Cisco DNCS System Release 2.7 3.7 4.2 Guia Do Desenho
1-28
Introducing DOCSIS
4000358 Rev B
DHCT Response to System Interruptions,
Continued
How a DHCT Operating in Mixed DOCSIS/DAVIC Mode Responds to the Loss of the DOCSIS or DAVIC
Channel
This section describes how a DHCT operating in Mixed DOCSIS/DAVIC mode
responds when it loses its DOCSIS or DAVIC channels.
Loss of the DOCSIS Channel
A DHCT operating in Mixed DOCSIS/DAVIC mode responds to the loss of the
Loss of the DOCSIS Channel
A DHCT operating in Mixed DOCSIS/DAVIC mode responds to the loss of the
downstream DOCSIS signal in the following ways:
•
•
The DHCT monitors its last-good downstream DOCSIS frequency until expiration
of internal timeouts. It then scans the entire DOCSIS spectrum to locate and use a
DOCSIS signal with which it can establish an interactive connection.
•
The DHCT continues to receive DBDS broadcast data over the downstream
DAVIC out-of-band QPSK channel.
•
The DHCT does not attempt to establish an interactive DAVIC connection.
•
The DHCT maintains audiovisual services and does not disrupt these services
when the downstream DOCSIS signal is recovered and an interactive connection is
restored.
Because the loss of the DOCSIS channel in Mixed DOCSIS/DAVIC mode represents
a loss of interactive communications only, the DHCT can still provide analog, clear
digital, and subscription digital services, IPPV, RPPV, OOB SI updates, SAM
updates and IPG updates. Purchased VOD events in progress continue
uninterrupted only if the interactive session timeout value is longer than the DOCSIS
channel interruption. However, the subscriber cannot fast-forward, pause, or rewind
the program while the interactive communication is lost. Interactive applications and
new VOD event purchases will also not function.
Loss of the DAVIC Channel
A DHCT operating in Mixed DOCSIS/DAVIC mode responds to the loss of the
Loss of the DAVIC Channel
A DHCT operating in Mixed DOCSIS/DAVIC mode responds to the loss of the
downstream DAVIC out-of-band QPSK signal in the following ways:
•
•
After a timeout period, the DHCT attempts to find DBDS broadcast data on
another downstream DAVIC out-of-band channel by scanning the DAVIC QPSK
spectrum.
•
The DHCT maintains audiovisual services, and does not disrupt these services
when the downstream DAVIC out-of-band QPSK signal is recovered.