4-10
Diagnostics
GDC 048R154-000
Network Payload Loopback
The Network Payload Loopback function provides a data path for a
test signal that is originated and checked at the remote site. The
Payload Loopback, illustrated in Figure 4-6, loops back onto the T1
line only the receive DS0s that carry DTE channel data. The loopback
occurs at a point within the DSU at which the data has already passed
through most of the network interface circuitry.
You can command the loopback by means of either the terminal
interface screen or the front panel switches:
•
On the terminal interface Diagnostic Selection screen this function
is selection
[3] Start Network Payload Loopback
.
You can command the payload loopback from the terminal
interface regardless of how DSU hardware configuration switches
are set.
•
The Network Payload Loopback function is performed as part of
the DTE Local Loopback when DSU hardware configuration
switch S10-4, LL Switch Mode, is set to Bilateral (Off). Figure 4-
18 shows how to perform the DTE Local Loopback using the front
panel switches.
The payload loopback can also be initiated by a loop code transmitted
to the local DSU from the remote site. Local DSU optioning
determines whether it can be commanded into the loopback by the
remote. For the DSU to accept the remote payload loop code, set
switches S14-5 & -6 to 5 On, 6 Off.
