ISDN Demonstrator User’s Manual
40-400-00011, Rev. B
22
with most terminals attempting to do the same, and operation resumes
normally.
However, some terminals are designed to report link failures to their Call
Control Layer, which may then attempt to recover. If their recovery procedure
is not satisfied before various timers expire, they may clear (or dump) any
active calls.
Some terminals do not attempt to recover from data link failures, but simply
terminate operation. These devices must be momentarily disconnected from
the Simulator, then reconnected to initialize them. Other terminals may have
a reboot function hidden in an Administration menu.
If a terminal is operated when simulation is halted, the device may store
(queue) the Call Control packets in its memory until simulation is resumed
and its link controllers have restarted. All stored Call Control Messages are
then sent in rapid succession to the Simulator.
Other terminals may respond to a Layer 3 failure by refusing to operate.
These, too, must be reinitialized or rebooted.
Note: ISDN-BRI devices are not normally designed to be stopped and started
at Layer 2 or 3. Consequently, not all terminals will operate in a predictable
manner after simulation is resumed. When in doubt, press RESTART, then
reinitialize the devices.
Various test conditions and configurations can cause frequent line errors and
low-level protocol violations. When using a real ISDN-BRI line, the Central
Office accumulates these errors and discontinues service after a
predetermined limit is exceeded. The Simulator attempts to continue service
even though there are errors.
After testing with a particular configuration known to cause errors, it is good
practice to RESTART the Simulator and reinitialize any connected equipment
before commencing the next test.
Restart
Press the RESTART key to reinitialize Simulator interfaces, to clear all calls
and data link controllers, and to load new provisioning settings. When the
STATUS LED on the front panel illuminates a solid green, the Simulator is
ready.
If any devices are attached via an NT-1 to the U interface, allow time for the
U-SYNC light to turn a solid green. After synchronization, reinitialize any
attached devices, either by removing and re-attaching them (power-up
initialization), or by restarting the controlling application program.
