XtendLan XL-GDB series User’s Guide
2.8 Diagnostics
In addition to the real-time, non-disruptive performance monitoring discussed in Section 2.4, the
XL-GDB System provides for disruptive (out-of-service) diagnostic testing. For detailed
Loopback points, please refer to Appendix D Loopback Diagram. The XL-GDB system does this
by incorporating four loopback modes as follows:
2.8.1 Near End Loopback (NearEndLB)
In this mode, The NLB capability is set up inside STU-C/STU-R as close as possible to the
network side interfaces. The NLB is capable of control (activation and deactivation) by CID. The
received signal is sent to the loop during the NLB is activated. For example, if Near End Loopback
is activated at STU-C, the direction of Near End Loopback would be like (A) in figure 2.1.
STU-C
Figure 2.1 Near End Loop Back
2.8.2 Local Loopback(LocalLB)
The local loopback capability is set up inside STU-C/STU-R as close as possible to the loop
interfaces. The local loopback is capable of control (activation and deactivation) by CID. The
received signal is sent to the loop during local loopback. For example, if local loopback is activated
at STU-C, the direction of local loopback would be like (B) in figure 2.2
STU-C
Figure 2.2 Local DSL Loopback
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Summary of Contents for XL-GDB101E
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