428 Maintenance
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 havedifferent maximum
thresholds of traffic and have differentways 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.

Normal resolutions

The following are possible resolutions:
•If the D-channel pack (such as MSDL) has multiple D-channels on it,
the D-channel CPU might be unable to sustain the maximum traffic,
especially if both or all D-channels peak at the same time. If this traffic
level is sustained long enough, it can result in an MSDL0304 error
message.
•If the IP trunk card that houses the C-channel card (DCHIP Leader) also
acts as Leader or Backup Leader for the node,it can become severely
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
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