Objectives; Overload Protection; Overload Indicators - Nortel Meridian SuperNode SL-100 Reference Manual

before it can be processed. However, the data store available for these queues
is limited. When traffic peaks, the messaging load generated may overflow the
available message buffers for call processing. Without overload controls, this
shortage of resources in the IPE during overload may cause arbitrary or
universal degradations in service. If the overload reaches an extreme, the IPE
may become unstable and drop activity. Therefore, overload controls are
necessary for an IPE to reduce the possibility of running out of message buffers
and maintaining the stability of the IPE during overload.

Objectives

The purpose of this feature is to provide overload control for IPEs. The goals
are to:
• provide best possible performance and maintain as high a throughput as
possible to an overloaded IPE
• prevent a minor overload condition from sustaining and causing an
overloaded IPE to become unstable
• attempt to bring an overloaded IPE out of an overload situation as soon as
possible
• provide an overload control system for IPEs that imposes only minimal
data store and real time impact on overloaded IPEs (resources are critical
during overload)
• report overload condition and loss of messages to central controller (CC)
To meet these objectives, the overload control for IPEs is composed of the
following components:
•

overload protection

•

overload indicators

The functionalities of these components, overload protection, and overload
indicators are described next.
Overload protection
The key to overload protection is to regulate the message flow between an IPE
and its host XPM to achieve the first four objectives of this feature.
The preventive measure is a one-step approach: origination shedding. The
origination shedding is a strategy to postpone processing new calls sent from
an overloaded peripheral to prevent the use of any more resources on new calls.
The resources saved are reserved for calls in progress.
This task is performed by the XPM instead of the IPE due to the lack of call
processing information such as call processing state of a terminal and the
insufficient data store to handle complex overload control queuing structures
Meridian SuperNode MSL-100 Intelligent Peripheral Equipment (IPE) Reference Manual MSL14
Feature implementation 6-9