ISDN Demonstrator User’s Manual
40-400-00011, Rev. B
21
CHAPTER 4:
DEMONSTRATOR OPERATION
This section refers to the operation of the ISDN Demonstrator in more detail.
Many users of the Simulator will not need to read this section.
When power is first applied to the Simulator, a self-test is performed and the
interfaces are initialized. The front panel status LED will alternate between
red and green while performing the internal self-test. This takes about 30
seconds after which the status LED turns to a solid green if the self-test
passes successfully. Each interface is continuously polled to determine if any
devices are connected. The U-SYNC LED is displayed when the initialization
of the U port is complete.
The Layer 2
Data Link Controllers
are then reset to the
TEI Unassigned
state
and all data link variables are set to zero. Finally, the Layer 3 Call Control
database is erased, Simulator configurations are loaded, and the Simulator
waits for the arrival of signaling packets on the D Channel.
When the Simulator is processing D Channel packet traffic in this way, the
keypad’s STATUS LED is illuminated a solid green, which signals that the
Simulator’s ports now offer ISDN-BRI services.
When simulation begins, any terminals or communications devices
connected to the Simulator must request TEI’s and establish Multiple Frame
operation before they can transfer Layer 3 Call Control packets to the
Simulator. The first Call Control Message sequence performed is usually the
SPID initialization procedure for acquiring an Endpoint ID.
The Simulator performs ISDN-BRI Call Control using all essential Messages
and Information Elements defined for National ISDN-1and the AT&T
5E(option) series switch.
NOTE: Layer 2 Disconnected Mode is supported
only when initiated by Terminating Equipment. Layer 1 deactivation and
phantom power reverse polarity are not implemented.
All functions of a circuit-switched call are performed, which includes applying
in-band tones and completing B Channel connections. D Channel X.25
Virtual Circuit packet mode calls are also supported. Calls may be originated
from either line (called a Port) and may terminate at either line. Up to 5 end-
to-end calls may be placed simultaneously.
A diagram illustrating a typical end-to-end ISDN-BRI Call Control Message
exchange is shown in Chapter 5.
When Call Control Messages are sent to or returned by the Simulator, the
Message type is displayed under the applicable Port and Directory Number.
Some terminals send a
Link Monitor
Receiver Ready packet every 30 to 60
seconds to confirm the integrity of packet operation during periods of
inactivity. If simulation is halted when this occurs, the terminal will attempt to
restart the Simulator’s link controller supporting that terminal. When
simulation is continued, the Simulator successfully renegotiates data links
