Dte Loopback; Digital Loopback; Remote Digital Loopback; Bilateral Loopback - Paradyne COMSPHERE 3550 Series User Manual

COMSPHERE 3550 Series Data Service Units
NOTE
To issue a Local Loopback to a
tributary DSU , the DSU must
have a DBM installed or a
Conflict w/ Environ message will
appear. The DBM is required to
call the tributary and abort the
Local Loopback.
If the NMS is to abort the
loopback, the tributary's DBM
must be in Idle or Standby mode.
If in Dial Backup mode and the
NMS issues the Abort command,
the command will not be
recognized. The loopback will
have to be aborted from the
DSU's control panel.

DTE Loopback

DTE Loopback (DTE) loops back the data path at the
DTE interface on a per-port basis without affecting the
operation of the remaining ports. This loopback is used to
verify that the DTE connection and the cable are good.

Digital Loopback

Digital Loopback (DL) allows manual testing of the
remote end of the circuit. Data coming in is immediately
transmitted back. For example, a Digital Loopback may
be required in order to complete an external bit error rate
test (BERT) from the remote DSU. The local DSU
receives test data, loops it back to the transmitter before
the DTE interface, and returns it to the network.
Digital Loopback can also be initiated by receiving a
V.54 pattern to go into Digital Loopback. Enable
configuration options V.54 Lpbk (V.54 Loopback) and
RespondRDL (Respond to Remote Digital Loopback).

Remote Digital Loopback

Remote Digital Loopback (RL), sometimes referred to
as RDL, typically supports testing using an external
device, like a protocol analyzer that is connected to the
local DSU's DTE interface. A test message from the
external device is looped back from the receiver to the
transmitter in the remote DSU and returned to the local
DSU.
4-10
In Remote Digital Loopback, the local DSU (control or
tributary) puts the remote DSU into Digital Loopback. A
control DSU can originate Remote Digital Loopback in a
point-to-point or multipoint network, whereas a tributary
DSU can originate Remote Digital Loopback in a
point-to-point network only.
When a DSU (control or tributary) originates Remote
Digital Loopback, both the originating DSU and the
targeted DSU enter Test mode. No other test can be run at
the originating DSU or the targeted DSU until the Remote
Digital Loopback is aborted.
The DSU does not generate test results.

Bilateral Loopback

Bilateral Loopback (Bilat Lpbk) is a combination of
DTE and Digital Loopbacks operating simultaneously in
the same DSU. Both Bilateral and Digital Loopbacks are
selected from the General (Gen) option set.
If Bilat Lpbk is enabled,
requesting a Remote Digital
Loopback or Digital Test will
automatically initiate a DTE
Loopback, as well.

Digital Test

The Digital Test (DT) checks the functionality of a pair
of DSUs and the data circuit between them. This test can
also be run on a DBM over a backup connection to a
remote DBM for point-to-point testing.
The remote DSU is placed in Digital Loopback, then
the local DSU transmits the 511-bit test pattern over the
network to the remote DSU for an operator-specified
length of time. In a multipoint network (where only a
control DSU can originate a Digital Test), tributary DSUs
not involved in the test are placed in Test mode for the
duration of the test.
During the test, the TXD, RXD, and RTS LED
indicators show the states of the leads at the DTE
interface. At the conclusion of the test, the local DSU
releases the remote DSU from Digital Loopback.
July 1999
NOTE
3550-A2-GB20-40