Cisco DNCS System Release 2.7 3.7 4.2 Design Guide
4000358 Rev B
Introducing DOCSIS
1-29
DHCT Response to System Interruptions,
Continued
The loss of the DAVIC channel in Mixed DOCSIS/DAVIC mode means that DHCT
broadcast and CA data is unavailable to the DHCT, unless the DHCT can receive it
over DOCSIS. The interactive data connection over the DOCSIS channel remains
intact. Whether the DHCT has DBDS broadcast data or not, analog, clear digital, and
subscription digital services will continue to function, and purchased IPPV and VOD
events that are already in progress will continue uninterrupted.
If the DHCT does not have any DBDS broadcast data, new IPPV event purchases
If the DHCT does not have any DBDS broadcast data, new IPPV event purchases
will only succeed if the appropriate GBAMs were cached by the DHCT prior to the
DAVIC channel interruption. RPPV events, OOB SI updates, SAM updates and IPG
updates will not function. Interactive applications including new VOD event
purchases may or may not work, depending upon their use of broadcast data.
How a DHCT Operating in DOCSIS Mode Responds to the Loss of the DOCSIS Channel
This section describes how a DHCT operating in DOCSIS mode responds when it
loses its DOCSIS channels.
Loss of the DOCSIS Channel
A DHCT operating in DOCSIS mode responds to the loss of the downstream
Loss of the DOCSIS Channel
A DHCT operating in DOCSIS 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
DSG-enabled DOCSIS signal with which it can establish an interactive connection.
•
If DBDS broadcast data is unavailable on any DOCSIS channel, the DHCT scans
for a downstream DAVIC out-of-band QPSK signal and uses this, if present, to
receive DBDS broadcast data while the DBDS broadcast data over DOCSIS is
unavailable.
•
The DHCT does not attempt to establish an interactive DAVIC connection.
•
The DHCT maintains audiovisual services and does not disrupt these services as
the downstream DOCSIS signal is recovered and an interactive connection is
restored.
Analog, clear digital, and subscription digital services will continue to function, and
purchased IPPV events in progress will continue uninterrupted. The purchased VOD
events in progress will continue uninterrupted 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.