ADTRAN Cable T1 ESF CSU ACE, Руководство пользователя

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Chapter 1. Introduction
61203025L1-1 T1 ESF CSU ACE User Manual 1-9
operation to confirm continued correct functioning. The
background tests include the standard background network
performance monitoring as required by ANSI T1.403 andAT&T
54016, for which the results are stored.
Loopback Tests
A number of different loopbacks can be invoked locally from the
front panel, by T-Watch commands, or remotely by using special
inband codes (AT&T network loop-up and loop-down codes).
Additionally, the loopbacks can be remotely controlled by out-of-
band commands using the T1 ESF FDL, or from T-Watch using a
modem connection. A discussion of network loopbacks and DTE
interface loopbacks follows.
Network Loopbacks
There are two types of network loopbacks: line loopbacks and
payload loopbacks. These are illustrated in Figure 1-4.
• Line Loopback - Loops all of the received data back toward the
network. The transmitted data is the identical line code that
was received, including any bipolar violations or framing
errors.
• Payload Loopback - Similar to line loopback, except that the
framing is extracted from the received data and then
regenerated for the transmitted data.
Figure 1-4. Network Loopback Tests