System Performance Under Heavy Load; Message: Pri241 - Nortel 1000 Description, Installation And Operation Manual

Maintenance Page 565 of 644

System performance under heavy load

When the system and IP Trunk 3.01 (and later) are carrying traffic
approaching the maximum sustained levels, there can be short bursts of traffic
exceeding the maximum threshold level. This is caused by the randomness of
call starts. When the maximum threshold levels are exceeded, error messages
are printed to the system screen. In extreme cases, it can cause call loss.
The different components within the system each have different maximum
thresholds of traffic and have different ways of measuring and reacting to
those traffic levels. Most components, such as the D-channel card in the
system and the IP trunk card, have the capability to discard messages when
necessary. These recovery methods can be mitigated by proper system
engineering, but cannot be avoided completely. For example, random calls
can create situations where more messages attempt to travel down the
D-channel than the D-channel can handle. The D-channel has a fixed
maximum bit-rate. When that maximum is exceeded, messages are discarded.
The effects of this recovery process usually appear as certain error messages.
These error messages can be viewed by checking log messages on the system.
The following error messages occur when narrow (peak) bursts of traffic or
messaging exceed the maximum sustained rate by a significant margin,
resulting in call failure or signaling failure.

Message: PRI241

Description
PRI241 is defined as a protocol error where no response to the PRI call
occurred at the far end.
Normal cause
Peak traffic caused either the system D-channel or the IP trunk card to discard
messages.
IP Trunk Description, Installation, and Operation