DSU Operations
5-253610-A2-GB41-60 March 1999
Digital Test
Digital Test (DT) is used to check the functionality of a
pair of DSUs or DBMs and the data circuit between the
pair.
The local DBM transmits the 511-bit test pattern over
the network to the remote DBM for an operator-specified
length of time (Figure 5-10). The remote DBM receives
the test pattern and loops it back to its transmitter before
the DTE interface, and returns it to the local DBM. The
test pattern is then passed to the DSU’s comparator to be
checked for errors. At the conclusion of the test, the local
DBM releases the remote DBM from Digital Loopback.
When a Digital Test is performed on a specific port,
data transmission is not affected on the other ports. When
CBrdg or AggrSwitch is enabled, the test is performed
over the DDS link, not the dialed link.
NOTE
The Digital Test command is not
available when the LPDA-2
configuration option is enabled.
For a DSU operating in single-port mode and having
either nondisruptive diagnostics or rate adaption in effect,
an additional selection for Aggr (Aggregate) or Prt1
(Port 1) appears.
Selecting Aggr allows only the test pattern data to
propagate the looped data path. In-band secondary
channel transport data is not allowed to avoid disrupting
in-band secondary channel transport communications.
Selecting Prt1 allows both the test pattern and in-band
secondary channel transport data to propagate the data
path; in-band secondary channel transport
communications are preserved.
NOTE
If the Bilat Lpbk (Bilateral
Loopback) configuration option is
enabled, requesting a Digital Test
on a port automatically initiates a
DTE Loopback on the port as
well. Requesting an aggregate
Remote Digital Loopback
automatically initiates a DTE
Loopback on
all
of the ports.
NOTE
A control DSU can originate a
Digital Test in a point-to-point or
multipoint network, whereas a
tributary DSU can originate a
Digital Test in a point-to-point
network only.
A Digital Test can also be run on a DBM, over a
backup connection, or to a remote DBM for point-to-point
testing. On a DBM-V, DBM-S or DBM-D, a Digital Test
can be run over a backup connection to a remote DBM for
multipoint testing.
To access the Digital Test from the top-level menu,
make the following selections:
•Local (F1)
•Test
•DBM (select active core)
•DT
•Start
•Port Select (when not operating in single-port
mode)
•Trib Address (multipoint control DBM only)
•Run Time (duration of the Digital Test)
For TDM or MCMP mode, the following additional
menu appears:
F1
Port Number:
Prt1 Prt2 Prt3
F2 F3
Prt5 Prt6 AggrPrt4
For a single port DSU, Prt1 and Aggr are the only valid
choices.