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Master/Slave CSU
Option
OPERATION
Do not attempt to access another CSU or the master
PMC-100 while a CSU is waiting for confirmation of
your last entry (indicated by the prompt Are You
Sure? (Y/N) displayed at the bottom of the screen). If
you do, you must repeat the process of accessing it.
Refer to the PMC-100 manual for additional PMC-100 operating instruc-
tions.
The master/slave CSU option provides control over using the Supervisory
terminal to configure the CSU. A master CSU allows configuration via
the Supervisory terminal, while a slave CSU prevents it (changes can be
made only via option switches). Any number of CSUs in the network can
be masters or slaves. There are two means of communication between the
Supervisory terminal and a CSU's Supervisory port:
• In-band communication — the primary means of communicating with
the CSU, utilizing PMC-100s and a dedicated multiplexer channel (i.e.,
a permanent virtual circuit, or PVC). In-band communication is in-
tended for monitoring the CSU's performance reports and performing
other non-disruptive diagnostics and maintenance functions. A typical
in-band communication path is illustrated in Figure 2-4.
• Out-of-band communication — the alternate means of communicating
with the CSU, that does not depend on the T1 link to the CSU. Out-of-
band communication with the CSU is typically made via modems or a
Supervisory terminal co-located with the CSU. It is intended for per-
forming diagnostics that would disrupt in-band communication
as a loopback) and for accessing the CSU when a T1 link failure pre-
vents in-band communication. A typical out-of-band communication
path is illustrated in Figure 2-5.
You cannot make configuration changes to a slave CSU, regardless of the
communication path, that could disrupt in-band communication. A slave
CSU displays a warning message when the user attempts to configure it
or perform a self-test or loopback, although it does not prevent these tests.
Use only out-of-band communication for performing
diagnostics that disrupt in-band communication. These
include self-tests and all loopbacks. A slave CSU dis-
plays the warning message WARNING:
To Inband Communication when you attempt to
perform a self-test or loopback: Proceeding with the
diagnostic can result in inaccurate data on the terminal
or complete loss of communication.
3-7
CAUTION
CAUTION
(such
Interfering
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