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COMSPHERE DualFlow Data Service Units
E-2 December 1996 3615-A2-GB20-20
Dial Backup for
Received Data Errors
Application
In this application, the router controls backup of one
drop on the Frame Relay or DDS network. When the
router detects data errors, it raises DTR on its secondary
port (which is connected to the DSU’s EIA-232-D/V.24
interface), and lowers DTR when the DDS line is restored.
The DSU monitors the DTR lead on its EIA-232 interface;
it initiates backup when DTR is raised and drops backup
when DTR is lowered.
Automatic DDS line restoration is supported using this
configuration as long as the router’
s secondary port is
configured for backup when data errors are received, and
there is a DualFlow DSU at both the control and tributary
sites. Figure E-1 shows an example of this application.
Select the Synchronous Backup for either a control or
tributary (SyBC or SyBT) configuration from the preset
configurations provided by the Configuration (Confg)
branch, depending upon which DSU you are configuring.
User data travels through the DSU’
s V
.35 interface and
backup data travels through the DSU’s EIA-232-D/V.24
interface. The DSU’
s V
.35 interface is connected to the
router’s primary or active serial port, while the EIA-232
interface is connected to the router’
s secondary serial port.
If your DualFlow DSU is equipped with a Switched 56
DBM, the DSU must be close to the router
. The EIA-232
cable length cannot exceed 34 feet using shielded cable or
68 feet using unshielded cable if backup is to be
supported.
Figure E-1. Dial Backup for Received Data Errors (SyBC and SyBT) Application