, of the
DNCS Utilities Installation and Operation Guide, part number 740020, provides
instructions to ensure that DHCTs have the correct OUI before they try to sign on
to the network.