Principles of Operation
4-553610-A2-GB41-60 March 1999
When digital sharing is used on a multipoint circuit,
make sure there is no overlap of LPDA-2 tributary
addresses.
NetView-Initiated Dial Backup
The 3600 Series DSUs support NetView-initiated dial
backup in a point-to-point configuration only
(Figure 4-42). A DBM must be installed. The dial backup
may be automated by the 3600 Series DSUs or initiated
from NetView, NMS, or the DCP.
The 3600 Series DSUs continue to respond to and
process the LPDA-2 commands as a DSU. By enabling
the SNA Backup configuration option (discussed in the
LPDA-2 Configuration Options section of Chapter 5), the
DSU is allowed to respond to the LPDA Call Out and
Disconnect LPDA-2 commands. The Call Out command
instructs the DSU to set up dial backup from the control
site and switch to the PSTN line. The Disconnect
command terminates (disconnects) the PSTN call at the
control DSU and returns data to the DDS line.
For extended circuit configurations, the extended
circuit link can also be configured to respond to NetView
dial backup commands by turning on SNA Backup at the
extended control DSU.
When in dial backup, the 3600 Series DSUs operating
with the SNA Interface option continue to support the
DSU/CSU and Line Status and Transmit/Receive Test
commands. The DSU/CSU and Line Status test monitors
both the PSTN and DDS facilities, and reports whether
the circuit is in dial backup or communicating over the
DDS line.
Figure 4-42. Dial Backup with LPDA-2 Configuration