Specifications

Engineering Guidelines
220
Maintaining Availability of Connections
The quality of service for signalling measures how long a user needs to wait before a service
becomes available, or whether the user becomes blocked from using a function. For example,
delays in receiving dial tone, or blocking that occurs if there are insufficient PSTN trunks degrade
the quality of service.
Quality of service can be ensured by proper provisioning. The sections below provide more
information on traffic guidelines and bandwidth calculations, and IP Networking and
compression.
System Capabilities
As the system grows and traffic increases, it has to deal with more tasks, resulting in slower
feature interaction. ICP systems are engineered to ensure that with different combinations of
devices, services are still maintained within normal working parameters. The exact details are
not captured here, but are specific to particular releases, since changes in software or hardware
have a bearing on the results.
Use of the System Engineering Tool is recommended to ensure that the expected configuration
is within the capabilities of the selected 3300ICP controller, or network of 3300ICPs.
Traffic and Bandwidth Calculations
The level of traffic that the units need to handle has the largest effect on performance and
availability. A number of areas are affected by traffic:
• Trunks to PSTN
• E2T (Gateway) channels
• DSP channels
• LAN blocking between devices
• WAN blocking between endpoints.
See “Provisioning for Traffic” on page 56 for the traffic guidelines used to calculate system
performance.
You can calculate the amount of TDM traffic that needs to be presented in terms of CCS and
match this to a number of trunk channels. With IP, fixed channels do not exist, so this calculation
is more complicated.
To calculate the amount of traffic that can be handled over a LAN or WAN link, apply the
bandwidth calculations in the section “Bandwidth availability” on page 171. Use these to work
out the number of voice channels and assign a particular CCS rating.