For background information on various traffic analysis concepts and features that are applicable to Voice over IP (VoIP), see Traffic Analysis for Voice over IP 
. This document presents fundamental traffic theory, several statistical traffic models, application of traffic analysis to VoIP networks, and an end-to-end traffic analysis example.
Use the Cisco Communications Manager Capacity Tool 
to calculate the minimum number of active subscribers that are required to support a given installation. Inputs consist primarily of quantity and usage information on the various device types that are supported in a Cisco Unified Communications Manager system.
The following third-party traffic engineering tools are provided for your reference:
