Руководство По Проектированию для Cisco DNCS System Release 2.7 3.7 4.2
4000358 Rev B
Introducing DOCSIS
1-25
DHCT Communication Modes
Introduction
This section describes the DHCT Communication Modes (DCMs) used by DOCSIS-
capable DHCTs within a DBDS environment.
The DOCSIS-capable DHCT is instructed to use a specific DHCT communication
The DOCSIS-capable DHCT is instructed to use a specific DHCT communication
mode through a DCM setting. The DNCS operator defines the communication mode
on the DNCS. The DNCS embeds the mode in the UNConfigIndication message.
This small message is periodically broadcasted on the downstream DAVIC out-of-
band QPSK signals and on the CMTS downstream channels through DSG
definitions.
The DCM indicates which DHCT Communication Mode is to be used:
•
The DCM indicates which DHCT Communication Mode is to be used:
•
DAVIC
•
Mixed DOCSIS/DAVIC
•
DOCSIS
The DCM is ignored by DHCTs that are not DOCSIS-capable.
The DCM is common to all DHCTs within the span of control of a single
The DCM is common to all DHCTs within the span of control of a single
downstream DAVIC out-of-band QPSK transmitter or a single DSG definition on a
CMTS. DCMs are not customized for individual DHCTs. All DOCSIS-capable
DHCTs within the span of control of a QPSK or CMTS DOCSIS MAC domain
receive the same DCM. The QPSK or CMTS DOCSIS MAC domain is the smallest
level of granularity by which DCMs can be defined. DCMs cannot be defined for
individual DHCTs. In a network in which the DAVIC and DOCSIS systems are
overlaid, the DCM through each path must be consistent as seen by a receiving
DHCT.
After initialization, the operator can change the mode of a DHCT from the DNCS by
After initialization, the operator can change the mode of a DHCT from the DNCS by
changing the DCM on the QPSK or CMTS and sending a DCM Updated message.
When the DHCT receives a DCM Updated message, the DHCT attempts to establish
an interactive data communications path per the DCM setting in the next
UNConfigIndication message it receives if the communication mode is different
from the current setting in the DHCT.
Unless the DHCT has received a DCM Updated message, the DHCT will ignore any
Unless the DHCT has received a DCM Updated message, the DHCT will ignore any
change in the communication mode after it has successfully established an
interactive communications connection.
Only DOCSIS-capable DHCTs can process the DCM setting that the DNCS operator
Only DOCSIS-capable DHCTs can process the DCM setting that the DNCS operator
defines on the DNCS. DAVIC-only DHCTs ignore the setting and continue to
operate in DAVIC mode.