COMSPHERE 3600 Series Data Service Units
1-26
July 1999
3610-A2-GB91-90
External Dial Backup Configuration
An external dial backup unit (DBU) can be used to
provide backup for a point-to-point DSU (e.g., using a
3800 Series dial/lease modem). Aggregate switching is
used to bridge data between the DTE and the external
DBU). Using this configuration, the external DBU is
connected to the DSU’s aggregate port via a standard
crossover cable (see Figure 1-8).
There are two methods used to automate control of the
aggregate switch. Data terminal ready (DTR) lead control
is used when the remote site is expected to initiate the
call, and data set ready (DSR) lead control is used when
the local site is expected to make the call. The Aggregate
Switch (AggrSwitch) configuration option is enabled
using either method.
NOTE
The
external DBU must not be
configured so that the DSR lead is
forced on. This will force the
aggregate switch to be turned on.
When the remote site is expected to initiate a dial
backup session, the DSU’s Answer External Backup
(AnswExtBU) configuration option is enabled. When
enabled, the data terminal ready (DTR) lead on the
aggregate port is monitored so that the 3600 Series DSU
can set up a dial backup session when it receives an
incoming call from the external DBU. When the DTR
lead has been active for at least one second, which means
that the external DBU has established a call and the
external DBU’s data set ready (DSR) lead has been turned
on, the DSU switches the DTE’s data path from the DDS
line to the aggregate port. When the external DBU
disconnects, it turns the DSR lead off, which then causes
the DSU’s DTR lead at the aggregate port to be turned off.
When the DTR lead has been off for at least one second,
the DSU switches the DTE data path from the aggregate
port back to the DDS line.
Figure 1-8. External DTE Lead Control of Backup
Содержание COMSPHERE 3610
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