Quality of service (QoS) is possibly the single most important feature to deploy to ensure a successful VoIP system. This section defines and describes why QoS is needed and explains how to configure and deploy a QoS solution using both the Modular QoS Command Line (MQC) and AutoQoS.
QoS is defined as
The ability of the network to provide better or “special” service to a set of users and applications at the expense of other users and applications.
Voice and video traffic is very sensitive to delayed packets, lost packets, and variable delay (jitter). The effects of these problems manifest as choppy audio, missing sounds, echo, or unacceptably long pauses in the conversation that cause overlap, or one talker ...